Evaluation of reproduction performance and calf sex ratio of dairy cattle in selected locations of South-East Oromia

Dairy farmers in many parts of the world complain about the deviation from the normal calf sex ratio following Artifi cial Insemination (AI). The prospective and retrospective studies were conducted to compare the sex ratio of the calves born following Artifi cial Insemination (AI) and Natural Mating (NM) under institutional and smallholder-managed dairy farms. This study also compared the reproductive performance of dairy cattle under institutional management and smallholder systems. The data encompassed farm records maintained between 1996-2014 G.C by dairy farms at Arsi University-Asela, crossbreeding center at Gobe ranch, and Agarfa ATVET College. These farms reared both F1 and crossbreds with higher (>75%) exotic inheritances (grade crosses). The study also considered household and progeny history surveys on smallholder dairy farms (n=90) adjoining to the institutional farms which were randomly selected from Tiyo, Kofele, and Sinana districts. The result indicates that most of the respondents at Tiyo (96.8%) and Kofale (100%) were concerned about the differences in the sex ratio of calves born from AI service and natural mating, while most of the respondents at Sinana (29%) did not report such differences. The respondents in Tiyo and Kofale districts reported higher numbers of male calves (58%) and higher numbers of female calves (58.1%) born from cows inseminated artifi cially respectively. The Average Age at First Calving (AFC) had no signifi cant difference between genotypes (F1 and grade crosses) reared at the institutional farms. There were signifi cant differences (p<0.05) in AFC across the ranches. The AFC was lower in the institutional farms when compared to those managed at smallholder management conditions. The number of services per conception (NSC) varied p<0.05) across the dairy farms. No signifi cant differences were observed among the sex ratio of the calves born through natural and AI mating systems either at the institutional or smallholder farms. However, differences due to season and year were observed, indicating the effect of non-genetic factors infl uencing the sex ratio of the calves. In some seasons the numbers of male calves were higher while the reverse was true for some other seasons. Therefore, the reproduction traits of the cattle differed (P<0.05) across the institution and smallholder production systems having lower values observed among the cattle raised at the dairy farms and higher for the F1 crossbred than grade crosses, while production trait of the cattle differed (P<0.05) across the three dairy farms and there were no signifi cant differences in calf sex ratio among the calves born from AI and NM. Thesis Evaluation of reproduction performance and calf sex ratio of dairy cattle in selected locations of South-East Oromia


Introduction
Ethiopia is reported to possess the largest livestock population in Africa. The total cattle population for the country is estimated to be about 55.0 million heads [1]. The indigenous breeds accounted for 98.7% of the total cattle of the country with a minuscule number of crossbreds, [1].
Despite the large cattle population, the average productivity of the cattle in the country is dismally low. This may be attributed to several factors, which are both non-genetic and genetic, The non-genetic factor includes a shortage of fodder supply, disease, low level of management, and lack of proper breeding management practices. These constraints result in poor production and reproductive performance of dairy cattle [2,3]. This often leads to longer days open (postpartum anoestrous), late age at fi rst calving, extended calving interval, besides shorter lactation length, and low milk production [4]. The overall effi ciency of dairy cattle is infl uenced by factors such as delayed age at fi rst service, undetected oestrus, a higher number of services per conception, prolonging the calving interval. These results in higher replacement costs because of the fewer number of calves born in the lifetime of the cows [5].
In Ethiopia the mating is panmictic and the overall effi ciency of Artifi cial Insemination (AI) is dismally low [6]. Studies by [7] have indicated that at the national level the overall effi ciency of AI service is as low as 60 %, which is lower than most of the developing countries.
In addition to reproduction traits, dairy farmers are also concerned about calf sex ratios. Theoretically, the average calf ratio (Secondary Sex Ratio, SSR) under normal circumstances is 50% for both sexes [8]. However, there have been complaints from the cattle rearers that there is a deviation from the normal calf sex ratio. Although Artifi cial Insemination (AI) is an important technique for genetic improvement of low producing dairy cattle, farmers in many parts of the world complain about its effect on calf sex ratios. Still, the development and use of AI has revolutionized cattle production and genetic improvement, particularly and its impact has been revolutionary in the dairy sector. As indicated in a study by [9] it was reported that the Irish farmers prefer natural mating over AI as they believe that in doing so the probability of female calf increases in dairy herds. According to [10] indicated that the sex ratio was 48:52, (female: male) for calves born from AI, while it was 55:45 (female: male) for calves born from natural mating. Generally, the sex shift towards female calves was with a numerical difference by 10% when natural service was used, but it did not show a statistical variation.
In Ethiopia too, a study by [7] from the Mekelle area indicated that the sex ratio was favoring the birth of bull calves when the cow was inseminated.
According to [11] indicated that, unlike natural mating, AI does not affect calf sex ratio as widely perceived by smallholder dairy producers in Ethiopia. Therefore, dairy farmers who started using AI to improve their dairy genetics and those who tend to use it in the future should not bother about the effect of AI on calf sex ratio. Based on this hard evidence, AI should Overall, there have been no satisfactory explanations as to why there is skewness observed among the sex ratio of mammals. Some of the reasons are hormone levels, fetal mortality exhibited by individual dams causing the deviation from the expected 1:1 ratio. Perhaps the skewed sex ratios exhibited by some bulls were due to coital frequency [20,22]. That is, bulls with increased sexual frequency could have produced a sex ratio that differed from bulls with a decreased sexual frequency (i.e number of male offspring produced decreased with increased mating). It is reported that dairy cows, but not heifers, on a high plane of nutrition give birth to proportionately more male than female calves than cows on a poorer diet [23].
The ability to alter the secondary sex ratio in cattle is economically attractive. There has been a growing concern about the determination of the sex ratio of calves born in dairy cattle. Dairy farmers prefer cow calves to perpetuate their herd while crossbred bull calves are desired in beef production.
The desired male to female sex ratio (i.e., lower sex ratio) in dairy cattle is fulfi lled when the female replacement rates are high. The fi nancial attraction to manipulate sex ratio viz.
It was suggested by [24] that alteration of sex ratio through biotechnological applications such as superovulation, in vitro fertilization, in vitro embryo production, embryo division, and embryo transfer can be benefi cial for the dairy industry. In the long-term, the profi tability of a dairy enterprise may be enhanced with more numbers female calves being born.
There has been growing concern from the agrarian community about the sex ratio favoring male calves in herds where AI is prevalent, however, to date no satisfactory explanation has been put forward on the relationship between the reproductive performance of dairy cows and differences in calves' sex ratios for calving following natural vis-à-vis AI insemination. Thus, this study was conducted to assess the reproductive performance of cattle reared in the study areas and the effects of natural vs artifi cial insemination on the calf sex ratio.

