Thorpe W, Morris C A, Kang'ethe P
International Livestock Centre for Africa, Mombasa, Kenya.
J Dairy Sci. 1994 Aug;77(8):2415-27. doi: 10.3168/jds.S0022-0302(94)77184-8.
Records from 1577 cows born from 1973 to 1983 on a ranch in lowland Kenya were analyzed for age at first calving, lactation length, lactational milk yield, calving interval, annual milk yield, and, for cows born from 1973 to 1979, number of calvings, productive lifetime in the herd, and lifetime milk yield. Partial lifetime yield (< or = 4 lactations) was studied for all cows. Rotational crosses of Ayrshire and Sahiwal, the crosses between them (interbreds), and the crosses sired by Brown Swiss from the rotational crosses were compared. The Ayrshire-sired rotational crosses yielded 4.8% more milk during a 19-d longer lactation and with a calving interval that was 14 d longer than those sired by Sahiwal. Milk yield for completed lactations of interbred cows was 4.5% less, and milk yield of Brown Swiss crosses was 9.5% more, than the average of the rotational crosses. Lifetime milk yields were 48% greater for the rotational crosses sired by Ayrshire than for those sired by Sahiwal. Interbreds yielded 34% less than the average of the rotational crosses. Over partial lifetimes, the rotational crosses sired by Ayrshire yielded 45% more milk than those sired by Sahiwal; the interbreds and the crosses sired by Brown Swiss yielded 34% less and 62% more milk, respectively, than the mean of the rotational crosses.
对肯尼亚低地一个牧场1973年至1983年间出生的1577头母牛的记录进行了分析，内容包括首次产犊年龄、泌乳期长度、泌乳期产奶量、产犊间隔、年奶产量，对于1973年至1979年出生的母牛，还包括产犊次数、在牛群中的生产寿命和终生奶产量。研究了所有母牛的部分终生产量（≤4个泌乳期）。比较了艾尔夏牛与萨希瓦尔牛的轮回杂交后代、它们之间的杂交种（杂种）以及轮回杂交中由瑞士褐牛所生的杂交后代。由艾尔夏牛所生的轮回杂交后代在泌乳期长19天的情况下产奶量高出4.8%，且产犊间隔比由萨希瓦尔牛所生的后代长14天。杂种母牛完整泌乳期的产奶量比轮回杂交后代的平均产奶量少4.5%，而瑞士褐牛杂交后代的产奶量比轮回杂交后代的平均产奶量多9.5%。由艾尔夏牛所生的轮回杂交后代的终生奶产量比萨希瓦尔牛所生的后代高48%。杂种的产量比轮回杂交后代的平均产量少34%。在部分终生期间，由艾尔夏牛所生的轮回杂交后代的产奶量比萨希瓦尔牛所生的后代多45%；杂种和瑞士褐牛所生的杂交后代的产奶量分别比轮回杂交后代的平均值少34%和多62%。
