Abstract
L-carnitine promotes mitochondrial ${\beta}$-oxidation of long chain fatty acids and their subsequent transport across the inner mitochondrial membrane. Although the role of L-carnitine in fatty acid metabolism has been extensively studied, its role in live performance and carcass responses of commercial broilers is less understood. The objective of this research was to determine if Lcarnitine fed at various levels in diets differing in CP and amino acids impacted on live performance and carcass characteristics of commercial broilers. Two floor pen experiments were conducted to assess the effect of dietary L-carnitine in grower diets. In Exp. 1, Ross${\times}$Hubbard Ultra Yield broilers were placed in 48 floor pens (12 birds/pen) and fed common diets to d 14. A two (0 or 50 ppm Lcarnitine) by three (173, 187, and 202 g/kg CP) factorial arrangement of treatments was employed from 15 to 35 d of age (8 replications/treatment). An interaction (p<0.05) in carcass yield indicated that increasing CP (187 g/kg) resulted in improved yield in the presence of L-carnitine. Increasing CP from 173 to 202 g/kg increased (p<0.05) BW gain and decreased (p<0.05) feed conversion and percentage abdominal fat. Feeding dietary L-carnitine increased back-half carcass yield which was attributable to an increase (p<0.05) in thigh, but not drumstick, yield relative to carcass. In Exp. 2, $Ross{\times}Ross$ 708 broilers were fed common diets until 29 d. From 30 to 42 d of age, birds were fed one of seven diets: i) 200 g/kg CP, 0 ppm L-carnitine; ii) 200 g/kg CP, 40 ppm L-carnitine; iii) 180 g/kg CP, 0 ppm L-carnitine; iv) 180 g/kg CP, 10 ppm L-carnitine; v) 180 g/kg CP, 20 ppm L-carnitine; vi) 180 g/kg CP, 30 ppm L-carnitine; and vii) 180 g/kg CP, 40 ppm L-carnitine (6 replications of 12 birds each). BW gain, feed conversion, mortality (30 to 42 d), and carcass traits (42 d) were measured on all birds by pen. There were no treatment differences (p<0.05). However, the addition of 40 ppm L-carnitine in the 200 g CP/kg diet increased (p = 0.06) thigh yields relative to BW in comparison to birds fed diets without L-carnitine, which was further confirmed via a contrast analysis (0 vs. 40 ppm L-carnitine in the 200 and 180 g CP/kg diets; p<0.05). These results indicated that dietary L-carnitine may heighten metabolism in dark meat of commercial broilers resulting in increased relative thigh tissue accretion without compromising breast accretion.