Study The Ratios Of Threonine And Tryptophan Of Low-protein Diets In Weaned Piglets

A study was carried out to investigate the optimum ratios of threonine and tryptophan of ideal amino acid pattern and effect of reducing the dietary CP content on performance and available energy in weaned piglets. Eighty crossbred pigletsfYorkshire X Landrace X Duroc] were allotted randomly by gender, litter and weight (average initial body weight of 9.7kg) into 20 groups and then distributed into 5 treatments: Dietl was the positive treatment with high protein content(phase I , II CP content 20.4,18.8% respectively). The diets from 2 to 5 were low protein treatments(phase I , II CP content 17.5,15.9% respectively) with different threonine/trytophan ratios(lysine 100) on the true digestible basis: 62:16, 65:16, 62:20 and 65:20 respectively. There were four replicates with four pigs per replicate in one treatment. Food intake, daily gain and diarrhea were recorded. The period of experiment was 28 days, dividing into two phases. The phase I ,11 diets contained 1.01,0.93% true digestible lysine respectively. After growth experiment, 6 middleweight pigs in per treatment were picked out for metabolism experiment, in which nitrogen retention, nitrogen digestion efficiency and utilization efficiency were evaluated.The results indicated that growth performance and nitrogen retention of Thr/Trp(62:20) treatment was optimal, Thr/Trp(65:20) treatments or high-crude protein were second, and Thr/Trp(65:16) treatment was lowest. The Thr/Trp(65:16) treatment had the lowest daily feed intake and daily gain compared with Thr/Trp(62:20),Thr/Trp(65:20) treatments (P<0.01) and high-crude protein treatment (P<0.05), and lower daily feed intake compared with Thr/Trp(62:16) treatment (P<0.05).There was no difference of nitrogen digestion efficiency among treatments. The nitrogen utilization efficiency of high-crude protein treatment was lowest compared with Thr/Trp(65:16) treatment (P<0.05) and other treatments (P<0.01). According to whole-stage performance and nitrogen metabolism, the optimum ratio of Thr/Trp on the true digestible basis was (62-63): 20 for 9.7-22.2 kg piglets.The results showed that, the low protein diets reduced 3 percentage units CP by supplementing adequacy crystalline amino acids, not only can maintain similar or comparable growth performance to the high protein treatments, but also can increase nitrogen utilization efficiency 13.1%, reduce nitrogen excreted 29.1% and decrease diarrhea frequency 70.9%. Low protein diets can improve energy utilization efficiency from ME to NE, increase NE 2.1%, decrease ratio Dlys/NE 2.2% compared with the high protein diet.