General objective
• To evaluate reproductive performance and calf sex ratio in selected institutional and smallholder dairy farms in southeast Oromia.

Specifi c objectives
• To assess farmers' perception of calf sex ratios in the study area • To assess the reproductive performances of crossbred and indigenous dairy cows managed at selected institutional and smallholder dairy farms.
• To assess the effect of the mating-type (natural and artifi cial insemination) on calf sex ratios in established dairy farms and study the factors.

Literature review
Dairy production systems: In Ethiopia, cattle are reared under different farming systems viz. pastoral, agro-pastoral, and crop-livestock farming systems. However, the milk production system can be broadly classifi ed into urban, periurban, and rural milk production systems [25]. The urban and peri-urban milk production system, include small and large private farms situated in the urban and peri-urban areas are mostly commercial in nature and rear crossbred animals having the potential to produce around 1120-2500 liters of milk /lactation. This production system is now expanding in the highlands of the country and among the mixed croplivestock farmers [25]. The traditional smallholder system, roughly corresponding to the rural milk production system and accounts for 97 percent of the total national milk production and 75 percent of the commercial milk production [26].
The traditional smallholder farming system is grossly dependent on indigenous breeds, which by and large have low productivity and comprise native zebu cattle. These native cattle have a lactation yield of around 400-680 kg of milk /cow [27]. The erstwhile state dairy farms, (now being privatized or in the process of privatization), use grade animals (those with more than 87.5 percent exotic blood) and are mostly concentrated with in100 km distance around Addis Ababa.
The Ethiopian highlands possess a high potential for dairy development. These areas occupying the central part of Ethiopia, over about 40% of the country (approx. 490.000 km 2 ), and are the largest of their kind in sub-Saharan Africa [28]. In the highland areas, the agricultural production system is predominantly substance smallholder mixed farming, with crop and livestock husbandry typically practiced within the same management unit. In this farming system, all the feed requirement is derived from native pasture and a balance comes from crop residues and stub grazing.
The majority of milking cows are indigenous animals that have low production performance with the average age at fi rst calving is 53 months and the average calving intervals is 25 months. Cows had three to four calves before leaving the herd at 11-13 years of age, the average caw lactation5 yield is 524 liters for 239 days of which 238 liters is offtake for human use while 286 liters is suckled by the calf. But also a very small number of crossbred animals are milked to provide the family with fresh milk butter and cheese. Women, who use the regular cash income to buy household necessities or to save for festival occasions, sell surpluses, usually. Both the pastoralist and smallholder farmers produce 98% of the country's milk production [2].
Traditional crop/livestock farms in rural areas: These farms are located between 25 and 130 km of Addis Ababa. They are small farms with an average of four dairy cows and provide very little or no specialized inputs to their dairy enterprise. They sell fresh milk daily to the government-owned Dairy Development Enterprise (DDE). Excess milk is processed into butter and local cottage cheese, ayib, and sold in local markets.

Intensifi ed dairy/crop-livestock farms
These are smallholder farms located around Addis Ababa and exercise some form of an intensive dairy production system. These farms have had experiences with dairy development projects under the Ministry of Agriculture. Projects such as the Selale dairy development project and the smallholder dairy development project have been operational in these areas and have infl uenced the production system. Improved genotypes, artifi cial insemination, improved forages, concentrate feeding, housing, calf bucket feeding, and early weaning are common practices by farmers.
Compared to those traditional crop/livestock farmers, landholding is about half the size and milk production is about 15% higher, but the number of cows per household is similar.
Crop/livestock farms with intensive cropping: These farms are located relatively closer to Addis Ababa city, between 25 and 60 km. The farms and herds are 25% larger than the traditional crop/livestock farmers. The cropping system is more intensive and often uses fertilizers. They provide supplementary feeds to their animals. Fresh milk is sold to the DDE and they seldom practice making dairy products. Intra-urban dairy farms in Addis Ababa: These dairy farms are specialized and intensive production units based on zerograzing of crossbred and high-grade cows. There is no or little grazing within the city and stall-feeding is based on purchased hay and concentrates. The level of exotic blood in the herd is highest, annual milk production per cow is high, and milk is directly sold to the local market.
Urban dairy in secondary towns: These are specialized dairy farms found in most secondary towns within the milk shed.
In these small towns, farmers have more access to grazing; stallfeeding is, therefore, less intensive. The level of exotic blood in the herd is high, but herd size is the smallest and averages about two cows per farm. Milk is sold fresh to local markets or the DDE, processed into butter and ayib, and sold.
Most farm owners have off-farm activities representing about two-third [6].

Artifi cial insemination service in Ethiopia
In Ethiopia, AI was introduced in 1938 in Asmara (the current capital city of Eritrea), which was interrupted due to the 2 nd World War and restarted again in 1952 [29]. However, it was again discontinued due to unaffordable expenses of importing semen, liquid nitrogen, and other related inputs requirement.
In 1967, an independent service was started in the Arsi Region, Chilalo Awraja under the Swedish International Development Agency (Sida). Artifi cial insemination services were introduced at the farm level over 35 years ago [30].
The present National Artifi cial Insemination Center (NAIC) was established at Kaliti, Addis Ababa in 1984 to coordinate the overall AI operation at the national level [31].
The effi ciency of the service in the country, however, has remained at a very low level due to several constraints viz.
infrastructure, managerial, and fi nancial, besides poor heat detection of the cattle by the benefi ciaries, improper timing of insemination, lack of inseminators and also embryonic death [2].

