Effects of supplementary dietary L-carnitine on performance and egg quality of laying hens fed diets different in fat level

The present study aimed to examine the effects of dietary L-carnitine supplementation on performance parameters and egg quality measurements of white Leghorn hens at two dietary fat levels. Two hundred 22-weeks old white Leghorn hens were randomly distributed into 40 cages of five birds each. Two basal diets different in added fat level (0 or 3%) were formulated and supplemented with incremental levels of L-carnitine (0, 50, 100, 150 mg/kg diet). The experiment lasted 98 d (two weeks for adaptation and 12 weeks as the main experimental period). At the final day of trial, ten randomly selected hens per treatment were euthanized to measure abdominal fat content. Dietary inclusion of 3% soybean oil caused a significant (P<0.05) increase in egg weight and egg mass, and decrease in feed consumption by the birds. Daily energy intake, however, was not affected by dietary fat supplementation. Except of feed conversion ratio, none of performance parameters were found to be influenced by dietary fat by carnitine interaction. Feed conversion ratio improved (P<0.05) when L-carnitine was supplemented to diets contained in 3% added fat. The albumen height and subsequently Haugh unit were improved (P<0.05) by dietary supplementation of L-carnitine, particularly the level of 150 mg/kg; however, eggshell quality indexes (thickness and breaking strength) were not affected by dietary L-carnitine inclusion, but influenced (P<0.05) by fat supplementation of diets. Moreover, dietary addition of fat increased abdominal fat percentage and supplementary dietary L-carnitine significantly (P<0.05) decreased abdominal fat and yolk cholesterol contents. From the present results, it can be seen that although the supplemental L-carnitine had no considerable effect on most performance parameters, it had a beneficial impacts on lipid metabolism and internal egg quality indexes of 24 to 36 wk-aged laying hens.