Colleau J J, Le Bihan-Duval E
Institut National de la Recherche Agronomique, Quantitative and Applied Genetics Unit, Jouy-en-Josas, France.
J Dairy Sci. 1995 Mar;78(3):659-71. doi: 10.3168/jds.S0022-0302(95)76678-4.
Mastitis problems were assumed to decrease profitability of dairy cows through milk price, treatment cost, and involuntary culling cost. Milk price decreased through a stepwise function of SCC (actual French conditions). A continuous latent variate was supposed to trigger other costs through appropriate thresholds. The relative weights for one genetic standard deviation in the selection objective were 1, -.07, and -.14 for yield, SCC, and mastitis liability, respectively. Annual genetic gains were predicted for a conventional breeding scheme using statistical parameters from the literature. Selection on yield and log SCC, with or without mastitis culling rate, increased genetic gains for the overall profitability of .7 or .9%, respectively, compared with selection on yield only. Increases of log SCC and mastitis problems because of selection were substantially reduced (40 to 60%). Consequences from constraint of the genetic trend for mastitis liability to zero depended on the method used to assess mastitis problems. Use of log SCC had a significant and variable negative impact (-8.9 to -36% according to parameters) on overall efficiency compared with the relevant unconstrained selection. Simultaneous use of log SCC and culling rate had a moderate effect (-4.9 to -7.4%) on overall efficiency compared with that from unconstrained selection.
乳腺炎问题被认为会通过牛奶价格、治疗成本和非自愿淘汰成本降低奶牛的盈利能力。牛奶价格通过体细胞计数（SCC，实际法国情况）的分段函数下降。一个连续的潜在变量被认为会通过适当的阈值引发其他成本。在选择目标中，每一个遗传标准差的相对权重，产奶量、SCC和乳腺炎易感性分别为1、-0.07和-0.14。利用文献中的统计参数预测了传统育种方案的年度遗传进展。与仅选择产奶量相比，选择产奶量和对数SCC，无论有无乳腺炎淘汰率，总体盈利能力的遗传进展分别提高了0.7%或0.9%。由于选择导致的对数SCC和乳腺炎问题的增加大幅减少（40%至60%）。将乳腺炎易感性的遗传趋势限制为零的后果取决于评估乳腺炎问题所使用的方法。与相关的无约束选择相比，使用对数SCC对总体效率有显著且可变的负面影响（根据参数为-8.9%至-36%）。与无约束选择相比，同时使用对数SCC和淘汰率对总体效率有中等影响（-4.9%至-7.4%）。
