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Trends in the reproductive performance of Holstein dairy cows in Iran

机译：伊朗荷斯坦奶牛繁殖性能的趋势

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The study was undertaken to determine the trends in the reproductive performance of Holstein dairy cows in Iran during 1994 to 2008. Reproductive performance data for 528,034 lactations of 246,132 cows in 1,822 Holstein dairy herds of Iran were used. The potential effect of calving season, herd, parity, calving year, as well as herd size and 305-day milk production on reproductive performance traits was investigated using multiple regression models. The least squares means of age at first calving decreased by 3.1 (+or-0.06) days per year from 806.5 (+or-96.3) days in 1994 to 788 (+or-89.9) days in 2008. The least squares means of calving interval increased 1.02 (+or-0.03) days per year from 394.1 (+or-65) days in 1994 to 413.2 (+or-81) days in 2008. Greater 305-day milk production was associated with an average increase of 6.55 (+or-0.08) days in calving interval per 1,000-kg increase in milk yield. Larger herd size was associated with an average decrease of 0.22 (+or-0.02) days in calving interval per 50 cows per herd. The mean number of days dry was 88.6 (+or-51.3) days and increased by 0.82 (+or-0.02) days per year. In conclusion, reproductive performance in Holstein dairy herds has generally decreased, whereas herd size and milk production have increased over time. Producers may make significant improvements in herd reproduction by reviewing management strategies including the sire selection, reproductive management, inseminator training and techniques, and improved estrous detection. Moreover, it may be advisable for the fertility traits to be included in the genetic selection indices to reduce the rate of reproductive decline.Digital Object Identifier http://dx.doi.org/10.1007/s11250-012-0170-9
机译：该研究旨在确定1994年至2008年期间伊朗荷斯坦奶牛繁殖性能的趋势。使用了伊朗1,822个荷斯坦奶牛场528,034头泌乳246,132头母牛的生殖性能数据。使用多重回归模型研究了产犊季节，牛群，胎次，产犊年以及牛群大小和305天产奶量对生殖性能特征的潜在影响。第一次产犊的最小平方均值从1994年的806.5（+或-96.3）天减少到2008年的788（+或-89.9）天，每年减少3.1（+或-0.06）天。间隔从1994年的394.1（+或-65）天每年增加1.02（+或-0.03）天，到2008年为413.2（+或-81）天。305天的奶产量增加与平均增加6.55（每增加1000公斤产奶量，产犊间隔增加+或-0.08）天。较大的牛群与每50头牛的产犊间隔平均减少0.22天（+或-0.02）相关。干燥的平均天数为88.6（+或-51.3）天，并且每年增加0.82（+或-0.02）天。总之，随着时间的推移，荷斯坦奶牛场的生殖性能普遍下降，而牛群的大小和产奶量却有所增加。生产者可以通过回顾管理策略，包括选种，繁殖管理，授精者培训和技术，以及改善发情检测，来显着改善畜群繁殖。此外，建议将生育力性状纳入遗传选择指数以减少生殖衰退的速率。数字对象标识符http://dx.doi.org/10.1007/s11250-012-0170-9

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