Ghrelin is an endogenous ligand of the growth hormone secretagogue receptor, and a potent orexigenic agent in human and rodent studies. We hypothesized that ghrelin may play a role in the reduced grazing time in dairy cows receiving supplementary feeds. Fiftyeight Holstein-Friesian (HF) dairy cows of New Zealand (NZ; n = 28) and North American (NA; n = 30) ancestry were provided with unrestricted access to pasture and randomly allocated at calving to either 0, 3, or 6 kg of dry matter concentrates in a 2 × 3 factorial arrangement. Concentrates were offered in equal amounts at each milking. In peak lactation (75 and 79 ± 19.7 d in milk), blood was sampled from all cows prior to the a.m. milking (i.e., baseline) and following 2 h of unrestricted access to fresh pasture after the a.m. milking on 2 consecutive weeks. Daily milk yield and fat, protein, and lactose concentrations were measured on the day of blood sampling. North American cows produced more milk and consumed numerically more pasture than did NZ cows, and NA cows had elevated plasma ghrelin concentrations pre- and postfeeding. A negative association between dry matter intake and postprandial ghrelin concentrations indicated that other controlling factors may be involved. Circulating ghrelin concentrations before feeding were not affected by concentrate supplementation, but increasing supplementation was associated with a linear decline in pasture intake and postprandial ghrelin concentrations. This negative association between concentrate supplementation and plasma ghrelin concentrations offers a potential neuroendocrine basis for the reduced pasture intake when supplements are offered to cows in grazing systems. © American Dairy Science Association, 2007.

Item Type:	Refereed Article
Research Division:	Agricultural and Veterinary Sciences
Research Group:	Animal Production
Research Field:	Animal Nutrition
Objective Division:	Animal Production and Animal Primary Products
Objective Group:	Livestock Raising
Objective Field:	Dairy Cattle
UTAS Author:	Roche, JR (Dr John Roche)
ID Code:	41281
Year Published:	2007
Web of Science® Times Cited:	31
Deposited By:	Agricultural Science
Deposited On:	2007-08-01
Last Modified:	2009-11-03
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