Feed resources for dairy cattle
The urban and peri-urban dairy operations depend specifi cally on the herbal pasture hay as a source of roughage feed within the critical highlands of Ethiopia [32]. The predominant roughage feed assets for dairy animals throughout all the special manufacturing structures consist of herbal pasture/ grasslands, grass hays, crop residues, and non-conventional feed sources [33][34][35]. The crude protein content material of pastures most often is lower than 7%, which couldn't guide the protection necessities of ruminants [26]. Good grass and legume hays are adequate for preserving maximum training of livestock, in particular those in a non-effective kingdom [36]. Therefore, dairy cows which depend upon poor fi ne basal feeds will now not express their full genetic capacity. According to [35], agro-industrial by-products which include bran, middling, oilseed cakes, and molasses are fed as a supplement to crossbred dairy cows in urban and peri-urban areas.

Reproductive performance of dairy cows
Reproductive traits identify characters, which infl uence the overall reproduction effi ciency of the cattle especially those related to the female reproductive system. These traits include age at fi rst calving, calving interval, days open, and several services per conception. [37,38] reported that herd profi tability is determined by the reproductive performance of the dairy cows, as it correlates with the numbers of lactation and also the numbers of replacement herd. Furthermore, studies by [39] indicated that the major factors infl uencing reproductive performance include management both at the herd and individual cows [3] reported that in tropical countries the performance of cattle at the smallholder level is infl uenced by several factors viz. genotype, location (geographical location), the season of calving, suckling status (of the calves), parity, and body condition score). According to [32]

Non-genetic factor affecting reproductive traits
Season of calving: Season of calving has an important impact on reproductive traits, as the high temperature increases respiratory rate and severely depresses feed intake.
A signifi cant effect was detected for the season of calving on reproductive traits [46,47].

Nutrition
Nutrition is considered a reproductive problem in dairy herds; two factors should be kept in mind about the relationship between nutrition and reproduction. Malnutrition on one hand is only one possible cause of reproductive problems.
Factors like poor estrus detection and poor hygiene at calving should be ruled out before looking for nutritional causes of breeding problems. Secondly, relatively little is known with certainty about the complex interaction between nutrition and reproduction [48].
Factors associated with a negative energy balance have been considered as causes of reproductive failure. Lower conception rates, longer calving intervals, and an increased incidence of silent heat have been considered the results of energy defi ciency [49].
Excessive energy intake during late lactation and dry periods can lead to "fat cow" problems. Over-conditioned cows have a higher incidence of retained placenta, more uterine infections, and more cystic ovaries. They also have more metabolic disorders, which again can result in poor reproductive performance [50,51] indicated that body condition scoring is, recommended to assess the nutritional status of dairy cows during the reproduction cycle.
Phosphorus defi ciency has been most commonly associated with decreased reproductive performance in dairy cows.
Anoestrus delayed sexual maturity, and low conception rates have been accounted for when phosphorus intake was low. A major concern in mineral feeding of dry cows relates to providing optimum levels of calcium and phosphorus to decrease the occurrence of milk fever. In a study of 33 herds, cows with milk fever were 4.2 times more likely to require assistance at calving, 2 times more likely to have retained placenta, and 1.6 times more likely to be treated for metritis [48].

Dairy housing
A suitable dairy housing and husbandry system should meet the fundamental needs of cattle, based on the principles of sound animal care. According to [51] there are three predominant goals of environmental management in dairy herds:-Reduce the absolute number of pathogens in the environment, reduce the potential for contact between the pathogens and the cows, minimize the detrimental effects of the environment on the animal, which may modify the host defense mechanism.
Dairy herds' problem during housing is the lack of enough space for each group of animals according to age and production. The need to group cows, based on the reproductive and/or production group system, becomes rapidly apparent in large herds. Some of the most important reproductive problems associated with the design of facilities and management of the environment can be summarized as follows [51].
Inadequate space for each group of animals in the herd may result in overcrowding and thus increases the risk of spread of infectious diseases and problems with nutritional management.
Inadequate housing facilities can limit the detection, identifi cation, and handling of cows in heat, resulting in sub-optimal reproductive performance. Cows calving in well-bedded calving pen are less prone to traumatic injuries associated with slipping, falling, and decumbency secondary to parturient paresis. Inadequate and insuffi cient manure disposal can lead to environmental contamination and increase the risk of spreading infectious diseases.

Sex ratios of calves
According to [52] sex ratio theory is defi ned as the ratio of male-to-female offspring at birth, the sex ratio is an evolutionarily developed feature of the norm of 50:50 and does not have objective refutations. In livestock production, the possibility to modify the sex ratio of the calf can result in a substantial increase in the production of livestock farms [53] that the manipulation of sex ratio can sensibly enhance the effectiveness of selection and genetic improvement programs, through the differential increase in the numbers of males or females calves being born. as well, the sex of the calf is considered the most important genetic trait for animal production as it exerts a profound infl uence on several factors such as growth rates, milk production, and susceptibility to diseases. As it is a genetic trait, the sex of the unborn cannot be manipulated by genetic selection, but only through sex predetermination methods.
As indicated in a study by [54], selection for particular sex is currently possible only by pre-implantation diagnosis and transfer of embryos of a given sex, by prenatal diagnosis and abortion of undesired sex, or through sperm separation using fl ow cytometry combined with in-vitro fertilization (IVF). However, the cost and clinical nature of preimplantation diagnosis and IVF limit their use, especially in developing countries.

Factors affecting calves sex ratios
Calves sex ratio can be affected by diverse genetic factors maternal infl uence geographical location of the concerned farm, dominant weather patterns, timing and frequency of coitus (relative to ovulation), diet of the dam; paternal age, parental age gap, maternal blood type, Body Condition Score (BCS), vaginal pH have all been statistically associated with an altered secondary sex ratio (SSR) in mammals [8].
Timing of service may also contribute to the difference in secondary sex ratio between mating types. Although a consensus has not been reached in the scientifi c literature on the effect of timing of service on sex ratio some studies have reported a higher proportion of female offspring following early insemination, which would predominantly occur with natural mating.

