Rewe T O, Indetie D, Ojango J M K, Kahi A K
Animal Breeding and Genetics Group, Department of Animal Science, Egerton University, Njoro, Kenya.
J Anim Breed Genet. 2006 Feb;123(1):23-36. doi: 10.1111/j.1439-0388.2006.00558.x.
Economic values for production (sale weight in steers, SWs, kg and heifers, SWh, kg; dressing percentage, DP; consumable meat percentage, CMP and milk yield, MY, kg) and functional (cow weight, CoWT, kg; cow survival rate, CoSR, %; postweaning survival rate, PSR, %; feed intake of cows, FIc, heifers, FIh and steers, FIs, kg DM) traits were estimated for six production systems utilizing the Boran breed in Kenya. The influence of the estimated economic values on genetic improvement was also assessed using different selection indices. The six production systems were described according to their sale age, levels of input and final goal, namely, short-fed medium input beef (SMB); long-fed medium input beef (LMB); short-fed high input beef (SHB); long-fed high input beef (LHB); long-fed low input dual purpose (LLD); and long-fed medium input dual purpose (LMD). Two evaluation bases were considered: fixed herd size and fixed pasture input. In the fixed herd-size situation, the economic values for production (except MY in beef systems) and functional traits (except FI in all systems) were positive meaning a unit increase in genetic merit of these traits had greater influence on revenues than costs. As expected, the economic value for MY was negative in the pure beef systems (SMB, LMB, SHB and LHB) and positive in the dual-purpose systems (LLD and LMD). When compared with the economic values estimated in the fixed herd-size situation, in the fixed pasture input situation they were lower for feed intake in the three classes of livestock and other traits related to it in all systems. These traits were CoSR, CoWR, PSR, CoWT, SWh and MY. The economic values for CoWT in LLD and LMD were negative (KSh -11.14 and -15.33 respectively). The economic values did not influence much the direction of the genetic response in each trait in the different production systems. However, the magnitude of the actual gain was dependent on the index applied. The magnitude of the economic values for production and functional traits estimated in this study suggest that genetic improvement of these traits will have a positive effect on profitability of Boran cows kept in dual-purpose systems and when herd size is restricted. In beef systems, genetic improvement of MY will have a negative effect on profitability, especially when restrictions on herd size and feed exists.
针对肯尼亚六个使用博拉纳品种的生产系统，估算了生产（阉牛销售体重，SWs，千克；小母牛销售体重，SWh，千克；屠宰率，DP；可食用肉比例，CMP；以及产奶量，MY，千克）和功能（母牛体重，CoWT，千克；母牛存活率，CoSR，%；断奶后存活率，PSR，%；母牛采食量，FIc，小母牛采食量，FIh，阉牛采食量，FIs，千克干物质）性状的经济价值。还使用不同的选择指数评估了估算的经济价值对遗传改良的影响。这六个生产系统根据其销售年龄、投入水平和最终目标进行描述，即短期育肥中等投入肉牛（SMB）；长期育肥中等投入肉牛（LMB）；短期育肥高投入肉牛（SHB）；长期育肥高投入肉牛（LHB）；长期育肥低投入两用型（LLD）；以及长期育肥中等投入两用型（LMD）。考虑了两个评估基础：固定畜群规模和固定牧场投入。在固定畜群规模的情况下，生产（肉牛系统中的MY除外）和功能性状（所有系统中的FI除外）的经济价值为正，这意味着这些性状的遗传价值每增加一个单位，对收入的影响大于成本。正如预期的那样，纯肉牛系统（SMB、LMB、SHB和LHB）中MY的经济价值为负，而两用型系统（LLD和LMD）中为正。与在固定畜群规模情况下估算的经济价值相比，在固定牧场投入情况下，所有系统中三类家畜的采食量及其相关的其他性状的经济价值较低。这些性状包括CoSR、CoWR、PSR、CoWT、SWh和MY。LLD和LMD中CoWT的经济价值为负（分别为-11.14肯尼亚先令和-15.33肯尼亚先令）。经济价值对不同生产系统中各性状的遗传反应方向影响不大。然而，实际增益的幅度取决于所应用的指数。本研究中估算的生产和功能性状的经济价值幅度表明，这些性状的遗传改良将对两用型系统中饲养的博拉纳母牛的盈利能力产生积极影响，并且在畜群规模受到限制时也是如此。在肉牛系统中，MY的遗传改良将对盈利能力产生负面影响，特别是当畜群规模和饲料受到限制时。
