Study On Valine Requirement Of Broiler Chicken From 1 To 42 Days Of Age

This study was conducted to investigate the effect of low protein diets supplemented with valine on growth performance,carcass yield,nutrient digestibility,serum biochemical indices,antioxidant capacities,and glycogen content of male broilers,and to recommend the requirement of Valine in commercial diets for broiler chicken.This research can provide a theoretical basis for the precise design of the broiler diet.Experient 1,A total of 300 Arbor Acres male broilers in the starter phase were distributed in a completely randomized design with five treatments consisting of six replicates of 10,respectively.The levels of dietary total lysine(Lys)was 11.7 g/kg and crude protein was 20% for the starter phases.Dietary Val/Lys(total basis)was supplied from 68% up to 88% in 5% increments for the starter phase.Dietary Val supplementation linearly(P<0.01)and quadratically(P<0.01)increased the average daily weight gain(ADG),while the feed conversion ratio(FCR)decreased linearly(P<0.05)or quadratically(P<0.05)as the inclusion of Val/Lys level creased.Requirements of ratios of valine to lysine(Val/Lys)were estimated using quadratic regressions and the broken line model.Estimations of requirements were of 82.1% and 78.3% Val/Lys for ADG while 82.1% and 77.4% for FCR in starter phase.The apparent total tract digestibility(ATTD)of crude protein(CP)increased linearly or quadratically(p<0.01)while the concentrations of malondialdehyde(MDA)decreased linearly or quadratically(p<0.1)with an increased Val/Lys ratio.The concentrations of total protein(TP)and albumin(ALB)increased quadratically(P<0.1)with increasing Val/Lys level,and the highest concentrations of TP and ALB were obtained at the 83% Val/Lys level.Therefore,the recommended level of Val/Lys in the low-protein diets for broilers in the starter phase was 80.0%,corresponding to 0.94% total Val.Experient 2,A total of 300 Arbor Acres male broilers in the grower phase were distributed in a completely randomized design with five treatments consisting of six replicates of 10,respectively.The levels of dietary total Lys was 1.01 g/kg and crude protein was 18% for the starter and grower phases.Dietary Val/Lys(total basis)was supplied from 70% up to 90% in 5% increments for the grower phase.The ADG increased quadratically(P<0.01)and the FCR decreased quadratically(P<0.01)as dietary Val/Lys level increase from 70% to 90%.Estimations of requirements were of 77.8% Val/Lys for ADG while 80.9% and 77.0% for FCR in starter phase.when the Val/Lys level was 80%,the apparent total tract digestibility(ATTD)of crude protein(CP)were better than other treatments,besides the concentrations of malondialdehyde(MDA)decreased linearly.Moreover,the highest serum T-SOD activities occurred in the 80% treatments.There were no significant effect on cholesteric(TC),triglyceride(TG),total protein(TP),albumin(ALB),globulin(GLB)and uric acid(UA).Therefore,the recommended level of Val/Lys in the low-protein diets for broilers in the grower phase was 79.2%,corresponding to 0.80% total Val.Experient 3,The broilers of experient 1 continued to be raised to the 42-day-old with the same of the Val/Lys levels.The levels of dietary total Lys was 1.01 g/kg and crude protein was 18%.The ADG increased quadratically(P<0.05)and the FCR decreased quadratically(P<0.05)as dietary Val/Lys level increase from 63% to 88%.The concentrations of malondialdehyde(MDA)Significantly decreased when the diet Val level were 78% and 83%.The serum glucose(GLU)content higher than contron treatments.The diet Val level have no effect on the slaughter performance of broilers and free amino acids in serum.