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Abstract

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.

Item Type:	Article
Authors/Creators:	Roche, JR and Sheahan, AJ and Chagas, LM and Berry, DP
Keywords:	ghrelin • Holstein-Friesian strain • pasture • concentrate supplementation
Journal or Publication Title:	Journal of Dairy Science
Publisher:	American Dairy Science Association
ISSN:	0022-0302
Item Statistics:	View statistics for this item

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