Impact of age at calving on lactation and reproduction performance at the first-parity holsteins

Abstract

The aim of this study was to determine
the impact of age at first calving (AFC) on lactation
and reproduction performance in dairy cows. Thirtytwo
first-parity Holsteins were distributed in two
groups by AFC: 16 first-parity females were named
as “Younger”, with AFC lower than 700 days, and 16 were classified as “Older”, with AFC above
700 days. Lactation and reproduction data were
analyzed using GLM procedure from SAS. Firstlactation
cows that calved before 700 days of age
displayead lower (P<0,05) milk yields (9,900 vs.
10,874 kg), lower (P<0,05) 3,5% fat-corrected milk
yields (10,341 vs. 11,618 kg), lower (P<0,05) fat
yields (373 vs. 425 kg), and lower (P<0,05) protein
yields (279 vs. 307 kg) than first-parity Holsteins
that calved after 700 days of age. There were no
differences between the two groups of AFC for
fat and protein contents: 3,80% vs. 3,96% fat and
2,81% vs. 2,81% protein, respectively for Younger
and Older females. Reproduction results showed
that first-parity cows that calved earlier, before 23
months of age, had better (P<0,05) reproduction
performance than primipara cows that calved later,
after 23 months of age: lower days in milk at first
estrous (48,9 vs. 70,4 days), lower days open (69,8
vs. 110,2 days), and lower calving interval (359,2
vs. 390,1 days).