Effect Of Basal Diet Types And Crude Protein Levels On The Determination And Additivity Of Ileal Amino Acids Digestibility In Growing Pigs

This experiment uses in vivo digestion method to study the effects of different basal diet types and dietary crude protein(CP)levels on the determination and additivity of ileal digestibility of nitrogen(N)and amino acids(AA).The study was conducted to provide the certain theoretical basis for formulating pig diets.The experiment included two parts:The EXP.1 was conducted to investigate the effects of basal diet type on the determination of true ileal digestibility(TID)of N and AA for growing pigs.A total of 32 barrows(initial BW,28.9±0.7 kg)fitted with T-cannulas were used in an 8 × 2 incomplete Latin square design including 8 diets and 2 digestibility tests.The 8 experimental diets consisted of 2 types of basal diet(cornstarch or corn),and 4 graded levels of soybean meal(0,130 g/kg,260 g/kg or 390 g/kg).Each test consisted of a 5-d adjustment period and a 2-d ileal digesta collection period.The result showed that values of TID of N and all AA for growing pigs determined by the regression method were not affected by the basal diets type(P>0.05).And results obtained from the difference method show that,pigs fed the corn basal diet had greater TID of N and Gly compared with that for pigs fed the cornstarch basal diet,whereas the TID of Met and Lys were lower for pigs fed the corn basal diet than the cornstarch basal diet(P<0.05).In addition,other AA TID was not effected by basal diet type(P>0.05).In summary,the determination of TID of N and AA for growing pigs was not affected by the type of basal diet.The EXP.2 was conducted to investigate the effect of dietary CP level on the additivity of standardized ileal digestibility(SID)of AA in practical diets containing multiple protein sources for growing pigs.Twenty-eight barrows(initial BW,66.4±1.3 kg)were surgically fitted with simple T-cannulas at the distal ileum and assigned to a duplicated 14 × 4 incomplete Latin square design with 14 diets and 4 periods.The 14 experimental diets consisted of a nitrogen-free diet;a corn based semi-purified diet formulated to contain CP 80 g/kg;nine semi-purified diets containing soybean meal,canola meal,or corn distillers dried grains with solubles(DDGS)each supplying CP 80 g/kg,120 g/kg,or 160 g/kg;three mixed diets based on corn,SBM,CM,and corn DDGS formulated to contain CP 120 g/kg,160 g/kg,or 200 g/kg.Each test consisted of a 5-d adjustment period and a 2-d ileal digesta collection period.The results showed that dietary CP level could affect the AID of AA for growing pigs(P<0.05),but had no effect on the SID of AA(P>0.05).Determined values for AID of N and most AA for mixed diets were higher(P<0.05)than the predicted AID,illustrated that the AID of AA was not additive.Except for several AA,determined values for SID of N and most AA for mixed diets were consistent with(P>0.05)predicted SID values,illustrated that the SID of AA was additive.In summary,the additivity of SID values for AA of the mixed diets at different CP levels(120 g/kg,160 g/kg or 200 g/kg)was not affected by the CP levels of semi-purified diets(80 g/kg,120 g/kg or 160 g/kg).