Effect of genetic
According to [23], genetic variation in sex ratio (male offspring as a proportion of total births) can be sought at various levels. The genetic differences could exist among species (which would not be of particular concern to livestock producers) or among breeds, strains, lines, families, or individuals. Also, crossbreds or strain or line crosses could differ among themselves or from their straight bred parents in the sex ratio of the offspring

Effect of maternal infl uence
Some maternal features such as body condition, diet, blood glucose level, dominant status in the herd, estrogen, testosterone levels, stress and age of the dam, parity, litter size, and some female-linked parameters such as time of insemination, the side of the active ovary, exposure to contaminants and environmental temperature have been suggested to alter sex ratio [8].
Correspondingly [55] accounted that the sex ratio of embryos at the expanded blastocyst stage was more than 75% male when glucose was included in the medium, whereas the sex ratio did not deviate signifi cantly from 1:1 in the glucosefree medium. Concerning vaginal pH, there was a strong negative correlation between vaginal pH and sex ratio during the early and late stages of the fertile cycle in hamsters. near the beginning of the fertile cycle, when the pH was the least acidic, the number of male offspring produced was the least.
On the contrary, late in the fertile cycle, when the vaginal pH was most acidic, the number of male offspring was the greatest [56].
According to [57] there seems to be no indication that the age of the parents had any particular effect on the sex ratio of the offspring.
In Ethiopia, the rainy months and the fi rst month of spring are characterized by critical feed scarcity in terms of both quantity and quality. Calving of more female calves to cows that showed estrus during this season of the year is in agreement with the theory of [58]who suggested that organisms that experienced negative energy balance or face environmental shocks tend to give more births to female offspring.
The effect of dam parity on calf sex is at odds with previous fi ndings where no association between calf sex and dam age or parity was evident in dairy cows [8] or humans [59] Nonetheless, maternal age was reported to positively infl uence secondary sex ratio in other studies across species, which is in line with trends observed in the present study [60] reported different secondary sex ratios in purebred Angus calves from heifer dams (male: female ratio = 50:50) or cow dams (ratio male: female = 51:49). The positive effect of parity on sex ratio in the present study may refl ect the [58] hypothesis, which stated that mothers in poorer physiological conditions or with limited resources would be advantaged by investing more heavily in the more reproductively stable sex (i.e., the female).
[61] suggested that parental care can infl uence the breeding success of one sex. Studies by [62] indicate that in Red deer the sons of the dominant mothers are more successful than their daughters are, whereas, the daughters of subordinate mothers are more successful than their sons. Similarly [63] reported that these effects occur partly because of the breeding effi ciency of males.
studies have indicated that sexual dimorphism favors the females in times of food shortages, the juvenile females have better survivability than the males during such periods, it may be because the nutrient requirements of the males (for growth) is higher than the females [64].

Effect of sibling competition
Studies by [65] suggested that, if sons and daughters are equally costly to the rear but siblings of one sex are more likely to compete for mates than are those of the other sex, the sex ratio of progeny should be biased toward the sex that will compete less intensely. Besides [66] also stated that under these conditions the production of a large proportion of females not only reduces mating competition between siblings but is likely to increase the mating success of the male siblings. According to [55] changes in the intensity of sibling competition or the degree of inbreeding would favor changes in the sex ratio.

Effect of breeding method
There have been several reports highlighting the differences in sex ratio attributable to that of the method of breeding.
Results of a study by [67] from Pakistan indicated that the numbers of male calves born were higher (P<0.05) amongst the dams inseminated artifi cially.
Similarly, a study by [68] indicated that there is a high incidence of male calves being born among the cows inseminated artifi cially. One contributing factor may be the effect of timing of mating on the resultant sex ratio. Nevertheless, other studies in cattle have failed to identify a relationship between time of service and sex ratio. However, the results of a study by [11] from Ethiopia did not show any signifi cant deviation in calf sex ratio among the cows inseminated artifi cially, however they did mention that the sex ratio favored the female-born calves under natural mating conditions.

Effect of nutrition
According to [69] there can be an alteration in the sex ratio in mammals under natural selection. They hypothesized that under favorable conditions the chances of male offspring being born are higher than those of female offspring [60] their study indicated that the dams maintained on a high plane of nutrition would be able to invest more heavily in their offspring than those on poor nutritional planes thus altering the sex ratio.
Selective abortion takes place favoring the female offspring at different stages of gestation among dams raised on the poor plane of nutrition [9,11].
Effect of the season beyond the immediate feed supply can indicate an innate evolutionary adaptation whereby climatic variables, which are related to feeding supply can also, infl uence peri conception selection of embryos based on their sex.
According to [70] indicates that the calving season has a slight effect on the sex ratio of the calves. Similarly, studies by [8] indicated that the probability of a bull being born increased with increasing air temperature and humidity around the time of conception. Studies by [68] indicate that there were more numbers male calves born in the monsoon and winter months when compared to the summer months. This may be because winters and monsoons are more comfortable when compared to summer and there may be the selective abortion of a male fetus in summers due to environmental stress. It has also been reported that during the summers the feed quality and feed consumption of the dams decreased, the male fetus has higher growth and weight rate when compared to the female fetus. Thereby the nutrient requirements are higher and hence selective abortion of the male fetus occurs during the stressful months.
Similarly, some psychological disorders of mammals are known to have a pronounced annual rhythm [70], indicating climatic effects. Weather factors are said to be positively associated with the SSR. The effect of climate is known to infl uence forage production and the levels of estrogens in some leguminous plants [71,72].
Similarly, a study by [73,74] demonstrated that a signifi cant effect of pre-conceptual maternal diet on the sex ratio, female mice fed a very high saturated fat diet had signifi cantly more male offspring than either control or restricted fat diet females.

