Production, reproduction and some adaptation characteristics of Boran cattle breed under changing climate: A systematic review and meta-analysis

Introduction Climate change affects livestock production and productivity, which could threaten livestock-based food security in pastoral and agro-pastoral production systems of the tropics and sub-tropics. Boran cattle breed is one of the hardiest Zebu cattle reared by Borana Oromo pastoralists for milk and meat production. However, there is limited comprensive information on production, reproduction and adaption traits of the Boran cattle in Ethiopia. Thus, this paper aims to compile the main production, reproduction and some adaptation traits of Boran cattle based on systematic review and meta-analysis of peer reviewed published and unpublished literature. Methodology A combination of systematic review and meta-analysis based on PRISMA guideline was employed. Accordingly, out of 646 recorded articles identified through database searching, 64 were found to be eligible for production, reproduction and adaptation characteristics of the Boran cattle, 28 articles were included in qualitative systematic review while 36 articles were used for quantitative meta-analysis. Result The Boran cattle breed has the ability to survive, produce and reproduce under high ambient temperature, utilize low quality forage resources, and resist water shortage or long watering intervals and tick infestations. The review revealed that the breed employs various adaptation responses (morphological, physiological, biochemical, metabolic, cellular and molecular responses) to cope with harsh environmental conditions including climate change, rangeland degradation, seasonal feed and water shortages and high incidences of tick infestations. The meta-analysis using a random-effects model allowed provision of pooled estimates of heritability and genetic correlations for reproduction and production traits, which could be used to solve genetic prediction equations under a population level in purebred Boran cattle. In addition, heritability and genetic-correlation estimates found in the present study suggest that there is high genetic variability for most traits in Boran cattle, and that genetic progress is possible for all studied traits in this breed. Conclusion The Boran cattle breed has the ability to survive, produce and reproduce under high ambient temperature, utilize low quality forage resources, and resist water shortage or long watering intervals and tick infestations. However, currently there are several challenges such as recurrent droughts, pasture deterioration and lack of systematic selection and breeding programs that play to undermine the realization of the potential of the breed. Thus, we recommend systematic selection for enhancing the reproductive and production performances without compromising the adaptation traits of the breed coupled with improved management of rangelands.

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Introduction 9
Climate change has devastating effects on livestock production and productivity, which could 10 threaten livestock-based food security in pastoral and agro-pastoral production systems of the 11 tropics and sub-tropics. Hence, to sustain livestock production in an environment challenged by 12 climate change, the animals must have the ability to survive and produce under extreme 13 conditions. Boran 86 We conducted a combination of systematic and meta-reviews as the methodology of qualitative 87 comparative analysis (QCA). To do this, we used the actual published studies as our data (rather 88 than the data used by each study), and this enabled us to pool non-standardized and qualitative 89 information[8] for adaptation traits while for production and reproduction parameters [5] 90 quantitative parameters were pooled to obtain estimated mean values.The implementation of the 91 systematic and meta-reviews followed the Preferred Reporting Items for Systematic Reviews and   confidence interval, would then be back transformed to correlation for presentation [12]. The 149 approximate normal scale based on Fisher's Z transformation [12,13] is as follows: in the jth article. To return to the original scale, the following equation [12] was used:

Heritability and genetic correlation 174
Meta-analysis was performed on the basis of a random-effects model [12], in which the parameter 175 estimates for all traits were analysed by assuming independence and normality. the degree of heterogeneity among studies (τ 2 ) for each trait can be described as follows: Where Q is the Q statistics [18] given by Where wj is the parameter estimate weight (as the inverse of published sampling variance for the    spend more time standing so that they can reorient themselves in different directions to avoid direct 297 solar radiation and ground radiation. In addition, the standing position also obstructs the 298 conductive heat transfer into the animal body due to the presence of a layer of air adjacent to the 299 skin, and also facilitates the dissipation of body heat load to the surroundings by increasing the 300 amount of skin exposed to air flow or wind.       showing that there is larger phenotypic variation in these traits than in others (Table 2).    In Ethiopia, breeding mainly relies on natural service and, therefore, acceptable bull fertility is also 511 critical [5]. Factors that determine a bull's fertility and performance include plane of nutrition [5],  Table 3 indicates comparative summary of birth weight (BW) and mature weight (MW) of six 532 Ethiopian cattle breeds. Boran cattle had better performance in both growth traits (Table 3).

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Additionally, performance of Boran has been substantially improved through improvement in

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Carcass characteristics differ between breeds and are influenced by the plane of nutrition and 557 production system [86]. Selection for these traits is greatly influenced by the market demand. In 558 the Ethiopian context, export markets demand lean meat whereas when the target is local market, 559 23 fattened cattle are required [5,86]. Therefore, the breeding, feeding and other management 560 conditions should be designed in such a way that the requirements of the specific market are met.   is less compared with exotic and cross breeds, the level of production of Boran cattle is relatively 590 stable during harsh conditions where high producing animals are at risk [1]. Furthermore, during 591 periods of extreme heat stress, water scarcity and reduced pasture availability, they maintain their 592 reproductive potential due to their smaller body size whereas the larger exotic animals may face 593 reproductive impairments which could be attributed to their higher maintenance energy 594 requirements [5,20].   Heterogeneity among studies were moderate in milk yield traits by I 2 index (50 to 75%) and higher 624 in reproduction, growth and milk composition traits with I 2 index (>75%). These results reinforced 625 the importance of accounting this heterogeneity in selecting random effect model in the meta-626 analysis reviews of the studies (Table 4).

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The weight and milk production performances of Boran

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Genetic-correlation estimates with the respective 95% confidence interval and the I 2 index to 649 quantify the degree of heterogeneity among the studies were shown in Table 6 for each trait pairs.   (Table 6). Estimated genetic correlations among some reproduction and production traits in these 664 studies are in line with summary of genetic correlations of fertility and production traits for tropical 665 zebu cattle in East Africa (Table 7). Except for correlation between AFC and CD, the other  Birth and mature weight 0.63 [95] Weaning and yearling weight 0.86 [95] Weaning and final weight 0.71 -0.99 [95,102] Weaning and mature weight 0.94 [95] Yearling and final weight 0.85 [95] Yearling and mature weight 0.43 [95] Final and mature weight 0.75 [95] Although genetic correlations estimated in the present study were in favour of the common 672 objectives of genetic improvement programs of Boran cattle in relation to climate change 673 adaptation, it is important to re-estimate the genetic parameters in regular intervals, especially if 674 selection of different traits is made simultaneously [5]. There are no conflicts of interest for the preparation of this manuscript.  1   2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33 At t