@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}
}