Effect of population dynamics
According to Sharpe and Wyatt (1974) and Burley (1980), the sex ratios of offspring vary with population demography, including the juvenile sex ratio the adult sex ratio [13] population density (Emmerson, 1948), the phase of the population cycle [52] the size of the maternal lineage of the mother [75] and the extent of mortality among male and female juveniles in the previous season. If the cows are subjected to harassment by the bulls, then there are chances that it can infl uence the calf sex ratio favoring the birth of more male calves due to selective abortion of the female calves. However, these random fl uctuations are more commonly observed in small populations [62].

Description of the study area
The study was conducted in three woredas and three selected institution dairy farms and one kebeles of smallholder dairy farms from each woreda situated in the vicinity of the selected farms, these kebeles were selected in a way that the climatic variation between the farms and the kebeles were minimum. The institution dairy farms were Agarfa ATVETC dairy farm, Arsi University dairy farm, and Gobe dairy cattle ranches. In addition to farm records used from the three institutions' dairy farms, a questioner-based survey was also carried out to assess the response of some selected smallholder dairy farmers towards the studied topic Figure 1.

Arsi University dairy farm
The dairy farm of Arsi University was established in 1979.G.C. for a distribution-crossbred heifer, provision of artifi cial insemination (AI) service, and forage production and marketing. The current herd size of the farm is 239 cattle with different age groups and having 57-99% blood levels. The farm is situated at 07º 33`09" N latitude and 39º15`37" E longitude, at an altitude of 2804 m.a.s.l. The average annual rainfall in Assela town is reported to be 1120 mm, while the average mean minimum and maximum temperatures were recorded to be 7.8 ºC and 18.9 ºC, respectively [76].

Gobe dairy cattle ranch
The

Sampling techniques
Farm record: Data on the sex ratio of the calves born at the farms, and its relationship with the type of mating (natural or artifi cial), production, and reproduction records of the cows over the parities were used from the three institution dairy farms. Only the data of the cows with complete information were included in the study.

Farm record data
The reproduction and production-related data maintained from 1996-2014 G.C. at the respective institution dairy farms were used from the pedigree records maintained of the cattle reared at the farms. The reproductive traits of the cattle from

Data analysis
The data collected was analyzed statistically using a statistical package for social science (SPSS) v 16 for Windows.
The qualitative data were tested using Chi-square analysis.
Descriptive statistics were used for the quantitative traits, the means were compared using. One way ANOVA and Duncan's multiple range test and the effect of ages, location, mating type, breed, year, season, and parity on the sex ratio of the calves.
The following general linear statistical models were used: • The fi rst model for the reproductive trait(AFC, DO, CI, NSC)

Institution farms model
Y ijk =μ+ f i +bj+ pk+ s (i.j.k) + e ij Where, μ=over all mean. f i = effect of farm, bj = effect of breed , p k =effect of parity , e ijk =is the error term.

Smallholder farm model
Y ij =μ+ di+ e ij Where μ=over all mean. d i = effect of district, e ij =is the error term.
• Model for production performance (Birth weight ,LL, LMY) Where, μ=over all mean. f i = effect of farm, bj = effect of parity, e ijk =is the error term

•
Model for calves sex ratios (Male:Female)

Institutional farms model
Where μ = is overall means, mi = is type of breeding (AI/ NM), pj= effect of parity, dk= environmental factor (season, nutrition), e ij= is the error term.

Smallholder farm model
Where μ = is overall means, mi = is a type of breeding (AI/ NM), pj= effect of parity, d k = effect of the district, e ij= is the error term.

Household characteristics
The results about the household types, age categories, and educational level of smallholder dairy farmers of the study area are presented in Table 2

Household size
As indicated in Table 3, the mean household size below 15 years was signifi cantly different at (P<0.05) among the three study districts. While those in productive age (16- family size and a maximum value of 11 at Sinana followed by 9 at Tiyo and 8 at Kofale.

Livestock demography and land holdings in the study area
The results about the livestock demography, average landholding, and herd size of the studied locations are presented in Table 4. The fi ndings in the Total Livestock Unit (TLU) indicate that the numbers of oxen were highest at Tiyo followed by the numbers of cows in the herd. The population of the cows was however higher at Kofale, while the population of the oxen and the cows were similar at Sinana. The study further indicates that there were no signifi cant differences in landholding among the respondents in the three locations, while the average herd size varied ( P<0.05) across the locations with the highest herd size reported from Kofele and lowest at Sinana.
Perception of the respondents regarding factors infl uencing calf sex ratio and the type of mating. The results as presented in Table 5 indicate that most of the respondents at Tiyo and Kofale were concerned about the differences in sex ratio (male: female) of calves born from natural mating vs artifi cial insemination while most of the respondents at Sinana district did not observe any signifi cant differences in the sex ratio. The results further indicate that majority of the respondents (P<0.05) at Tiyo thought that the calf sex ratio varied, favoring the birth of the male calves while most of the respondents (who followed the differences in the sex ratio). The respondents from Kofale responded otherwise and while they too observed the differences in the sex ratio, but those favoring the birth of the female calves.
The results as presented in Table 6 indicate that most of the respondents irrespective of all the locations thought that there    are several genetic and non-genetic factors infl uencing the calf sex ratio. The respondents at Tiyo believe that the differences were attributable to the genetic makeup of the animals. There were also people in Tiyo and Kofale who indicated that the season of mating infl uenced the calf sex ratio. The respondents from Sinana were, however, of the opinion that the nutrition received by the cow at the time of mating and thereafter infl uenced the sex ratio of the calf. However, they also observed that some unexplainable reasons were infl uencing the calf sex ratio.
The study further indicated that the method of breeding (artifi cial vis-à-vis natural) too infl uenced the calf sex ratio while the respondents of Tiyo and Kofale indicated that the differences were more when the cows have mated artifi cially ( The results as presented in Table 8  The fi ndings as presented in Table 9, further indicated that there were differences (P<0.05) across the districts, which    The results further indicated that there was no signifi cant difference between calving intervals across all the parties.
The results as presented in Table 10    Production trait of dairy cattle managed under three institution dairy farms. The results as presented in Table 13 pertain to the average birth weight and some production parameters of cattle raised at the three dairy farms. It transpires from the result that the birth weight of the cattle differed (P<0.05) across the three dairy farms irrespective of the parities. The results indicate that the birth weight of the calves was higher at Asela when compared to the other two locations, with the lowest birth weight observed among those born at the Gobe dairy farm.
The results about the lactation length (LL) of the cattle across the parities and reared at the two dairy farms indicate differences with lower LL among the cattle reared at Agarfa dairy farm.
The lactation milk yield only varied (P<0.05) across the current parity with no differences observed in the other two parities. The values being signifi cant among the cattle reared at Agarfa dairy farm.

