Growth hormone treatment changes individual plasma and mammary tissue amino acid concentrations and variance.

<p>Absolute concentrations (heatmap) and statistical significance of differences in the mean concentration¹ and variance² of amino acids in the plasma (A) and the mammary tissue (B) of cows treated with growth hormone (GH) or saline solution (Control) (<i>n</i> = 4 per treatment). Absolute concentration of plasma lysine was decreased in GH-treated cows with a similar trend observed for arginine, methionine and tyrosine (A). Absolute concentrations of other individual plasma AA were unaffected (A). The absolute concentration of the arginine was decreased in mammary tissue of GH-treated cows compared to controls (B). A significant increase in the absolute concentration of glutamine, serine and glycine was also observed in the mammary tissue of GH-treated cows (B). Reduced variance in the concentration of plasma AAs methionine, tyrosine, alanine, ornithine and valine with a similar trend for leucine and asparagine (A) and mammary tissue AAs glutamine, lysine and valine with a similar trend for alanine, asparagine, phenylalanine, tyrosine, arginine, histidine, leucine and isoleucine (B) was observed in GH-treated cows. Differences were assessed using the TTEST procedure in SAS 9.1 (SAS Institute Inc., Cary, North Carolina, USA) which included the fixed effects of animal, treatment and amino acid (individual or pool). *: <i>P</i> ≤ 0.05; and trend: †: <i>P</i> ≤ 0.15.