@conference {41989,
	title = {Restricted postpartum feeding in grazing dairy heifers decreases milk production but does not lengthen oestrous interval},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {67},
	year = {2007},
	month = {Jan},
	pages = {255-260},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Wanaka},
	abstract = {The aim of this study was to determine the effects of pasture allowance postpartum on the initiation of ovarian activity, metabolite and hormonal secretion, and milk production. After calving, thirty six HolsteinFriesian heifers (BCS 5.0) received either unrestricted pasture allowance (UNR; n=18) or restricted (RES; 73\% dry matter intake of the unrestricted group;n=18) pasture allowance. The LW was lower (P < 0.05) for the RES group than the UNR group. Body condition score of all heifers decreased after calving in both groups. The mean time to ovulation was similar for UNR 50.0 and RES 50.3 sed. 8.2 days after individual calving date. The daily average from week 2 for milksolids, protein and lactose yield was lower (P < 0.05) in the RES group. Plasma concentrations of insulin were lower (P = 0.0085) in the RES group when compared to the UNR group. Glucose concentrations was lower (P = 0.016) in the RES group. Plasma concentration of NEFA was greater (P = 0.001) in the RES group. There was an interaction with treatment differences decreasing by week 11 and 12 for glucose (P =0.001) and NEFA (P =0.006). Plasma concentrations of leptin (P = 0.013) and IGF-I (P = 0.026) were lower in the RES. No differences, associated with postpartum nutrition, were found for plasma GH. Restricted feeding postpartum had no effect on days to first postpartum ovulation but decreased liveweight, milk production and affected some metabolic hormones during postpartum.},
	issn = {1176-5283},
	author = {Chagas LM and Gore PJS and MacDonald KA and Blache D}
}
@conference {41399,
	title = {Metabolic responses to glucose challenge in New Zealand and overseas Holstein-Friesian dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {63},
	year = {2003},
	month = {Jan},
	pages = {31-34},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Queenstown},
	abstract = {North American and Dutch Holstein-Friesian (HF) cattle have undergone genetic selection for increased milk production, however, at the same time, reproductive efficiency has decreased. Overseas HF also have greater propensity to mobilise body reserves during early lactation than New Zealand HF cows. It is possible that reproductive differences are a consequence of metabolic and endocrine differences between the strains. This trial was designed to investigate effects of genotype and diet on endocrine response to a challenge of intravenous glucose in HF cows. Twenty-five HF cows of New Zealand (NZ; n=13) and Overseas (OS; n=12) origin, were fed either pasture (Grass; n=12) or a total mixed ration (TMR; n=13) in a 2x2 factorial design. At two weeks postpartum, they were challenged with 300mg of glucose/kg live weight. Data were analysed for effects of genotype and diet. Following glucose challenge, the NZ TMR cows had higher plasma insulin concentrations than the NZ Grass, resulting in a significant interaction between diet and genotype in the area under the response curve; but the OS groups had similar patterns. Mean plasma leptin concentration was higher in NZ TMR than in NZ Grass, OS TMR or OS Grass. Plasma concentrations of glucose and IGF-I were not affected by genotype or feed regime. These results demonstrated metabolic differences between the strains and also diets. A better understanding of the genetic and nutritional basis of hormonal regulation of nutrient partitioning will be important to develop nutritional strategies to meet the requirements of lactating cows with different genotypes, and to find ways to improve reproductive efficiency. },
	issn = {1176-5283},
	author = {Chagas LM and Clark BA and Rhodes FM and Blache D and Kolver ES and Verkerk GA}
}
