@conference {41794,
	title = {Association between milk protein concentration and preceding reproductive performance in Holstein-Friesian heifers and cows in Australia},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {68},
	year = {2008},
	month = {Jan},
	pages = {69-72},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Brisbane, Australia},
	abstract = {Milk protein concentration (MP\%) has been associated with reproductive performance amongst parous dairy cows. This study aimed to assess whether early lactation MP\% of primiparous cows was associated with prior reproductive performance, and to compare the strength of the association between MP\% and previous reproductive performance in nulliparous heifers with that in multiparous cows. Primiparous (n = 918 in 35 herds) and multiparous (n = 4,242 in 64 herds) Holstein-Friesian cows with milk production/composition records and sire genetic information in seasonally calving herds were selected from the InCalf database. The date for each herd{\textquoteright}s planned start of calving (PSC) was calculated as being 282 d after the date breeding started. The interval between a herd{\textquoteright}s PSC date and each cow{\textquoteright}s actual calving date (PSC - CI) will therefore reflect time to conception during the previous breeding period. Higher MP\% was positively associated with shorter PSC-CI in both primiparous and multiparous cows. Across the range of cows that had a MP\% that was {\textpm} 0.5\% of the herd{\textquoteright}s mean MP\%, those with the lowest MP\% had an average PSC-CI that was either 13 d or from 28 to 32 d later in primiparous or multiparous cows, respectively. These associations were likely due to biological determinants present before and during the cow{\textquoteright}s breeding period that were associated with both reproductive performance and subsequent MP\%. Since these determinants affected the reproductive performance of non-lactating heifers, some of the associations with MP\% were not related to lactation-specific factors even though these same factors may have increased the effect of low MP\% on the reproductive performance of the multiparous Holstein-Friesian cows. },
	issn = {1176-5283},
	author = {Fahey J and Morton JM and Macmillan KL}
}
@conference {41411,
	title = {Relationships between milk protein percentage and reproductive performance in Australian dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {63},
	year = {2003},
	month = {Jan},
	pages = {82-86},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Queenstown},
	abstract = {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). Three week 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. },
	issn = {1176-5283},
	author = {Fahey J and Morton J and Macmillan KL}
}
