Allaire F R, Gibson J P
Department of Dairy Science, Ohio State University, Columbus.
J Dairy Sci. 1992 May;75(5):1349-56. doi: 10.3168/jds.S0022-0302(92)77886-2.
Cow herd life adjusted for lactational milk production was investigated as a genetic trait in the breeding objective. Under a simple model, the relative economic weight of milk to adjusted herd life on a per genetic standard deviation basis was equal to CVY/dCVL where CVY and CVL are the genetic coefficients of variation of milk production and adjusted herd life, respectively, and d is the depreciation per year per cow divided by the total fixed costs per year per cow. The relative economic value of milk to adjusted herd life at the prices and parameters for North America was about 3.2. An increase of 100-kg milk was equivalent to 2.2 mo of adjusted herd life. Three to 7% lower economic gain is expected when only improved milk production is sought compared with a breeding objective that included both production and adjusted herd life for relative value changed +/- 20%. A favorable economic gain to cost ratio probably exists for herd life used as a genetic trait to supplement milk in the breeding objective. Cow survival records are inexpensive, and herd life evaluations from such records may not extend the generation interval when such an evaluation is used in bull sire selection.
在育种目标中，将经泌乳产奶量调整后的牛群寿命作为一个遗传性状进行了研究。在一个简单模型下，以每个遗传标准差为基础，牛奶相对于调整后牛群寿命的相对经济权重等于CVY/dCVL，其中CVY和CVL分别是产奶量和调整后牛群寿命的遗传变异系数，d是每头奶牛每年的折旧除以每头奶牛每年的总固定成本。在北美价格和参数条件下，牛奶相对于调整后牛群寿命的相对经济价值约为3.2。产奶量增加100千克相当于调整后牛群寿命延长2.2个月。与同时包含产奶量和调整后牛群寿命的育种目标相比，当仅追求提高产奶量时，预期经济增益会降低3%至7%，因为相对价值变化了+/-20%。将牛群寿命用作遗传性状以补充育种目标中的产奶量，可能存在有利的经济增益成本比。奶牛生存记录成本低廉，并且当在种公牛选择中使用此类记录进行牛群寿命评估时，可能不会延长世代间隔。
