Production and Sectors Department, Walloon Agricultural Research Centre, Rue de Liroux 8, 5030 Gembloux, Belgium.
Animal. 2013 Apr;7(4):665-72. doi: 10.1017/S1751731112001577. Epub 2012 Aug 10.
The effects of first calving (FC) in Holstein heifers on their first lactation, second lactation and lifetime milk production were examined from an initial database of 459 743 animals that first calved between 1 January 1990 and 31 July 2010 in Wallonia, Belgium. The FC age class (18 to 22, 22 to 26, 26 to 30, 30 to 34, 34 to 38 and 38 to 42 months), the FC season and FC year class (1990 to 1994, 1995 to 1999, 2000 to 2004 and 2005 to 2010) were considered when analysing the first and second lactation data. Lifetime data were similarly analysed, but did not include animals that calved after 2005 because many of them were still lactating. Only 24% of animals had their FC before 26 months of age. Animals that first calved between 22 and 26 months of age had more lactations and productive days during their life. They also had higher first and second lactation milk production and lifetime milk production. Summer or autumn FC improved first lactation, second lactation and lifetime milk production, as well as production per day of lactation, compared with winter or spring FC. Compared with animals that calved for the first time in 1990 to 1994, animals with a FC in 2000 to 2004 had a longer calving interval (0.5 months), fewer lactations per animal (-0.6) and fewer days in their lifetime lactation (a reduction of 144 days). As a result, the animals' lifetime production did not increase between 1990 to 1994 and 2000 to 2004, although milk production per day of lactation (22.85 v. 20.49 l/day) and per day of life (11.49 v. 10.78 l/day) improved. Milk fat content was lower in 2000 to 2004 than in 1990 to 1994, but protein content remained relatively constant, probably because of the cows' higher production level and increased dietary concentrate supplementation.
从最初的数据库中检查了荷斯坦小母牛首次产犊（FC）对其首次泌乳、第二次泌乳和终生产奶的影响，该数据库包含了 1990 年 1 月 1 日至 2010 年 7 月 31 日期间在比利时瓦隆首次产犊的 459743 头动物。分析首次和第二次泌乳数据时，考虑了 FC 年龄组（18-22、22-26、26-30、30-34、34-38 和 38-42 个月）、FC 季节和 FC 年份组（1990-1994、1995-1999、2000-2004 和 2005-2010）。同样对终生数据进行了分析，但不包括 2005 年后产犊的动物，因为它们中的许多仍在泌乳。只有 24%的动物在 26 个月龄之前首次产犊。在 22-26 月龄首次产犊的动物在其生命中具有更多的泌乳和产奶天数。它们还具有更高的首次和第二次泌乳产奶量和终生产奶量。与冬季或春季产犊相比，夏季或秋季产犊提高了首次泌乳、第二次泌乳和终生产奶量，以及泌乳天数的产奶量。与 1990-1994 年首次产犊的动物相比，2000-2004 年首次产犊的动物产犊间隔更长（0.5 个月），每头动物的泌乳次数减少（0.6 次），终生泌乳天数减少（减少 144 天）。因此，尽管泌乳天数（22.85 升/天对 20.49 升/天）和生命天数（11.49 升/天对 10.78 升/天）的产奶量有所提高，但动物的终生产量在 1990-1994 年和 2000-2004 年之间并未增加。牛奶中的脂肪含量在 2000-2004 年比 1990-1994 年低，但蛋白质含量相对稳定，可能是因为奶牛的产量水平更高，饲料浓缩物的补充量增加。
