Abstract

Milk production involves a coordinated metabolic response from multiple tissues. Administration of growth hormone (GH) to lactating cows provides an endocrine signal that redirects nutrients towards milk production. Hepatic responses to GH define the nutrient supply to peripheral organs both directly and indirectly, through processes such as gluconeogenesis and endocrine modulation. However, the mechanisms controlling these processes in the liver itself have not been completely elucidated. Our objective was to evaluate the effect of GH on gene expression in the liver of lactating dairy cows. Using a 22,690 expressed sequence tags (EST) bovine cDNA microarrays, we examined differences in liver mRNA transcript profiles between four cows treated with a slow-release formulation of GH and four control cows treated with saline solution. We identified 38 unique transcripts in liver that met the criteria of having expression changes greater than +/- 1.2 fold and false discovery rates <0.05. Of these genes affected by GH, 29 were down-regulated and nine were up-regulated. The pathways most affected by GH were carbohydrate and lipid metabolism, molecule transport and small molecule biochemistry. This preliminary study provides further insights into the molecular changes involved in the effects of GH on liver gene expression in the lactating dairy cow.

D, Pacheco, K Nones, Q Sciascia, and SA McCoard

Proceedings of the New Zealand Society of Animal Production, Volume 70, Palmerston North, 33-38, 2010