Metabolic responses to glucose challenge in New Zealand and
overseas Holstein-Friesian dairy cows
L.M. CHAGAS, B.A. CLARK, F.M. RHODES, D. BLACHE, E.S. KOLVER AND
G.A. VERKERK
Dexcel Limited, Private Bag 3221, Hamilton, New Zealand
E-Mail:
NZSAP 2003 Abstract No. 9
Proceedings of the New Zealand Society of Animal Production
63: 31-34
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.
Keywords: NZSAPAB;
dairy cows; genotype; diet; glucose challenge; postpartum;
metabolites
Last Updated 8/07/2004
