Legarra A, Ramón M, Ugarte E, Pérez-Guzmán M D, Arranz J
NEIKER, Basque Institute of Agricultural Research and Development, Apartado 46, Vitoria-Gasteiz, 01080 Spain.
Animal. 2007 Mar;1(2):205-12. doi: 10.1017/S1751731107657826.
The economic weights for somatic cell score (SCS) have been calculated using profit functions. Economic data were collected in the Latxa breed. Three aspects have been considered: bulk tank milk payment, veterinary treatments due to high SCS, and culling. All of them are non-linear profit functions. Milk payment is based on the sum of the log-normal distributions of somatic cell count, and veterinary treatments on the probability of subclinical mastitis, which is inferred when individual SCS surpass some threshold. Both functions lead to non-standard distributions. The derivatives of the profit function were computed numerically. Culling was computed by assuming that a conceptual trait culled by mastitis (CBM) is genetically correlated to SCS. The economic weight considers the increase in the breeding value of CBM correlated to an increase in the breeding value of SCS, assuming genetic correlations ranging from 0 to 0.9. The relevance of the economic weights for selection purposes was checked by the estimation of genetic gains for milk yield and SCS under several scenarios of genetic parameters and economic weights. The overall economic weights for SCS range from - 2.6 to - 9.5 € per point of SCS, with an average of - 4 € per point of SCS, depending on the expected average SCS of the flock. The economic weight is higher around the thresholds for payment policies. Economic weights did not change greatly with other assumptions. The estimated genetic gains with economic weights of 0.83 € per l of milk yield and - 4 € per point of SCS, assuming a genetic correlation of - 0.30, were 3.85 l and - 0.031 SCS per year, with an associated increase in profit of 3.32 €. This represents a very small increase in profit (about 1%) relative to selecting only for milk yield. Other situations (increased economic weights, different genetic correlations) produced similar genetic gains and changes in profit. A desired-gains index reduced the increase in profit by 3%, although it could be greater depending on the genetic parameters. It is concluded that the inclusion of SCS in dairy sheep breeding programs is of low economic relevance and recommended only if recording is inexpensive or for animal welfare concerns.
已使用利润函数计算了体细胞评分（SCS）的经济权重。经济数据收集自拉查羊品种。考虑了三个方面：大罐奶支付、因高SCS导致的兽医治疗以及淘汰。所有这些都是非线性利润函数。奶支付基于体细胞计数的对数正态分布之和，兽医治疗基于亚临床乳腺炎的概率，当个体SCS超过某个阈值时可推断出该概率。这两个函数都导致非标准分布。利润函数的导数通过数值计算得出。淘汰是通过假设一个因乳腺炎而淘汰的概念性性状（CBM）与SCS存在遗传相关性来计算的。经济权重考虑了与SCS育种值增加相关的CBM育种值的增加，假设遗传相关性范围为0至0.9。通过在几种遗传参数和经济权重的情况下估计产奶量和SCS的遗传进展，检验了经济权重对于选择目的的相关性。SCS的总体经济权重范围为每SCS点 -2.6至 -9.5欧元，平均为每SCS点 -4欧元，这取决于羊群预期的平均SCS。在支付政策的阈值附近，经济权重更高。经济权重在其他假设下变化不大。假设遗传相关性为 -0.30，每升产奶量的经济权重为0.83欧元，每SCS点为 -4欧元，估计的遗传进展为每年3.85升和 -0.031 SCS，利润相应增加3.32欧元。相对于仅选择产奶量而言，这代表利润的非常小的增加（约1%）。其他情况（经济权重增加、不同的遗传相关性）产生了类似的遗传进展和利润变化。期望增益指数使利润增加减少了3%，不过根据遗传参数可能会更大。得出的结论是，将SCS纳入奶羊育种计划的经济相关性较低，仅在记录成本低廉或出于动物福利考虑时才建议纳入。
