The Effects Of Liquid Methionine Hydroxy Analogue On Ascites Syndrome Of Broilers Induced By Low Temperature

The objective of this study was to investigate the effects of dietary liquid methionine hydroxyl analogue (DL-HMTBA) supplementation under two kinds of ambient temperature on growth performance, antioxidant capacity, related gene expression and ascites syndrome (AS) of broilers aged from 7 to 28 d of age. Eight hundred 7-d-old broilers were randomly assigned to 2 temperatures (low ambient temperature, LAT. and normal ambient temperature, NAT) and 4 dietary DL-HMTBA supplementation (0,0.17. 0.34 and 0.51%) in a 2 X 4 factorial arrangement (8 replicate pens; 10 birds/pen). The methionine content in basal diets was 0.50%. Broilers under LAT were raised at 14 to 16℃, whereas birds under NAT condition were raised at 24 to 26℃ during 7 to 28d.The results showed:(1) The LAT conditions significantly decreased (P<0.05) body weight gain (BWG), average daily feed intake (ADFI), and markedly increased (P<0.05) feed/gain (F/G). The interaction of temperature and DL-HMTBA supplementation were significant on F/G during d 22-28 (P<0.05). ADFI (22-28(1, NAT) and BWG, F/G (7-28d, LAT) exhibited quadratic trend with dietary DL-HMTBA increased.(2) The LAT environment significantly increased heart index at d21 and d28. Supplementing DL-HMTBA to diets decreased (P<0.05) heart index at 28d of age. HI (14d, LAT; 28d, NAT) exhibited linear trend with dietary DL-HMTBA increased.(3) The LAT environment significantly increased (P<0.05) the red blood cell count (RBC), hematokrit (HCT) and mean corpuscular hemoglobin (MCH) levels at 21 d of age. Adding DL-HMTBA decreased (P<0.05) the RBC, HCT, and MCH level at 2Id of age. The interaction of temperature and DL-HMTBA on RBC was significant at 14d of age (P<0.05). RBC, HCT and MCH at 14d of age exhibited quadratic trend with dietary DL-HMTBA increased.(4) The LAT condition decreased (P<0.05) GSH content (14d serum,21d lungs), superoxide dismutase activity (14,28d serum), glutathione peroxidase activity (14d serum, 21 d serum and lungs); increased (P<0.05) MDA content (14,21d serum and lungs) and protein carbonyl level (14,21 and 28d serum, liver and lungs). The interaction for GSH-Px activity (28d serum and lungs), malonaldehyde content (14d liver), superoxide dismutase activity (28d liver), total antioxidant capacity (14d liver) and GSH content (21d lungs) between temperature and DL-HMTBA were significant (P<0.05). Under low ambient temperature, GSH content (14,21d) and GSH-Px (14,28d) exhibited linear increased and total antioxidant capacity (28d) exhibited quadratic trend with dietary DL-HMTBA increased. Under normal ambient temperature, glutathione peroxidase activity (14,21d), total antioxidant capacity and protein carbonyl level exhibited quadratic trend, while malonaldehyde content (14d) increased with dietary DL-HMTBA increased.(5) The LAT condition significant increased (P<0.05) the mRNA expression of cystathionineβ-synthase (14 and 28d), methionine adenosyltransferase Ⅰ (28d), γ-glutamylcysteine synthetase (14d), GSH-reductase (28d), nuclear factor-kappa B (14d), vascular endothelial growth factor receptor-2 (21d) and GSH- synthetase, and decreased (P<0.05) the mRNA expression of γ -glutamylcysteine synthetase (14,21d), GSH-synthetase (28d) expression quantity. Adding DL-HMTBA increased (P<0.05) GSH-reductase (14d), vascular endothelial growth factor receptor-2 (21d) and GSH- synthetase (28d). The interaction of temperature and DL-HMTBA addition on the mRNA expression of cystathionine β-synthase,γ-glutamylcysteine synthetase, GSH-synthetase, GSH-reductase, methionine adenosyltransferase Ⅰ and nuclear factor-kappa B at 28 day of age was significant (P<0.05). Under low ambient temperature, the mRNA expression of cystathionineβ-synthase (28d) exhibited quadratic trend, and γ-glutamylcysteine synthetase (28d), nuclear transcription factor e2-related factor 2 (14d), methionine adenosyltransferase I (28d), GSH-reductase (28d) linearly decreased under normal temperature with dietary DL-HMTBA increased.(6) Under low temperature or normal temperature, the optimal supplementation of DL-HMTBA of basal diet which contained 0.5% Met was 0.25-0.30% or 0.23-0.29% based on growth performance, blood parameters and antioxidative ability by quadratic regression.The results suggested that LAT decreased growth performance, antioxidant ability and antioxidant gene expression changed methionine metabolism and blood parameters, induced the development of AS in broilers. DL-HMTBA supplementation increased antioxidant capacity, effectively promoted antioxidant gene expressive quantity, relieved the occurrence of ascites syndrome in broilers..