| In order to protect the ecological environment,the breeding of cashmere goats in Western China has changed from grazing in pastoral areas to house-raising.But there are some limitations of house-raising,it may not only lead to insufficient nutrient intake in cashmere goats but also restrict the growth and development of lambs.At present,the relevant feeding standards has not promulgated for cashmere goats.Therefore,it is particularly important to explore the effects of different weaning ages,energy and protein nutrition levels on the growth and development of northern Shaanxi white cashmere goats and the mechanism of action.In the experiment,fifty-four Shaanbei white cashmere female goats aged 54 days?average body weight was 10.73±1.03kg?were selected and randomly assigned to 6 groups,with 3 replications per group and 3 goats for each repetition.Group ?,Group ?,and Group ? were fed standard diets,and the weaning age was 90 d,75 d,and 60 d,respectively.Goats in Group ?,Group ?,and Group ? were all weaned at 60 d,and the energy and protein level of their diet was 85%,115%and 130%that of the standard diet,respectively.After 180 days experiment period..Three digestion and metabolism trails were conducted at the age of 114-120 d,144-150 d,174-180 d,respectively.One goat?a total of 18 goats?was randomly selected from each replication for a 3-phase digestion and metabolism test,and samples of feed,feces and urine were collected to measuring the apparent digestibility,rate of energy and nitrogen utilization of main nutrients.The main results were as follows:1.The average daily weight gains of the group ??? and ? of weaned lambs were 95.97,104.58,and 108.75 g·d-1,respectively.The value of Group ? was significantly higher than that of Group I?P<0.05?.The dry matter intake of Groups ? and ? was significantly higher than that of Group ??P<0.01?;The intake energy,the digestive energy,the metabolic energy,the digestible nitrogen,the sedimentary nitrogen and the apparent nitrogen deposition rate of4-6 months old weaned lambs were significantly increased in the group ??P<0.05?;With the increase of dietary nutrient levels,the dry matter intake and the average daily weight gains of 4-6 months old weaned lambs were increased first and then decreased?P<0.05?;The dietary nutrition level significantly affected the digestion and metabolism of DM,EE,NDF,ADF,Ca,P,N and energy?P<0.05?;Except for DM,the digestive and metabolic rates of EE,NDF,ADF,Ca,P,N and energy increased with age increasing.2.Weaning age and dietary nutrition significantly affected villi height,villi width,crypt depth,muscular layer thickness,villi surface area of the small intestine?P<0.05?;In the meantime,the activities of alpha-amylase,sucrase,lipase,trypsin and chymotrypsin in small intestine were significantly affected by weaning age and dietary nutrition level?P<0.05?.3.The relative expression levels of y+LAT1,SLC3A1 and PepT1 mRNA in the small intestine were in the ileum>jejunum>duodenum;With the increase of dietary nutrient levels,The relative expression of y+LAT1,SLC3A1 and PepT1 mRNA in the small intestines increased first and then decreased,and the expression of group ? was the highest;The relative expression of y+LAT1 and PepT1 mRNA in group ? was significantly higher than other three groups?P<0.05?;The relative expression of SLC3A1 mRNA in group ? was significantly higher than group ? and ??P<0.05?. |
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