Laben R L, Shanks R, Berger P J, Freeman A E
J Dairy Sci. 1982 Jun;65(6):1004-15. doi: 10.3168/jds.S0022-0302(82)82302-3.
Dairy Herd Improvement testing records of 201 dairy herds of sizes from under 100 to over 1000 cows and herd average milk yields from under 5,000 to over 10,000 kg were studied. Average days to first postpartum breeding tended to be less in herds of over 500 cows. Herds of 300 to 600 cows had highest production per cow. Herds with higher average yields averaged shorter intervals to first postpartum breeding and fewer days open. Days open included farrow cows arbitrarily assigned 305 days open. Number of breedings changed little as herd yield increased, but days open for highest producing herds averaged one estrous period shorter than for low producing herds, suggesting better detection of estrus. For the individual cow, high yield or associated factors have a small but real antagonistic association with reproductive efficiency. Days to first breeding, to last breeding, and days open increased .27, .80, and .61, and number of breedings increased .014 for each 100 kg increase in 180-day yield of fat-corrected milk. The record averages of high-producing herds indicate this antagonism may be overshawdowed by good management; effective estrus detection probably is a major factor.
对201个奶牛群的奶牛群改良测试记录进行了研究，这些牛群规模从不到100头到超过1000头不等，牛群平均产奶量从不到5000公斤到超过10000公斤。产犊后首次配种的平均天数在奶牛超过500头的牛群中往往较少。300至600头奶牛的牛群每头牛的产量最高。平均产量较高的牛群产后首次配种的间隔时间较短，空怀天数较少。空怀天数包括任意分配305天空怀的经产母牛。随着牛群产量的增加，配种次数变化不大，但高产牛群的空怀天数平均比低产牛群短一个发情期，这表明发情检测更好。对于个体奶牛，高产或相关因素与繁殖效率存在微小但真实的拮抗关系。每100公斤校正乳脂的180天产量增加，首次配种天数、最后一次配种天数和空怀天数分别增加0.27天、0.80天和0.61天，配种次数增加0.014次。高产牛群的记录平均值表明，这种拮抗作用可能会被良好管理所掩盖；有效的发情检测可能是一个主要因素。
