Production‐cycle‐related changes in indices of lysine catabolism in turkey liver

Abstract

In typical turkey production diets, lysine is frequently the second limiting amino acid. Understanding its catabolism could provide opportunities to increase the efficiency of lysine use for protein synthesis. We hypothesize that indices of lysine catabolism in turkey liver vary throughout the production cycle. Two commercial strains of turkey, Hybrid and Nicolas, were analyzed 8 times over a period of 17 weeks (n=8 birds/sampling time/strain) for lysine α‐ketoglutarate (LKR) and saccharopine dehydrogenase (SDH) activity and mRNA abundance, in vitro lysine oxidation (LOX) and amino acid oxidase (AAOX) activity. We found differences in LKR mRNA (P<0.01), SDH activity (P<0.05) and LOX (P<0.0001) and a trend for differences in LKR activity (P=0.09), SDH mRNA (P=0.07) and AAOX activity (P=0.06) throughout the production cycle. No consistent strain differences were detected for any variable. Interestingly, the average LKR and SDH activities across strains and weeks was 230 and 400 nmol per minute per gram of liver, respectively, as opposed to the average AAOX activity and LOX was 1.25 and 13.6 nmol per minute per gram liver, respectively. These data indicate that the saccharopine‐dependent pathway is the predominant pathway of lysine degradation in turkey liver and that indices of hepatic lysine catabolism vary throughout the production cycle. (Support; HATCH WVA 470, Virginia Poultry Growers Cooperative)