Phenotypic relationships between milk protein percentage and reproductive performance in three strains of Holstein Friesian cows in Ireland
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CitationYang, 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
AbstractThe 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.
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