Calves sex ratios
Effect of method of breeding and parity on the sex ratio of dairy calves: The results as presented in Table 14 indicate that there were differences (p<0.05) in calf sex ratio both between the calves born from natural mating and artifi cial insemination. In both cases, it favored the birth of the male calves at parity1. The results of the method of breeding on the calf sex ratio of the 2 nd parity indicate that there were no differences in the calf sex ratio of the calves born from artifi cial insemination, but higher (P<0.05) numbers of female calves were born from both artifi cial and natural mating. There were no differences in sex ratio among the calves born from the two types of mating. The fi ndings of the method of breeding for 3 rd parity indicate that there were no differences in calf sex ratio across the two types of mating. while the results of the calf sex ratio on the method of breeding for 4 th parity indicate that there were differences (P<0.05) in the sex ratio for calves born from artifi cial insemination and natural mating. The numbers of male calves being higher than the female calves at 1 st and 4 th parities. Natural mating favored the birth of female calves during the 2 nd and 4 th parities.
The results as presented in Table 15 indicate that there

Effect of district and farm type on the sex ratio of calves:
The results as presented in Table 16  The results as indicated in Table 17    Effect of parity, season and year on the sex ratio of calves: The results as indicated in Table 18

Household characteristics
The results as presented in Table 2 indicate that the education status of the respondents was lower than those reported by [78] in the Meket district. Similarly, [79] also indicated that in the Arsi zone, Tiyo, and Bilbilo districts, 52 percent of the households were barely literate. The lower educational levels of the farmers in the area are a bane as it is expected that the farming communities with low education status generally would not be able to manage their

Household size
The household size at study areas was lower than what was reported by [78] from Meket district, who reported that Livestock demography, land holdings, and herd size among the respondents in the study area. The results as presented in Table 4 further indicate that the average livestock ownership per household in the three districts was more or less similar to the values as reported by [81] The livestock holding per household as was observed in this study was lower than those reported by [81] The results also indicate that there was species diversity at the farm, which is a good practice so that they would be able to minimize their risk associated with rearing a particular species alone [81] This also ensures that the feed resources are properly utilized as cattle and sheep are grazers while goats are browsers. This also ensures that there are specifi ed species of livestock for meeting the socio-cultural roles and those to be used for agrarian activities and also for transportation, the fi ndings are in close accordance with those of fi nding.
The average land holdings as indicated in Table 4 are lower than those reported by [82] from the yerer watershed of adaliben woreda. The low landholding as observed in the study limits the numbers of livestock a family can rear effectively, this also indicates that there was limited scope for improving the dairy sector unless or until modern scientifi c husbandry methods are put in place. The use of crop residues and other agro-industrial by-products need to be incorporated along with the traditional grazing system to meet the minimum maintenance requirements of the bovines. The respondents need to be empowered with the techniques of hay and silage preparation so that the basic nutritional requirements of the animals are maintained. The use of modern feeding and husbandry management in the maintenance of herds reared in small landholdings has also been reported by [83] while the average herd size varied (P<0.05) across the locations with the highest herd size reported from Kofele and lowest at Sinana.

Perception of the respondents regarding factors infl uencing calf sex ratio and the type of mating
The results as presented in Table 5  The results as presented in Table 6 further indicate that the perception of the respondents varied signifi cantly while most of them opined that the sex ratio was infl uenced by both genetic and non-genetic factors, these observations are in close accordance with the fi ndings of [8,16,24,58]. However, as observed in the study the respondents could not attribute the observable differences in the sex ratio of the calves due to any specifi c factor that may be a fallout of their poor analytical or recording skills as indicated earlier. Lack of education among the husbandry persons can lead to the poor recording of farm data, which is a big impediment to the development of livestock husbandry in the region.
The result as presented in Table 7 indicates the preferred method of breeding cattle varied across the study areas. While artifi cial insemination (AI) was preferred at Tiyo and Kofale, the respondents preferred natural mating over artifi cial insemination at Sinana. This may be a fallout of the differences in the AI services available in the studied areas. The AI services have not yet penetrated deep in the country and hence many woredas and kebeles are yet to be benefi tted from this bio technique. However, the differences in preference of mating their cattle as observed may also be attributed to the economical advantages/ disadvantages associated with the different methods of breeding, the observations are in close accordance with those of [67] and [68]. The respondents preferred AI over natural mating because of the lack of good bulls in the region and also because of the prestige associated with the rearing of crossbreds at their homestead, the observations are in close accordance with those of [84]. The respondents were also

