Effects Of 3 Proteases On Growth Performance,nutrient Apparent Digestibility And Serum Biochemical Indices Of Suhuai Weaned Piglets

As a biocatalyst that can degrade proteins,proteases are widely used in various industries such as washing,leather and feed industries.Proteases have different characters and biological functions due to the variety of sources,resulting in a wide variety of characterizations and applications of proteases.The method for determining the activity of proteases is uneven,and it needs to establish a sound industry standard.The application of different proteases in animal production also has different effects.The purpose of this experiment is to determine the enzymatic activities of different proteases and to apply them to the production of weaned pigs to explore the application effects and compare the action mechanisms of different proteases.The main findings are as follows:The national standard method(GB/T23527-2009)was used to determine the activity of proteases at different optimum p H conditions and the activity of keratinase.Alkaline extraction and acid precipitation method was used to extract the protein in soybean meal as a substrate for the determination of keratinase activity.Comparing the enzyme activity under different assay methods.The results showed that the accuracy of the determination of enzymatic activity using soybean protein as a substrate is lower than that of the national standard fortification method.The application of acidic,neutral and alkaline proteases to the production of piglets in Su huai was studied.The effects of three proteases on the growth performance,nutrient apparent digestibility and serum biochemical indices of the piglets were evaluated.In the trial,single-factor randomized block design was used to select 120 healthy,average-weighted 9.24±0.84 kg Suhuai weaned piglets,which were randomly divided into 4 groups with 6 replicates in each group and 5 pigs in each replicate according to the principle of uniform body weight and gender.The control(CT)groups of weaned piglets were fed a basal diet,and weaned piglets in the experimental groups were fed the diets supplemented with 0.2 g/kg acidic protease(Group Ⅰ),0.2 g/kg neutral protease(Group Ⅱ),and 0.1 g/kg alkaline protease(Group Ⅲ),respectively.The trial lasted for 45 days after 5 d adaptation.The results as follows:1)Compared with CT group,the final weight,average daily gain and average daily feed intake of group Ⅰ were significantly increased(P < 0.05),and the feed/gain(F/G)was decreased,but the difference was not significant(P > 0.05).The average daily gain was significantly increased in groupⅢ(P < 0.05)while feed/gain(F/G)was decreased significantly(P < 0.05);the dry matter digestibility and organic matter digestibility in the proteases treated groups were significantly higher than CT group(P < 0.05).The dry matter digestibility and organic matter digestibility in group Ⅰ and Ⅲ were significantly higher than that of group Ⅱ(P < 0.05).The crude protein digestibility of group Ⅰ was significantly higher than other groups(P < 0.05);On day 31~45 of the experiment,compared with the CT group,the diarrhea rate and the fecal index in proteases treated groups was significantly decreased(P < 0.05),the diarrhea rate and the fecal index in group Ⅲ were the lowest.2)Compared with CT group,the content of blood urea nitrogen(BUN)in group Ⅰ was significantly decreased(P < 0.05),there was no significant difference among the proteases treated groups(P > 0.05).The content of IgG in group Ⅱ was significantly higher than that in the CT group(P< 0.05),while there was no significant difference in other groups(P > 0.05).The content of IgM in group Ⅱ and Ⅲ was significantly higher than that in CT group(P < 0.05).The content of IgA in each group had no significant difference(P > 0.05);the activity of SOD in group Ⅱ was significantly higher than that in group Ⅰ and Ⅲ.(P < 0.05).The content of MDA in group Ⅱ and group Ⅲ were lower than that in CT group and group Ⅰ,but the difference was not significant(P > 0.05).The activity of GSH-Px in CT group and group Ⅱ were significantly higher than those in group Ⅰ and Ⅲ(P < 0.05).There was no significant difference in T-AOC among 4 groups(P > 0.05).The activity of CAT in group Ⅱ was significantly higher than that of group Ⅰ and group Ⅲ(P < 0.05),while the activity of CAT in CT group was also significantly higher than that of group Ⅲ(P < 0.05).The results indicated that the effect of acid protease in improving the growth performance and nutrient apparent digestibility of Su huai weaned piglets is better.Neutral protease and alkaline protease are more effective in reducing nutrient diarrhea,while neutral protease was most effective in improving immune and antioxidant properties.