Browsing by Subject "Genetic improvement"

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Breeding objectives and selection schemes for Boran cattle in Kenya
(2009) Rewe, Thomas; Valle Zárate, Anne
Beef production with Boran cattle of Kenya presents an opportunity for utilising the potential of an indigenous breed. Improving the performance of these cattle through production of quality breeding stock may support the livelihoods of Boran cattle farmers. Organised breeding programmes for Boran cattle in Kenya are lacking. This thesis focussed on the design of optimal genetic improvement programmes for Boran cattle raised in the semi-arid tropics of Kenya. Specifically, the aims were: 1) to review the potential for beef cattle genetic improvement in sub-Saharan Africa, 2) to describe the state of institutional framework supporting Boran breeding in Kenya while considering the different categories of Boran cattle farmers, 3) to investigate the genetic and economic merit of alternative breeding programmes based on improved Boran, the unimproved Boran and the possibilities of expanding an inclusive breeding programme for these two strains of Boran cattle, 4) to discuss the feasibility of alternative breeding strategies within the context of a formal breeding programme in Kenya. The methodological approach entailed a review of the literature on cattle production and genetic improvement strategies for sub-Saharan Africa. This was done by identifying previous and on-going breeding activities among indigenous cattle breeds based on their regional distribution in Africa. An institutional framework analysis to characterise the Boran breeding sector in Kenya was also performed. Open questions were presented to the Boran cattle Breeders? Society of Kenya through an online survey to ascertain the structure of the society in terms of membership, cattle populations and animal breeding activities. The production systems, cattle types and breeding objectives were also sought from previous studies on Boran cattle in the process of developing appropriate breeding programmes. Design and evaluation of nucleus breeding programmes (genetically and economically) was done with the ZPLAN computer programme by defining the breeding objectives and selection criteria traits, describing breeding and commercial populations, describing selection groups as well as their reproduction performance parameters. The costs of the breeding programme included fixed costs and costs of animal recording. To account for genetic gain and the flow of animal genetics, a gene transmission matrix was defined utilising the selection groups alongside genetic and phenotypic parameter matrices. The information sources for the selection criteria were mainly parental selection groups and halfsibs of animal. The number of animals forming the selection groups and information sources was calculated in the NBILD and NUMBER subroutines of the ZPLAN. The interest rates for returns and costs were 8% and 6% respectively while the investment period was set at 25 years. The scope of the study was limited to two classes of farmers keeping Boran, the commercial beef ranchers and the market-oriented low-input beef producers that interact with commercial beef ranchers. Three breeding objectives were evaluated, 1) conventional breeding objectives with market (economic) values derived from bio-economic modelling, namely: direct sale weight, dressing percentage, consumable meat percentage, cow weaning rate, cow survival rate, cow weight, age at first calving, milk yield, feed intake and post weaning survival rate, 2) a combination of selected conventional target traits in addition to traits important to low-input farmers to exploit the ongoing informal interaction between the large scale ranchers and low-input systems, and 3) trait preferences for low-input farmers derived from conjoint analysis studies namely; sale weight, calving interval, temperament, tick resistance, trypanotolerance and lactation milk yield. To evaluate the benefit of perceived trypanotolerance in unimproved low-input herds, strategic recording for trypanotolerance for offspring of nucleus sires born in these herds was assumed. Closed and open-nucleus types were evaluated and variations on the nucleus size (5%, 10% and 25%). proportion of gene transfer to commercial herds (25%, 50%, 70%) and the proportion of gene importation into the nucleus (10%, 20% and 30%) were tested. The results from the institutional framework analysis showed that the Boran sector is structured with a section of the farmers being large scale commercial ranchers keeping approximately 17% of a total population of 580,000 heads of cattle. The rest were Boran farmers operating in low-input production systems keeping over 80% of the total population. The large scale commercial ranchers were found to be divided into two groups, about 52% of these farmers were elite breeders that record with the Kenya Stud Book and the rest were mainly commercial. The large scale commercial ranchers keep the improved Boran while the low-input farmers keep the unimproved Boran. The large scale commercial ranchers were organised into a breed society, namely, the Boran Cattle Breeders Society (BCBS), incorporating both the elite breeders and the commercial group. The BCBS was identified as a key stakeholder in the breeding of Boran cattle because of their informal role as suppliers of breeding stock. The results from the evaluation of alternative open and closed-nucleus breeding programmes utilising the Boran cattle populations were obtained with the ZPLAN computer programme. For the elite breeders?, where a total population of 52,000 cows with a breeding unit of 25% was assumed, the overall monetary genetic gain was KSh86 per cow while the profit per cow was KSh361 under the conventional breeding objective. The breeding programme with the entire BCBS group where a population of 99,972 cows was assumed obtained a higher monetary genetic gain and profit than the elite group per cow of KSh93 and KSh431 respectively under the same breeding objective. The results revealed the effect of a larger effective population size on performance of breeding programmes. The breeding programme based wholly on market oriented low-input producers was evaluated using farmer trait preferences as the breeding objective. This breeding programme posted a negative gain for milk yield of -1.1 kg, which improved when restrictions on growth and adaptation were applied. The introduction of the combined breeding objective that included adaptation and disease tolerance traits resulted in a drop in sale weight gain by almost 2 kg. However, post-weaning survival rate improved from 0.4% to 1% and trypanotolerance gained 20% packed cell volume within this breeding objective. There was reduction in feed intake under the combined breeding objective, which is desirable considering the prevailing limitations on land, feed and climatic conditions. This may induce a change in focus from the continuous improvement in sale weight. The gains in post weaning survival rate would support this objective. The results from the expanded breeding programme may be beneficial to both the low-input farmers and the commercial ranchers because of the advantages conferred from the improvement in adaptation traits. The benefits of extra recording for trypanotolerance in the commercial herds of the expanded programme were not realised. In general, the open-nucleus programmes were superior genetically while the closed-nucleus programmes were superior economically. The larger nucleus sizes (25%), higher gene contributions to commercial herd (70%) and limiting nucleus opening to 10% were most profitable. The limitations of the study were observed from the online interviews with respect to the amount of information that could be retrieved from key persons. Similarly, information on the legal framework of the breeding sector was scarce since Kenya has no active livestock breeding policy. The design and evaluation of the breeding programmes was possible with ZPLAN, however, in this study, genetic variance for traits, which normally diminishes with selection and inbreeding, was not account for. This may have had implications related to overestimation of genetic response and economic returns. Nonetheless, the potential of the Boran for both beef production and fitness traits coupled with the presence of institutional support for animal recording in Kenya were evaluated as strengths of the system. This study has shown the possibilities of combining market and non-market traits useful in breeding programmes for cattle utilised in different production systems. This approach is useful in cases where interactions exist between different categories of farmers. To benefit from advantages offered by open-nucleus breeding, recording may be avoided in the commercial herds and selection be done under criteria that are acceptable by the farmers. Further investigations on farmer organisations and comprehensive livestock breeding policies may aid the process of establishing co-ordinated breeding programmes for Boran cattle in Kenya.