@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 {41671,
	title = {Variation in yields of milk and milk solids in Holstein cows induced to calve prematurely},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {66},
	year = {2006},
	month = {Jan},
	pages = {344-349},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Napier},
	abstract = {Milk production was compared between multiparous Holstein cows that were induced to calve and herdmates that calved spontaneously at approximately the same time in 88 dairy herds from Victoria and Tasmania. Yield averages for each herd were calculated for induced and spontaneously calving cows for milk volume, milkfat and protein during the first 120 days of lactation and for 305 days. Associations between induced and spontaneously calving groups for 305-day yields were described using linear equations. Slopes ranged from 0.82 (for milk yield) to 0.87 (for protein yield) and R2 values ranged from 0.84 to 0.88 (P<0.001). The average reduction in milk yield over the 88 herds was 366 litres (7\%). The estimated milk yield reduction for induced groups in herds where spontaneously calving contemporaries averaged only 3500 litres per 305 days was 40 litres (1.1\%) compared to an average estimated reduction of 915 litres (11\%) in herds averaging 8500 litres. Similar proportional reductions were calculated for 305-day yields of milkfat and protein. Collectively these results show that yield reductions following induced premature parturition are substantially higher in absolute as well as proportional terms in herds with higher milk yields. },
	issn = {1176-5283},
	author = {Jaques SA and Macmillan KL and Anderson GA and Morton JM}
}
