Effect Of Enzyme Preparations On Endogenous Enzmye Activity And Nutrient Metabolism Of Hens During Late Laying Period

The aim of this study was to evaluate the effect of enzyme preparations on performance, egg quality, serum parameters, nutrient metabolism, endogenous enzyme activity and related gene expression of hens during late laying period. The study includes four trials and the general results are presented as follows:Trial1:The screening of enzyme formulations was done by determining the effect of enzyme preparations on performance, egg quality and serum parameters of hens during late laying period.180049-wk-old ISA Brown hens were randomly allocated to10groups, and each group had6replicates with30hens per replicate. The hens in the control group were fed corn-soybean based diet, and the hens in nine trial groups were fed basal diet supplemented with E1～E9. All the trial groups except E3, E5and E6had a higher laying rate and a lower feed:egg ratio than control group, but egg weight and feed intake were not affected by enzyme supplementation. Broken eggshell rate and mortality were reduced by El, E7and E8. Egg shape index was increased by E5and E9at4wk(P<0.05) as well as E8and E3at11wk(P<0.01or P<0.05). Enzyme supplementation did not affect eggshell breaking strength, but eggshell thickness was reduced by E6at11wk and by E3at17wk(P<0.05). Haugh unit was improved by E1and E9at4wk and by E4and E6at7wk(P<0.05). E7increased TP, ALB, G and Ca content in serum at9wk(P<0.05). Serum ALB content was also increased by E8and E9at9wk(P<0.05), but E1had a lower serum G content than the control group(P<0.05). El and E9increased serum GOT activity at9wk, and serum U content was reduced by E7and E8(P<0.05). All the serum parameters did not differ significantly at17wk. The data show that El, E7and E8may have a better effect of improving performance of hens.Trial2:To validate the beneficial effect of enzyme preparations,72058-wk-old ISA Brown hens were randomly allocated to four groups, and each group had6replicates with30hens per replicate. The hens in the control group were fed corn-soybean based diet, and the hens in three trial groups were fed basal diet supplemented with E1, E7or E8. Compared to the control group, El slightly improved laying rate, but decreasd egg weight. However, E7and E8had a slightly lower laying rate but a higher egg weight than the control group. Feed intake, feed:egg ratio and broken eggshell rate did not differ among all groups. Enzyme supplementation tended to reduce eggshell thickness but improve eggshell breaking strength, and significantly increased Haugh unit(P<0.05). E1increased serum TG content(P<0.05), but other serum parameters were not affected by enzyme supplementation.Trial3:To determine the effect of enzyme preparation on nutrient digestibility and digestive enzyme activity of hens during late laying period, thirty-six58-wk-old ISA Brown hens were randomly allocated to2groups, and each group had6replicates with3hens per replicate. The hens were fed corn-soybean based diet with or without El. Compared to the control group, El improved apparent digestibility of CP, EE and Ca(P<0.05), and that of other nutrients as well as AME were also slightly improved. The activities of amylase, trypsin and lipase in the intestine did not differ between two groups, but duodenal lipase activity(U/g digesta) in the trial group tended to be higher than that in the control group(P=0.087). Protease activity(U/g digesta dry matter) in jejunum was higher in the trial group than in the control group(P<0.05), which was also slightly increased in duodenum and ileum. Compared to the control group, the activities of pancreatic digestive enzymes were slightly lower in the trial group, but maltase and sucrase activities in jejunal mucosa were slightly higher.Trial4:This trial was conducted to determine the effect of enzyme supplementation on pancreatic enzyme gene expression. The materials and methods used were the same as that in trial3. E1tended to reduce the mRNA levels of amylase and trypsinogen in pancreas, but the difference was not significant.