Aspects of Heifer Rearing

Brickell, J S and McGowan, M M and Wathes, D C (2008) Aspects of Heifer Rearing. In: UNSPECIFIED.

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Abstract

Minimal losses, optimal growth rates and excellent fertility management are key factors of a good dairy heifer rearing system. This study determined the mortality, growth and fertility of Holstein-Friesian heifers on 19 UK dairy farms, and examined the relationships between growth parameters and concentrations of insulin-like growth factor-I (IGF-I), with each of these 3 key areas. A cohort of 506 heifer calves was recruited at I month and monitored through to first calving. Size parameters (body weight, heart girth, height at withers and crown-rump length) and concentrations of IGF-I were measured in each calf at approximately 1 and 6 months, and the average daily change in each size parameter was calculated. On average 8% of male and female calves were born dead, or died within 24 hours of life, and approximately 15% of heifer calves born alive failed to reach first calving. The mean daily weight gain up to 6 months of life was 0.77 +/- 0.01 kg/day, ranging considerably between individual calves across farms from 0.23 to 1.25 kg/day. Increased body size and IGF-I concentration at I month was associated with a reduced risk of mortality, and improved growth rates during the first 6 months of life. Mean age at first calving was 26 +/- 0.2 months; increased pre-pubertal weight gain was significantly associated with a reduced age at first calving. This study has shown that a large number of potential replacement heifers born on UK farms fail to reach their first lactation, and for those that survive, weight gain during the pre-pubertal period is an important factor influencing the length of the non-productive period.