| Five experiments were conducted to study the effects of dietary L-carnitine and coenzyme Q10 (CoQ) supplementation alone and in combinationon on broiler's ascites susceptibility, and the related mechanisms were discussed. 1) To determine the effects of L-carnitine and CoQ on growth performance and ascites susceptibility of broilers. A 3x3 factorial arrangement was employed with 3 levels of L-carnitine (0, 75 and 150 mg/kg) and 3 levels of CoQ (0, 20 and 40 mg/kg) supplementation during the experiment. Five hundred and forty one-day-old Arbor Acre (AA) male broiler chicks were randomly allocated into nine groups with six replicates each. From day 8, the diets were supplemented with L-carnitine and CoQ, respectively. From day 15 to day 21, all birds were exposed to low ambient temperature (15-18℃) to induce ascites. The results showed that growth performance of broilers were not significantly affected by CoQ or L-carnitine + CoQ supplementation, but body weight gain (BWG) of broilers was significantly reduced by 150 mg/kg L-carnitine. Ascites susceptibility and mortality of broilers were significantly decreased by L-carnitine, CoQ and L-carnitine + CoQ supplementation (P<0.05). 2) To study the effects of L-carnitine and CoQ supplementation on lipid metabolism and antioxidative capability of ascites broilers. The results showed that there were significant effects observed on TG, TC, HDL-C, LDL-C and VLDL-C in liver tissue by L-carnitine + CoQ supplementation together (P<0.05). T-SOD activity in liver tissue was significantly increased and MDA content was reduced by L-carnitine + CoQ supplementation together (P<0.05), which means L-carnitine and CoQ supplementation can improve lipid metabolism and antioxidative capability of ascites broilers. 3) To investigate the effects of L-carnitine and CoQ supplementation at different ages on performance, abdominal fat deposit and immune responses in ascites-susceptible broilers. 3×2×2 factorial arrangement were used, and the factors included 3 levels of L-carnitine (0, 75, 150 mg/kg), 2 levels of CoQ (0 and 40 mg/kg) and 2 supplementation ages (from day 1 and from day 10, respectively). Four hundred eighty 1 day-old Avain male broiler chicks were randomly allocated into 12 groups with 5 replicates each, 8 birds per replicate. The results showed that abdominal fat ratio at 0-3 wk was significantly reduced, and thymus index at 3-6 wk was increased by L-carnitine + CoQ supplementation together (P<0.05). Serum lysozyme activity was increased by L-carnitine + CoQ. The peripheral blood lymphocyte proliferations in response to ConA and LPS were not influenced by L-carnitine alone, but the proliferation in response to ConA was significantly decreased by CoQ and L-carnitine + CoQ (P<0.05). 4) To investigate the effects of L-carnitine and CoQ supplementation under different treatments on hepatic mitochondrial function, respiratory chain-related enzymes' activities in ascites-susceptible broilers. Four hundred eighty 1-d-old Avain male broiler chicks were fed with corn-soybean based diets for 6 wks in a 3x2x2 factorial experiment, and the factors consisted of L-carnitine supplementation (0, 75 and 100 mg/kg), CoQ supplementation (0 and 40 mg/kg) and EschErichia coli lipopolysaccharide challenge (LPS and saline). L-carnitine and CoQ were supplemented from day 1. From day 18, the broilers received 3weekly i. p. injections of LPS (1.0 mg /kg BW) or an equivalent amount of sterile saline as the control. From day 10, all the birds were exposed to low ambient temperature (12-15℃) to induce ascites. The results showed that L-carnitine and CoQ supplementation alone and in combination reduces broilers' susceptibility to ascites, which might be realized via improving hepatic mitochondrial function, some respiratory chain-related enzymes activities and mitochondrial antioxidative capability. 5) To observe if there exists cardiomycyte apoptosis in ascites broilers, and investigate the effects of L-carnitine and CoQ supplementation. 2×2×2 factorial arrangement were used, and the factors included 2 lev...
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