Exploration On The Effects Of Different Weaning Ages On Growth And Development In Dairy Sheep Lambs

This study studied the effects of different weaning ages on the growth and development of dairy lambs,aiming to find the most suitable weaning age under the premise of normal growth and development of lambs,and it provides a scientific basis for the application of early weaning technology in dairy sheep production.In this experiment,F1 male lambs were randomly divided into four groups.The experimental groups were weaned at 7,15,and 25 days of age(EW7,EW15,EW25),and fed with milk replacer powder;the control group(CON)was fed with goat milk artificially.Then the following studies were carried out:(1)The body weight,body height and body length of lambs were measured.Part of lambs at 90 days of age were randomly selected for slaughter to analyze the effect of early weaning on slaughter performance.(2)Blood was collected at the age of 90 days to determine the physiological and biochemical indicators of blood and study the histomorphology of the gastrointestinal tract of lambs.(3)Rumen fluid and rumen materials were collected at slaughter to analyze the effects of early weaning on the rumen fermentation parameters and microorganism community of rumen.(4)IGF-1 and Ghrelin genes are related to the growth and development of whole or partial tissues,and SLC22A5 gene is equally important as carnitine transport gene.The samples of liver and abomasum were collected,and the expression of IGF-1,Ghrelin and SLC22A5 genes were analyzed.The result shows:(1)There was no significant difference in body weight and carcass weight among each group at d90(P > 0.05).Different weaning ages have no significant effects on lamb growth and slaughter performance.(2)Different weaning ages have no significant effects on normal metabolism and blood immunity of lambs.Histological analysis of digestive system showed that early weaning did not affect the development of rumen,but promoted the development of small intestine to some extent.(3)The results of rumen fermentation parameters showed that there was no significant difference in p H and microbial proteins content between EW groups and CON(P > 0.05).Early weaning did not affect the normal development of rumen microflora,but different weaning ages would affect the diversity of microflora.The species richness of EW25 group was higher than that of EW7 and EW15 groups(P <0.05).The relative abundance of most of the flora is close,but there are still deviations.The rumen bacterial diversity showed some differences between different EW days of age but no obvious effect.(4)There was no significant difference in the expression of the liver IGF-1 m RNA of the four groups of lambs(P > 0.05);early weaning increased the expression of Ghrelin and SLC22A5 genes in the abomasum and liver,indicating that early weaning promotes body energy metabolism and organ maturation and development.These results indicated that different weaning time did not significantly affect the growth and development of dairy sheep lambs.And there was no significant difference in the growth indexes between the weaning group at 7 days of age and the control group.In order to maximize the economic value,weaning at 7 days of age was recommended.