TITLE:
Association between growth rates, age at first calving and subsequent fertility, milk production and survival in Holstein-Friesian heifers
AUTHORS:
Jessica S. Cooke, Zhangrui Cheng, Nicola E. Bourne, D. Claire Wathes
KEYWORDS:
Age at First Calving; Heifer; Fertility; Milk Production; Longevity
JOURNAL NAME:
Open Journal of Animal Sciences,
Vol.3 No.1,
January
24,
2013
ABSTRACT: Age
at first calving (AFC) affects the profitability of dairy enterprises. This
study examined the relationships between AFC and subsequent fertility, milk
production and survival up to third calving in UK Holstein-Friesian heifers;
Study 1 comprised 134 consecutively born heifers from the same herd (AFC 764 ±
8 days) and Study 2 contained 445 heifers born on 17 farms (AFC 796 ± 6 days).
Growth rates and fertility during rearing were monitored and animals were subsequently
divided into four AFC groups for analysis: 30 months. The actual AFC reflected both growth rate and heifer
fertility, with later calving heifers already lighter by 6 months of age. The proportion conceiving to first service was highest (93% and 84% for Studies 1 and 2, respectively) for the youngest AFC group.
Fertility in the first lactation was best in cows calving at 23 - 25 months and worst in the oldest AFC group.
Milk production parameters in the first and second lactations were broadly
similar between AFC groups but significantly more heifers with an AFC 44% of their days alive spent
in milk production compared with only 18% - 40% in cows calving at ≥26 months.
Hence cows with an AFC 0.75 kg/d
up to 15 months and good heifer fertility and resulted in the best subsequent
performance.