Relationships between milk protein percentage and reproductive
performance in Australian dairy cows
J. FAHEY, J. MORTON AND K.L. MACMILLAN
Department of Veterinary Science, Victorian Institute of Animal
Science, University of Melbourne, 600 Sneydes Road, Werribee, Victoria
3030, Australia.
E-Mail:
NZSAP 2003 Abstract No. 21
Proceedings of the New Zealand Society of Animal Production
63: 82-86
The InCalf Project included a large, prospective, observational
field study that described the reproductive performance of 29,462 dairy
cows in 168 herds throughout Australia. Milk protein percentage was
identified as one of six factors associated with herd reproductive
performance. In this further study, a subset of the original database
was used and then refined to only include Holstein cows with between one
and five milk production records during the first 120 days of lactation
in seasonal-calving herds which carried out artificial insemination (AI)
for at least the first six weeks of the mating period. This subset then
comprised 8,795 cows in 66 herds. Cows in the subset were divided into
four quartiles based on early lactation milk protein percentage and five
intervals from calving to mating start date (MSD). Threeweek submission
rate and six-week in-calf rate were lower (P<0.001) and the 21-week
not-in-calf rate was higher (P<0.001) for cows in the lowest compared
to the highest quartiles for milk protein percent. The association
between milk protein percentage and reproductive performance was driven
mainly by the incidence of non-cycling cows with consequent effects on
submission rate in the first three weeks of AI as well as in the second
three weeks. In conclusion, late calving cows with low milk protein
percentage were at the greatest risk of not being submitted for AI and
remaining not in-calf at the end of a relatively long mating period of
21 weeks.
Keywords: NZSAPAB;
milk protein percentage; fertility; reproduction;
Holstein-Friesian; dairy cow
Last Updated 8/07/2004
