The effects of dietary L-carnitine supplementation on the performance, organ weights and circulating hormone and metabolite concentrations of broilerchickens reared under a normal or low temperature schedule

1. The present study examined the effects of the addition of 100 mg/kg L-ca rnitine to the basal starter (containing 17.8 mg/kg L-carnitine) and finish er (containing 22.9 mg/kg L-carnitine) diets on performance, organ weights and plasma hormone and metabolite concentrations of male and female broiler chickens. The broiler chickens were reared either in a room with a normal temperature (NT) program or with a low temperature (LT) program (rapid decr ease from 28 degreesC to 20 degreesC at 14 d of age). 2. Broiler chickens reared under the LT schedule consumed more food and att ained a greater body weight at 42 d of age than their counterparts reared u nder NT schedule, without any difference in food efficiency or abdominal fa t content. Dietary L-carnitine supplementation had no significant effects o n any of these production parameters, except for a reduction in the abdomin al fat content of female NT chickens. However, the LT schedule and dietary L-carnitine supplementation greatly increased absolute and proportional hea rt weights. The elevated heart weights were not due to right ventricle hype rtrophy. 3. Both the LT program and L-carnitine supplementation increased circulatin g plasma triiodothyronine concentrations. There were also some transient ef fects of both experimental variables on plasma growth hormone, glucose and triglyceride concentrations. 4. L-carnitine did not improve broiler performance. However, this result do es not mean that L-carnitine supplementation cannot have beneficial effects in other circumstances. In view of the elevated proportional heart weights , it can also be argued that L-carnitine is a potential agent for reducing the incidence of metabolic diseases in broiler chickens.