Effect Of Dietary Amino Acid Balance On Growth Performance And Nitrogen Excretion Of Growing Pigs

The effects of low-protein diets supplemented with essential amino acid on growth performance, nitrogen balance and nutrient digestibility of growing pigs were investigated in this study.The first part:Choice about 60 days of age and 192 three-line crossbred pigs(Duroc × Landrace × Yorkshine), with initial BW of 23.5±1.38 kg, and according to their days of age, weight, gender with the principle of consensus, they were randomly divided into four groups and each group has eight pigs with six repeats, the trial period is 35 days all together. The experiment used corn, soybean meal and DDGS as the main raw material, referring to NRC(2012) as well as the ideal model of amino acids, and adopted the standard ileal digestible amino acids and net energy system to formulated diets. In growing pigs, dietary CP level were 17%, 16%, 15% and 14% respectively, made balance among 5 kinds of essential amino acids, such as, Lys, Met, Thr, Try and Val. The 17% protein diet be treat as the control group and others as the experiment group. Chromium sesquioxide(Cr2O3)was as an indicator for digestion experiments, and the fecal samples be collected from each column. The main results of this experiment are as follows:1. Compared with the control group, the low-protein diets on growth performance of growing pigs was not significantly different(p>0.05). Under the condition of adding Lay, Met, Thr, Tryl, four kinds of essential amino acids, the level of dietary CP reduced to 14% that have no effect on the growth performance of growing pigs.2. Low protein diet could reduced the content of fecal N and fecal P, the apparent digestibility of N, P and Ca significantly increased. Reducing dietary CP level to 14% and 15%, fecal N content were respectively reduced by 7.4% and 6.2%; comparing with the control group, the CP of dietary’s content of phosphorus in manure for 14%, 15% and 16% respectively decreased by 1.5%, 6.0%, 3.8%, and the CP level to 15% was significantly different from the control group(p<0.05); When it comes to the CP of dietary for 15%, the apparent digestibility of phosphorus was higher than the control group(p<0.05); CP14% and 16% diet calcium apparent digestibility was significantly higher than control group and respectively improved by 6.4% and 4.7%( p<0.05), CP15% diet apparent digestibility of calcium was also higher, but the difference with the control group was not significant(p>0.05).3. Low-protein diets could significantly increase apparent digestibility of crude fat, crude fiber, dry matter and crude ash. When dietary crude protein level was 14% or 15%, the fecal fat content of the diet compared to the control group decreased by 22.4% and 20.2%, and the apparent digestibility of crude fat were significantly different from the control group(p<0.01); When dietary CP was 14% or 15%, the apparent digestibility of crude fiber was the highest and with significant differences compared with the control group(p<0.01), and it respectively improved by 17.4% and 16.7%; The apparent digestibility of dry matter increase with the decreasing of dietary crude protein level, in which CP14% of dietary dry matter apparent digestibility was highest, CP15% and 16% of the diet followed and all of them were significantly different compared with the control group(p<0.01); CP14% and 15% of the dietary fecal crude ash content were significantly lower than the control group(p<0.01), the two sets of crude ash apparent digestibility were the highest and there was a significant difference compared with the control group(p<0.01), respectively improved by 28.5% and 31.0%, there were also significant differences(p<0.01) between the CP 16% of the diet and the control group.The second part: Twenty-eight crossbred barrows(Landrace × Yarkshire) with age of 50 d were randomly assigned to four treatments,with seven individuals per treatment. Experimental diets and experimental design are same with the test one.Nitrogen balance trial began in 15 days of the whole test, the fecal and urine samples be collected from each cage. The results showed as follows: reduce the diet crude protein level can significantly reduce the emissions of urine nitrogen and total nitrogen(p<0.01);reduce the diet protein levels significantly improve nitrogen apparent biological value(p<0.05); the total nitrogen intake decreased with the lower protein levels(p<0.05); But each nitrogen deposition, deposition of nitrogen/intake and fecal excretion rate have no significant difference(p>0.05);diet protein level does not affect the apparent digestibility of nitrogen(p>0.05).