Reproductive performance of dairy cattle managed under three Institution and smallholder dairy farms
The results pertaining to the reproductive traits of the cattle as observed in the present study in Table 8 indicates that the age at fi rst calving (AFC) was higher among the F 1 crossbreds when compared to those of the grade crosses ( >75% exotic inheritance), the fi ndings are in close accordance with the results obtained by [83]. This may be attributed to inheritance of the HF breed as it has been reported that, the AFC of the Taurus cattle are higher than those of the zebu counterparts [85] The average AFC as was observed among the two genotypes is following the fi ndings of several authors from Ethiopia [86,87].
The results pertaining to the days open (DO) too varied across the genotypes, the average higher values as observed were higher among the graded cattle indicating that the calving interval (CI) too will be higher among such animals. This has a direct consequence on the lifetime production of calves with lower numbers of calves born from cows with longer DO and CI, which is not a desirable trait, similar reports have also been reported by [42]. The higher DO values among the higher crosses may also be attributed to tropical degeneration as have been reported by several authors [5,88], from Egypt, and [77] from Ethiopia where the F 1 crossbreds usually outperform the higher crosses despite lower levels of exotic inheritance.
The differences in CI across the parities may be attributed to the age of the cows where studies have indicated that the reproductive traits usually optimize at the second parity and thereafter a decline is usually observed as the animal ages [43].
This difference in the decline in reproductive performance may be also due to hormonal changes across the age of the cows, which show a decline as the animal ages [89].
The fi ndings from Tables 9,10  locations on reproductive traits has long been observed by [90] who reported that the differences in reproductive traits can be signifi cantly infl uenced by environmental differences attributable to a specifi c location and as the environments may vary across locations it will be observable as location effect.
The differences as observed could also be partially correlated with the management of the animals. However, it has also been reported by [77] that in absence of any records the recall method (as employed here) may not be as accurate especially when the periods are too distant as have been observed in the traits pertaining to the CI. The effect of the year on the CI could be due to the temporal environmental effect. where the quality of the forage usually varies between the years and also seasons with a year, similarly incidences of rainfall and diseases can also affect the CI across the seasons and also across the years the observations are in close accordance with those of [91].
However, the average values of the reproductive traits as were observed in this study are following the fi ndings of several authors AFC [92] DO [3,43].
The results as presented in however, the reverse was true for the NSC. The differences may be attributed to the feed and fodder availability and the management which is expected to be relatively better in the institutional farms, the observations are in close accordance with those of [3,39] who also reported that as the reproductive traits are lowly heritable they respond well to the management of the animals. However the differences in NSC maybe because of the poor oestrus detection in the farms, this may also be partially ascribed to the fact that most of the cattle show signs of oestrus in the night hours when it is very diffi cult to detect the actual animal amongst the herd, the observations are in close accordance with those of [93,94].
The results as presented in Table 12 also indicate that there was a variation (P<0.05) in the reproduction traits across the seasons. The differences as observed may also be ascribed to the genotype by the environmental effect of the cattle and also the managemental program [39]. The AFC is closely correlated with the age at maturity and has been reported to be infl uenced by the season, the presence of good quality of feed and fodder, and low environmental stress [1]. It was observed to be higher among the dry months when there was a defi ciency of fodder and the diurnal temperature was relatively high. High environmental temperatures are associated with the stress of the animals and thereby infl uence the trait [3]. The calving interval (CI) too varied across the seasons, which may be correlated with the normal behavior of the cows, during the main rainy season when the cows may not be able to graze and hence show their normal estrus behavior [48,91]. Moreover, the incidences of silent heat are also higher especially among the grade crosses in the summer months [49]. The higher fi gures for DO and CI also indicates that the overall lifetime productivity in terms of numbers of lactation and calf crop is low have an adverse consequence on the overall economy of the cattle husbandry activities, the fi ndings are in close accordance with those of [95] and [43]. The fi gures as observed for the reproductive traits viz. AFC is within the range of values reported by [84] while those of CI and DO are in close accordance with the observations of [89].

Production trait of dairy cattle managed under three institution dairy farms
The fi ndings as presented in Table 13 indicate that the birth weight of the calves varied across the three organized farms.
The differences may be attributed to several genetic factors, the parity number of the dam, gestation length of the dam, the sex of the calves, genotype/breed of the dam, and the sire, the observations are in close accordance with those of [96]. The birth weight of the calves can also be infl uenced by several managemental factors viz. the availability of feed and fodder, disease incidences in the dam especially during the last trimester of her gestation, similar [97,98]. The average birth weights of the calves across the different parties are in close accordance with the reports of [88]. The lactation length (LL) and LMY of the cows reared at the dairy farms too varied across the parities, these values are infl uenced by the gestation length in the previous parity, CI and DO maternal effect, and also on the health and the genotype of the dam [39].
The environmental factors infl uencing the trait include the management of the cows (feed and fodder), years (seasons across the years), and the outbreaks of diseases or/and parasites [99]. The average values of birth weight of the calves, LL, and LMY as observed are well within the values reported by [100].

Calves sex ratios
Effect of method of breeding and parity on the sex ratio of dairy calves: The fi ndings from  [15,16,64] who also reported the differences in the sex ratio of the calves born across the different parities of the cows. The differences as observed may be attributed to the selective abortion of the calves of a particular sex in certain seasons, which is in line with the resource allocation theory of [58] or also due to the deviation in the hormonal levels in (from the normal values) the cow, which can be infl uenced by several factors including the consumption of phytoestrogenic compounds [71,72].
The availability of feed and fodder usually varies across the seasons and there might be differences in environmental stresses and disease incidences across the seasons, which may lead to selective abortions favoring particular sex over the other [101][102][103].
Therefore, to minimize incidences of abortion in the herd, it is suggested that the community members be provided training on proper management and husbandry practices of cattle, the suggestions are in close accordance with those of [8,104].
Studies by [105] to have indicated that there is a variation in sex ratio (from the expected) among the cows at an older age which again is infl uenced by its parity and is in close accordance with those observed in the study [96,[106][107][108]. The differences are attributable to the levels of sex hormone in the cows the levels of which usually diminish with the age, the fi ndings are in close consonance with those of [17,110,111].
The results as presented in Table 15 indicate that there were observable differences in the sex ratio of the calves across the dairy farms too. The results indicated that higher (P<0.05) numbers of male calves were born in the 3 rd and 4 th parities (irrespective of the type of mating). However, there were no differences among the numbers of male and female calves born due to artifi cial insemination and natural mating.
The observations favor the resource allocation theory [58].
The fi ndings are also in close accordance with those of [15], who reported that there was no signifi cant difference across in the sex ratio of the calves from natural mating and artifi cial insemination. The observations of the agrarian community regarding more numbers of male calves being born from cows mated artifi cially vis-a-vis that of natural mating may be attributed to fl uctuations due to environmental factors alone, abortions, or loss of memory to recall a particular event [88].
The deviation as observed across the farms may, in turn, be due to differences in the availability of feed and fodder and diseases localized to the farm, which may lead to abortions and fetal deaths, thereby swaying away from the theoretically expected sex ratio [8].

