Morris S T, Morel P C H, Kenyon P R
Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
N Z Vet J. 2006 Apr;54(2):96-100. doi: 10.1080/00480169.2006.36619.
To examine of the influence of liveweight (LW), condition (CS) and age of dam on inter-calving interval (ICI), date of calving, days from joining to calving, and birth and weaning weights of calves.
LW and CS were measured in a herd of mixed-aged (3-8 years) Hereford x Friesian beef cows on four occasions, annually, over a 3-year period from joining (the date bulls were introduced into the herd at the start of a restricted breeding season) in November 2000 to weaning in March 2004. The four dates of weighing and condition-scoring were joining (November), weaning (March), winter (June), and pre-calving (August). Calves were tagged, identified to their dam, and weighed within 24 h of birth, and at weaning. Date of calving, ICI and days from joining to calving were determined.
The CS and LW of cows varied between years. LW increased in cows up to 6 years of age. Three-year-old cows had a longer ICI than older cows. Change in CS and LW from winter to pre-calving and pre-calving to joining were negatively correlated with ICI for younger cows but not for cows > or = 5 years (CS) and 6-8 years (LW) old. No difference in CS or LW precalving was evident between cows that subsequently became pregnant compared with non-pregnant cows, although cows that became pregnant gained more condition from pre-calving to joining than non-pregnant cows. Pregnant cows were heavier and had higher CS at joining than non-pregnant cows.
Young cows, up to second-mating as 3-year-olds, would benefit from separate nutritional management from older cows, to ensure ICI and days to conception are kept at targeted levels. In addition, increasing CS from pre-calving to joining and higher LW and CS at joining resulted in higher pregnancy rates.
研究母牛体重（LW）、体况（CS）和年龄对产犊间隔（ICI）、产犊日期、配种至产犊天数以及犊牛出生体重和断奶体重的影响。
在一群年龄混合（3 - 8岁）的赫里福德×弗里斯兰肉牛母牛中，于2000年11月配种（在限定繁殖季节开始时将公牛引入牛群的日期）至2004年3月断奶的3年期间，每年四次测量LW和CS。四次称重和体况评分的日期分别为配种期（11月）、断奶期（3月）、冬季（6月）和产犊前期（8月）。犊牛佩戴标签，确定其母亲，并在出生后24小时内及断奶时称重。确定产犊日期、ICI和配种至产犊天数。
母牛的CS和LW随年份变化。6岁以下母牛的LW增加。3岁母牛的ICI比年龄较大的母牛长。对于较年轻的母牛，从冬季到产犊前期以及从产犊前期到配种期CS和LW的变化与ICI呈负相关，但对于5岁及以上（CS）和6 - 8岁（LW）的母牛则不然。与未怀孕的母牛相比，随后怀孕的母牛在产犊前期的CS或LW没有明显差异，不过怀孕母牛从产犊前期到配种期比未怀孕母牛增加了更多体况。怀孕母牛在配种时比未怀孕母牛更重且CS更高。
3岁进行第二次配种的年轻母牛，将受益于与年龄较大母牛分开的营养管理，以确保ICI和受孕天数保持在目标水平。此外，从产犊前期到配种期增加CS以及在配种时提高LW和CS会导致更高的怀孕率。
