| The purpose of this study is to explore the change rules of pancreas and intestinal digestive enzyme activities and intestinal tissue structure of pigeons aged 1 to 28 days.On this basis,to study the effects of dietary different levels ofAspergillus niger protease on the growth,intestinal digestive enzyme activities,nutrients utilization of pigeons and egg laying performance of breeding pigeons,in order to provide reference for pigeon production.The experiment was divided into three parts1.Explore the change rules of pancreas and intestinal digestive enzyme activities,and intestinal tissue morphology development for squabsHealthy squabs with similar weight aged 1,3,5,7,11,14,17,21 and 28 days were randomly selected and each day with 6 squabs,then slaughtered after weighing,measured intestinal length,and made intestinal sections to observe tissue morpholog;determined pancreatic and intestinal digestive enzyme activities.The results showed that:(1)Pigeon weight increased significantly within 1 to 21 days of age(P<0.05),and the first two weeks grew faster than the latter two weeks.(2)The length of duodenum,jejunum and ileum of pigeons increased significantly within 1 to 17 days of age(P<0.05).The growth rate of jejunum and ileum in the first two weeks was faster than that in the duodenum,and the growth rate of all three tended to be consistent in the latter two weeks.The villus height of duodenum,jejunum and ileum increased significantly within 1 to 14 days of age(P<0.05),duodenal recess depth increased significantly within 5 to 14 days of age(P<0.05),jejunum recess depth increased significantly within 1 to 7 days of age(P<0.05),ileum recess depth increased significantly within 1 to 14 days of age(P<0.05),and then decreased,but remained higher than 1 to 7 days of age(P<0.05);The myometrium thickness of duodenum and ileum increased significantly within 1 to 5 days of age(P<0.05),and the myometrium thickness of jejunum increased significantly at 1 to 3 days of age.The changes of villi height,crypt depth and myometrium thickness growth rate of duodenum,jejunum and ileum were not consistent with the increase of age,but it can be found that it was a rapid development of intestine during 1 to 5 days of age.(3)Amylase content in the pancreas and jejunum was higher.Amylase activity of the pancreas at 1～11 days of age was significantly higher than that of 14～28 days of age(P<0.05).Amylase activity of the duodenum and jejunum increased significantly with age(P<0.05),and amylase activity of the ileum increased significantly at 17 days of age(P<0.05).(4)Pancreatic and duodenal lipase activity decreased significantly at 14 days of age,followed by a steady trend after 14 days of age(P<0.05);Jejunal lipase activity increased significantly with age and peaked at 3 and 11 days of age(P<0.05);Ileal lipase activity was lowest and decreased significantly with age and then decreased at 14 days of age(P<0.05).(5)There was a significant decrease in pancreatic trypsin activity at 3 and 11 to 17 days of age(P<0.05).The activity of trypsin in duodenum and ileum increased significantly with age(P<0.05),but the change trend of trypsin activity in duodenum was stable at 11 to 28 days of age,and the jejunum was stable after 14 days of age.Ileal trypsin activity was the lowest at 17～28 days of age(P<0.05).(6)Pancreatic chymotrypsin activity decreased significantly at 11 to 14 and 21 to 28 days of age(P<0.05),duodenal chymotrypsin activity increased significantly with age(P<0.05),reached the maximum at 5 days of age,and decreased significantly at 11 days of age(P<0.05),finally changed steadily,jejunal chymotrypsin activity was extremely low and decreased significantly at 14 days of age(P<0.05).2.Effects of Aspergillus niger protease on body weight,intestinal digestive enzyme activities of squabs and laying performance of breeding pigeonsA total of 120 pairs breeding pigeons under the same breeding cycle and 240 1d old healthy squabs were selected and randomly divided into 4 groups with 6 replicates in each group,5 pairs breeding pigeons and 10 squabs in each replicate.The experiment was divided into four test groups,namely,the base diet group(A),150mg/kg protease addition group(B),300mg/kg protease addition group(C),600mg/kg protease addition group(D).The base diet consists of 50%granular feed and 50%grain,and Aspergillus niger protease is added to the granular.The test period was 28 days.The results showed that:(1)Compared to the control group,the addition of different levels of Aspergillus niger protease had no effect on the body weight of 14 and 28 day-old pigeons(P>0.05),but significantly increased the ADG at 14～28 days of age(P<0.05).(2)Adding 300 mg/kg protease significantly increased the relative weight of the bursa.(3)Adding 150 mg/kg protease significantly increased the activities of amylase and chymotrypsin in jejunum and ileum and lipase in duodenal(P<0.05),but decreased the activities of lipase in jejunum and ileum;adding 300 mg/kg protease significantly decreased the activities of amylase,lipase and trypsin in duodenum and chymotrypsin in ileum(P<0.05);adding 600 mg/kg protease significantly reduced duodenal amylase,trypsin,and chymotrypsin activity(P<0.05),as well as jejunal and ileal lipase activity and duodenal and ileal chymotrypsin activity(P<0.05).(4)The addition of different levels of exogenous protease had no significant effect on laying interval,laying ratio and fertilization rate of breeding pigeons(P>0.05).3.Effect of Aspergillus niger protease on the body weight,slaughter performance,serum biochemical index,relative weight of visceral organs,intestinal digestive enzyme activities,mRNA expression level of protease-related genes and nutrient availability in pigeonsA total of 25 day-old 240 squabs were randomly selected and taken away from parental pigeons and kept separately.240 squabs were randomly divided into 4 groups and 6 replicates at 28 days old.Pigeons were kept to 56 days old.Diets design were the same as the second part.The results showed that:(1)The body weight in 600 mg/kg protease group was highest(P<0.05).(2)The half-net bore rate and pectoral muscle rate in 150 and 600 mg/kg protease group were significantly higher than those of the control group(P<0.05),and the pectoral muscle rate in 300 mg/kg protease group was also significantly improved(P<0.05).(3)Adding 300 mg/kg protease significantly reduced duodenal amylase activity(P<0.05).(4)Adding 150 mg/kg protease in the diet upregulated the expression of jejunal trypsin and chymotrypsin mRNA(P<0.05).Adding 300 mg/kg protease upregulated the expression of pancreatic and jejunal trypsin and chymotrypsin mRNA(P<0.05).Adding 600 mg/kg protease significantly down-regulated the expression of jejunal chymotrypsin mRNA(P<0.05).(5)Adding 150 and 300 mg/kg protease significantly increased the apparent utilization of crude protein(P<0.05).Adding 600 mg/kg significantly reduced the apparent utilization of threonine,glycine,alanine,methionine and leucine(P<0.05).To sum up,the changes of digestive tract enzyme activity and intestinal tissue structure of 1～28 days old pigeon and the addition ofAspergillus niger protease in feed diet were studied,and the results showed that 14 days old was the inflection point of the change of growth rate and digestive enzyme activity of pigeon;Adding 150 and 300 mg/kg Aspergillus niger protease could enhance intestinal digestive enzyme activity and improve the utilization rate of feed protein;Adding 600 mg/kg protease reduced the activity of intestinal digestive enzyme and the utilization rate of amino acids in pigeon. |
