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Blood plasma concentrations of metabolic hormones and glucose during extended lactation in grazing cows or cows fed a total mixed ration

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journal contribution
posted on 2010-12-01, 00:00 authored by K Delany, K Macmillan, C Grainger, P Thomson, D Blache, Kevin Nicholas, M Auldist
An experiment was conducted to measure the effect of diet on circulating concentrations of metabolic hormones and metabolites in cows undergoing extended lactations. Two groups of 6 Holstein-Friesian cows managed for lactations of 670 d were used in the experiment. One group was fully fed on a total mixed ration (TMR), whereas the other group grazed fresh pasture supplemented with grain (P+G). On 7 occasions between 332 and 612 d in milk, concentrations of metabolic hormones and glucose were measured in the blood plasma of each cow. Cows fed TMR gained more weight and body condition than P+G cows, but did not produce more milk during the study period. Only 3 of the TMR cows continued to lactate until 612 d in milk compared with all 6 of the P+G cows. Blood plasma from cows fed TMR had higher concentrations of glucose, insulin, glucagon, insulin-like growth factor 1, and leptin, but lower concentrations of growth hormone, than that from P+G cows. These changes were consistent with the preferential deposition of energy into adipose tissue at the expense of milk production and presumably were induced by a diet that provided precursors for gluconeogenesis that were in excess of the requirements for maintenance and prevailing milk production. The mechanism responsible for some TMR cows putting on excess weight and reducing or ceasing milk production is uncertain, but this observation has important implications for the nutritional management of cows in extended lactation programs.

History

Journal

Journal of dairy science

Volume

93

Pagination

5913 - 5920

Location

New York, N.Y.

Open access

  • Yes

ISSN

1525-3198

eISSN

0022-0302

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2010, American Dairy Science association

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