Effect of moderate alterations of dietary protein or lysine on indices of lysine metabolism in liver, kidney, and heart of growing pigs1

Lysine addition to swine diets via either feed-grade lysine or protein sources costs producers. To better understand how diet affects lysine oxidation (LOX), weanling pigs were fed a control (C), high protein (HP), low protein (LP), high lysine (HL), or low lysine (LL) diets. No diet-induced alterations in lysine catabolism were detected in heart or kidney (P > 0.05). Liver lysine α-ketoglutarate reductase (LKR) (P < 0.05), saccharopine dehydrogenase (P < 0.05) activities, and α-aminoadipate δ-semialdehyde synthase abundance (P < 0.01) were reduced by 30%, 35%, and 52%, respectively, in pigs consuming LL compared with pigs consuming C. Expression of ornithine carrier-1 (ORC-1) mRNA in pigs fed HL was 170% greater (P < 0.05) than that in pigs fed C, whereas expression of the ORC-1 mRNA in pigs fed LL was 50% lower (P < 0.05) than that in pigs fed C. Expression of ORC-2 mRNA in pigs fed HL was 88% higher (P < 0.05) than that in pigs fed LL. The ORC transporters and LKR phosphorylation are likely points of r...