荷斯坦青年牛初次配种妊娠月龄对头胎和二胎产奶量和繁殖性能的影响

旨在研究母牛初次配种妊娠月龄（age at first pregnancy，AFP）对其泌乳性能和主要繁殖性能的影响。本研究以我国北方地区2个规模化奶牛场13 927头荷斯坦母牛（A牧场8 091头，B牧场5 836头）的生产数据为基础，统计了母牛AFP、头胎和二胎的产奶量、产后首次发情时间、首次配种时间和首次受孕时间，然后将母牛根据AFP的早晚（12~19月龄）分为8组，对各试验组母牛的头胎和二胎产奶量和主要繁殖性能的数据进行比较分析。结果表明：1）2个规模化奶牛场荷斯坦青年牛AFP以13和14月龄为主（总占比70.1%）；2）AFP可显著影响荷斯坦青年牛头胎和二胎的305 d产奶量（P<0.05），其中AFP为14月龄时A牧场头胎和二胎305 d产奶量均最高，分别为15 102和15 534 kg；3）AFP可显著影响荷斯坦青年牛头胎和二胎产后首次发情时间和受孕时间（P<0.05），AFP为14月龄时头胎产后首次发情和受孕情况最优；4）对于产后首配时间，除A牧场头胎AFP为16月龄时产后首次配种时间显著高于AFP为17月龄时（P<0.05）外，其余各组间均无显著性差异（P ≥ 0.05），并且各组间配种时间相差≤ 5 d；5）通过对A牧场在场牛（2 703头）与淘汰牛（660头）的AFP记录数据分析发现，在场牛的AFP为14.52月龄，显著高于淘汰牛的AFP（P<0.05）。因此，在北方地区现有的生产管理水平下，14月龄可能是荷斯坦青年牛最适宜的初次配种妊娠月龄，这对我国规模化奶牛场选择荷斯坦青年牛适宜的初次配种月龄具有一定参考价值。

Effect of Age at First Pregnancy on Milk Production and Reproductive Performance During the First 2 Lactations in Holstein Dairy Cattle

This study aimed to analyze the effects of age at first pregnancy (AFP) on milk yield and reproductive performance of cows. In this study, production data of 13 927 Holstein dairy cows from two large-scale dairy cow herds (A herd 8 091,B herd 5 836) in northern China were collected. The age at first pregnancy (AFP), milk production, post-partum first estrus time during the first 2 lactations, first 2 mating time and first conception time during the first 2 lactations were detected. The cows were divided into 8 groups according to the AFP(12-19-month-old).The milk yield and main reproductive performance during the first 2 lactation of cows in different groups were compared and analyzed. The results showed that:1) The AFP of Holstein heifers in two large-scale farms were mainly in 13- and 14-month-old (accounting for 70.1% of the total); 2) AFP could significantly affect the 305 d milk production of Holstein dairy cows in the first 2 lactations (P<0.05), the highest 305 d milk production for the first 2 lactation (15 102 kg vs 15 534 kg) was obtained on 14-month-old for AFP in A herd; 3) AFP could significantly affect the post-partum first estrus time and first conception time of Holstein dairy cows in the first 2 lactation (P<0.05), the optimal post-partum first estrus time and first conception time for the first lactation was obtained on 14-month-old for AFP; 4)The post-partum first mating time of cows with AFP at 16-month-old in A farm was significantly higher than that of cows with AFP at 17-month-old for the first lactation (P<0.05), there was no significant difference among the other groups (P ≥ 0.05), and the difference in mating time among the groups was less than 5 days; 5) Based on the analysis of the AFP records of the cattle in the farm (2 703 heads) and the culling cattle (660 heads) in A farm, it was found that the AFP of the cattle in the farm was 14.52-month-old, which is significantly higher than the AFP of the culling cattle (P<0.05). In the northern region, under the current production management level, 14-month-old may be the most suitable age at first pregnancy for Holstein heifers, which has certain reference value for the age at first pregnancy for Holstein heifers in large-scale dairy farms in China.