Effect of district and farm type on the sex ratio of calves:
The results as presented in Table 16 further indicate that there were differences across locations pertaining to the sex ratio of the calves. The observations are in close accordance with those of [15] who reported localized differences in the sex ratio of the calves that varied across the years. The differences as observed may be attributed to the nutrition received by the cows and during the time of mating as studies have indicated that if the cows received phytoestrogens there can be the selective abortion of the fetus [53,58]. The fi ndings also indicate that there were differences in the sex ratio of the calves across the parities. However, the results were not consistent over the parities and across the locations too. The differences as observed may also be attributed to the causes mentioned ahead, the effect of parity on the sex ratio of the calves born from a cow in different parities have also been reported by several authors [59,82,93,112].
The results as presented in Table 17  seasons especially during the feed stress the numbers of male calves conceived were less when compared to the female calves. This may be due to the selective allocation of maternal resources favoring the birth of the female calves thereby infl uencing the sex ratio in favor of particular sex [15,63,108].

Effect of season and year on the sex ratio of calves:
The results as presented in Table 18 indicate the infl uence of seasonal factors on the sex ratio of the calves. The effect of the season can have both a direct and indirect effect on the overall sex ratio of the calves as observed in the study. The direct consequence of the season can be attributed to the differences in feed and fodder availability and the diseases prevalent among the cows during a particular season which is in accordance with the fi ndings of [113]. While the indirect effect can be attributed to the managemental differences during a particular season when the agrarian community may not have enough feed resources to feed their cows or are busy with other farming-related activities. There are also instances of butting of pregnant cows by bulls and steers, especially in the loose housing system such incidences can also lead to abortions especially among the cows at the fi nal months of pregnancy thereby infl uencing the sex ratio where the chances of a male calf being aborted out are higher than the female calves. Similarly, the tilt in sex ratio can also be due to dystocia-related deaths where the chances of such deaths are higher among the male calves due to their larger size [113]. The hormonal imbalance can selectively abort male fetuses more frequently than those of the female fetus, thereby tilting the sex ratio favoring the numbers of females born [60,[114][115][116][117][118]. The differences in the sex ratio of the cattle attributable to non-genetic factors have been observed in the study reported by several authors [ 27,92].
The effect of year on the calf sex ratio (Table 19) indicates that there were differences in the sex ratio of the calves born at different seasons, which may be a fall out of the differences in management over the years and also on several climatic and seasonal factors discussed ahead [72,[119][120][121][122][123][124][125][126][127][128].

Summary and conclusion
This study was carried out on three selected institution dairy farms and smallholder dairy farms (n=90) in three districts (Tiyo, Kofale, and Sinana) of Oromia regional state.
The result showed that the numbers of oxen were higher than the numbers of cows in the Tiyo district, while the number of cows is higher in the other two districts showing that farmers mainly keep cattle for milk production. From the interviews with smallholder dairy farmers, it was observed that farmers at Tiyo and Kofale districts were concerned about the differences in calf sex ratios (male: female) which they perceived was resulted due to artifi cial insemination, while it was not the case for Sinana district. No signifi cant differences were observed among the sex ratio of the calves born through natural and AI mating systems either at the institutional or smallholder farms. However, differences due to season and year were observed, indicating the effect of non-genetic factors infl uencing the sex ratio of the calves. The reproduction traits of the cattle differed (P<0.05) across the two production systems with lower values observed among the cattle raised at the dairy farms and higher for the F1 crossbred than grade crosses, while production traits of the cattle differed (P<0.05) across the three dairy farms.
From the progeny history survey conducted on smallholder dairy farms, it was observed that the numbers of male and female calves born from natural and artifi cial insemination were different in the three districts. The numbers of male calves being higher than the female calves at 1 st and 4 th parities. The higher (P<0.05) numbers of male calves were born in the 3 rd and 4 th parities (irrespective of the type of mating), with no differences across the types of mating in the three institutional dairy farms.
Furthermore, there were differences in the sex ratio of the calves born at different seasons, across locations, which may be a fall out of the differences in management over the years and also on several climatic and seasonal factors. However not consistent across the farms, which could be attributed to the causes mentioned. The differences in reproductive traits can be signifi cantly infl uenced by environmental differences attributable to a specifi c location and as the environments may vary across locations, it will be observable as location effect. The production traits also varied, this may be due to managements and environments. Therefore, the use of grade-breed cattle in resource-limited areas essentially requires serious preventive procedures. There has been a growing concern about the deviation of the sex ratio of calves born in dairy cattle.
From the overall data, it was observed that there were no signifi cant differences in the sex ratio of the calves born from natural mating vis-s-vis that of artifi cial insemination. However, the effect of locations/ farms, seasons, and year were observed. It was observed that during certain seasons especially during the feed stress times, the numbers of male calves conceived were less when compared to the female calves. Therefore, management practices should be persistent across the year and season to prevent annul and seasonal variability in the sex ratios of calves. Although farmers complain about calf sex ratio, using the overall data in this study it can be concluded that there are no signifi cant differences in the calf sex ratio of the calves born from natural mating vis-s-vis that of artifi cial insemination. The lowest reproduction and production performance observed on smallholder dairy farms compared to the three state farms clearly shows the need for improvement on both institution and farmers aspects.

Statement of author
First, I declare that this thesis is my legitimate work and that all sources of materials used for this thesis have been dully acknowledged. This thesis has been submitted in partial fulfi llment of the requirement for an advanced MSc. degree at Hawassa University and is deposited at the university library to be readily accessible to borrowers under the rules of the library.
I gravely declare that this thesis was not submitted to any other institution anywhere for the award of any other academic degree, diploma, or certifi cate. Finally, I would like to thank Almightily, God, who helped me to fi nish this work.