一项详细调查初产2岁肉用小母牛产犊性能及助产结果的研究。

Hickson R E, Anderson W J, Kenyon P R, Lopez-Villalobos N, Morris S T

Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.

N Z Vet J. 2012 Jan;60(1):35-41. doi: 10.1080/00480169.2011.633878.

AIM

To examine via a survey the management at calving of primiparous, 2-year-old beef heifers on selected beef cattle farms in New Zealand and to investigate the causes and outcomes of assisted calving of these heifers.

METHODS

An initial survey of beef cattle farmers identified that many beef breeding heifers were assisted at parturition in 2006. The outcome of assistance at parturition in the industry was not examined in that survey. A two-part questionnaire was sent to 204 respondents to the previous survey who had indicated a willingness to participate and had bred 15-month-old heifers in 2006. These respondents are unlikely to be a representative sample of all beef cattle farmers in New Zealand. A total of 127 responses were received to Part A, which encompassed mating and calving management and results and 107 responses were received to Part B, which addressed survival of calves and management of the replacement heifers.

RESULTS

A total of 6726 heifers were joined with bulls in the respondents' herds in 2006. The percentage of calves born to primiparous, 2-year-old heifers present at marking was 83 (95% CI = 80-86)% of heifers joined with a bull. Overall assistance percentage was 9.7 (95% CI = 7.6-11.9)%, and 30 (95% CI = 25-35)% of 376 calves assisted at birth for which fate was reported were stillborn. The predominant cause of assisted calving was feto-maternal disproportion, and 11 (95% CI = 7-16)% of assisted heifers had died by 4 weeks postpartum. The most common time to first graze heifers with the mature cow herd was between first calving and second mating. Eighty-five (95% CI = 58-100)% of heifers that calved at 2 years of age in 2006 calved again in 2007 and this was not affected by stage of integration into the mixed-aged cow herd. Failure to conceive at second mating was the predominant reason for heifer attrition: 3.8 (95% CI = 0-16)% were culled after being diagnosed non-pregnant and a further 2.3 (95% CI = 0-18)% were carried over as empty 3-year-old heifers.

CONCLUSIONS

The 85% retention of heifers as second-calving, 3-year-olds indicated that heifers were achieving adequate rebreeding rates after first calving. The survival of heifers and calves in the neonatal period could be increased by reducing the need for or improving the outcomes of assistance at parturition.

目的

通过一项调查研究新西兰部分肉牛养殖场中初产的2岁肉用小母牛产犊时的管理情况，并探究这些小母牛助产的原因及结果。

方法

对肉牛养殖户的初步调查发现，2006年许多肉牛繁殖小母牛在分娩时得到了助产。该调查未研究该行业分娩助产的结果。向之前调查中的204名受访者发送了一份分为两部分的问卷，这些受访者表示愿意参与，且在2006年饲养了15月龄的小母牛。这些受访者不太可能是新西兰所有肉牛养殖户的代表性样本。共收到127份对A部分的回复，该部分涵盖配种和产犊管理及结果；收到107份对B部分的回复，该部分涉及犊牛存活情况及后备小母牛的管理。

结果

2006年受访者牛群中共有6726头小母牛与公牛配种。在标记时在场的初产2岁小母牛所产犊牛的比例为与公牛配种小母牛的83%（95%置信区间 = 80 - 86%）。总体助产比例为9.7%（95%置信区间 = 7.6 - 11.9%），在报告了命运的376头出生时得到助产的犊牛中，30%（95%置信区间 = 25 - 35%）为死产。助产的主要原因是胎儿与母体比例失调，11%（95%置信区间 = 7 - 16%）的助产小母牛在产后4周内死亡。小母牛首次与成年母牛群一起放牧的最常见时间是在第一次产犊和第二次配种之间。2006年2岁产犊的小母牛中，85%（95%置信区间 = 58 - 100%）在2007年再次产犊，这不受融入不同年龄母牛混合群阶段的影响。第二次配种未受孕是小母牛淘汰的主要原因：3.8%（95%置信区间 = 0 - 16%）在被诊断未怀孕后被淘汰，另有2.3%（95%置信区间 = 0 - 18%）作为空怀的3岁小母牛留存。