| This experiment was conducted to study the effects of diets with different neutral detergent fiber(NDF)levels on growth performance,apparent digestibility of nutrients,gastrointestinal development of lambs.Sixty healthy newborn lambs(3.23±0.20 kg initial body weight)were selected and randomly divided into four groups,each group will consisted of 5 replications with 3 sheep per replication.The lambs were offered concentrates at 10 days of age,and NDF levels of concentrates were 12%(12NDF group),16%(16NDF group),20%(20NDF group)and 24%(24NDF group),respectively.During the trial period of 60 days,all lambs were breast-fed in the feeding test except for the digestion test.On the 55th day of the experiment,3 healthy lambs were selected for digestion and metabolism tests in each group.On the 20th,30th,and 60th days of the experiment,10 healthy lambs were selected from each group to weigh and collect blood to measure blood routine,antioxidant,and immune indexes.On the 3th,10th,20th,30th,and 60th days of the experiment,10 lambs from each group were selected to collect rumen fluid for testing pH and volatile fatty acids were measured.At the end of the test,each group randomly selected 5 healthy lambs for slaughter test.The results showed that:1)With the increase of the age,the body weight of the lambs in each test group increased significantly(P<0.01);the daily weight gain at each age stage was not significantly different(P>0.05).With different NDF levels,the dry matter intake of the lambs in each group was not significantly different(P>0.05).2)The digestibility of dry matter and organic matter in the 24NDF group were significantly lower than that of the 12NDF and 16NDF group(P<0.05),the apparent digestibility of gross energy in the 24NDF group was significantly lower than that in the 16NDF group(P<0.05).The apparent digestibility of NDF and acid detergent fibers in 20NDF and 24NDF groups were significantly higher than that in 12NDF group(P<0.05).3)During the test period(0?60 d),diets with different NDF levels had no significant difference on rumen pH and total volatile acid concentration of lambs between treatment groups(P>0.05).With the increase of NDF level,the concentration of acetic acid in lambs of 24NDF group was significantly higher than that of 12NDF,16NDF and 24NDF groups(P<0.05);the concentration of propionic acid of lambs in 12NDF group was significantly higher than that of 16NDF and 24NDF groups(P<0.01),but the concentration of butyric acid was significantly reduced(P<0.01),the value of acetic acid/propionic acid in 24NDF group was significantly higher than that in 12NDF,16NDF and 20NDF groups(P<0.01).4)During the test period(0-60 d),with the increase of NDF level,there was no significant difference in blood glucose,total protein,albumin,globulin of lambs in each test group.There were no significant difference in ?-hydroxybutyrate acid and non-esterified fatty acid contents of lambs in each test group(P>0.05).It had no significant effect on the blood total antioxidant capacity,glutathione peroxidation and malondialdehyde contents of lambs feeded with different NDF levels of diets(P>0.05).With the increase of NDF level,the activity of superoxide dismutase showed a decreasing-increasing-decreasing trend(P<0.05);it had no significant effect on the blood immunoglobulins A,immunoglobulins M and immunoglobulins G levels among treatment groups of feeding diets with different levels of NDF(P>0.05).5)The total weight of stomach,rumen and duodenum weight of 12NDF group were significantly higher than those of 16NDF,20NDF and 24NDF groups(P<0.05).The total stomach weight,rumen weight and duodenum weight of 16NDF,20NDF and 24NDF group tend to increase with the increase of NDF level.The rumen percentage of live weight before slaughter in 12NDF group was significantly higher than that in 16NDF,20NDF and 24NDF groups(P<0.05).The duodenum percentage of live weight before slaughter in the 12NDF group was significantly higher than that in the 16NDF group(P<0.05).Diets with different NDF levels had no effect on rumen epithelium thickness(P<0.05)of lambs;the rumen nipple length of lambs in the 12NDF group was significantly higher than that in the 20NDF group(P<0.05);the nipple width in the 20NDF group was significantly higher than that in the 24NDF group(P<0.05));the thickness of the stratum corneum in the 12NDF group was significantly higher than that in the 20NDF and 24NDF groups(P<0.01),and the 16NDF group was significantly higher than the 24NDF group(P<0.01),the difference between the 12NDF and 16NDF groups was not significant(P>0.05);the Mucosal thickness of lambs in the 24NDF group was significantly higher than that in the 12NDF and 16NDF groups(P<0.01).With the increase of NDF level,the thickness of the duodenal mucosa in the 24NDF group was significantly higher than that in the 12NDF,16NDF and 24NDF groups(P<0.01),and the villi length and villu length/crypt depth values in the 12NDF group were significantly higher than those in the 16NDF and 24NDF groups(P<0.01).Dietary NDF levels had no effect on the thickness of the jejunum intestinal wall,crypt depth,and mucosal thickness of lambs(P>0.05);with the increase of NDF level,the length of the jejunal villi in the 24NDF group was significantly higher than that in the 12NDF group(P<0.05),The villu length/crypt depth value of the 24NDF group was significantly higher than that of the 12NDF,16NDF,and 20NDF groups(P<0.01),and the 16NDF group was significantly higher than that of the 12NDF and 20NDF groups(P<0.01).The ileum crypt depth of lamb in 16NDF group was significantly higher than that in 24NDF group(P<0.05).Feeding diets with different NDF levels had no effect on the intestinal wall thickness of each intestinal segment(P>0.05).In conclusion,the optimal NDF level of diet for female lambs at the age of 0 to 60 days is 16%-20%. |
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