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Phenotypic relationships between milk protein percentage and reproductive performance in three strains of Holstein Friesian cows in Ireland
Yang, L Lopez-Villalobos, N Berry, Donagh Parkinson, T
Yang, L
Lopez-Villalobos, N
Berry, Donagh
Parkinson, T
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2021-04-11
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Yang, L., Lopez-Villalobos, N. Berry, D. P., Parkinson, T. Phenotypic relationships between milk protein percentage and reproductive performance in three strains of Holstein Friesian cows in Ireland. Proceedings of the New Zealand Society of Animal Production 2010 Vol.70 pp.29-32
Abstract
The relationship between milk protein percentage and fertility in seasonal calving, dairy cattle in Ireland
was quantified using a total of 584 lactation records, collected over a five-year period from experiments
comparing three strains of Holstein-Friesian cows under three different feeding systems. Logistic regression
analyses showed that increased protein percentage during early lactation was positively associated with the
probability of a cow becoming pregnant to its first service (P <0.05). Similarly, protein percentage during the
lactation had a positive (P <0.01) association with overall pregnancy rate. The results suggest that negative
energy balance in early lactation or during the whole lactation causes a shortage of glucose to the udder, this
restricts the synthesis of milk protein in the udder and causes a lower milk protein percentage. During negative
energy balance there is also a concurrent reduction of IGF-І, LH and oestradiol secretion, which consequently
delay ovarian follicular development, and hence impairs reproductive performance. In conclusion, cows with
higher milk protein percentage during early lactation have a greater likelihood of becoming pregnant earlier in
the breeding season, and have a higher conception rate.