Effects Of Dried Citrus Pulp Replacing Corn On Growth,Immunity,Meat Quality And Rumen Microbial Diversity Of Weaned Lambs

This study used weaned lambs as the research object to explore whether dried citrus pulp could replace a certain amount of corn in the lamb diet and what proportion of dried citrus pulp could be used as a substitute.It provides a theoretical basis for reducing environmental pollution,saving feed resources,reducing feeding costs,and promoting the development of meat goat breeding industry.After 7 days adaptation period,a total of 96 two-month-old weaned male Lezhi black goats?average BW 10.75±0.34 kg and age 60±5 d?were stratified by body weight and randomly divided into 4 treatments with 6 replicates of 4 lambs in each replicate.The basal diet of weaned lamb was prepared according to NRC?2007?goat nutrient requirements.On the basis of the basal diet,a certain proportion of dried citrus pulp was used to replace the corn in the diet,and the diets of each experimental group were prepared according to the principle of equal energy and protein.That is,the control group was a corn-soybean meal basal diet without citrus pulp,and the experimental group diets replaced the corn in the basal diet with 15%,30%,and 45%dried citrus pulp,respectively.After 60 days of feeding,weighed,collected blood,slaughtered and sampled,and measured related indexes.The results showed as below:?1?The replacement of corn with different proportions of citrus pulp in the diet of weaned lambs had no effect on the initial body weight,final body weight and dry matter intake of the lambs at 1-60 days?P>0.05?,however,compared with the control group,the average daily gain decreased significantly?P=0.0348?,and the feed to weight ratio increased significantly?P=0.0375?when the proportion of citrus pulp replacement of corn was 45%.?2?There was no difference in serum TP,GLU and SUN content between different proportions of citrus pulp replacing corn groups?P>0.05?.?3?The contents of serum total triglyceride,total cholesterol,low-density lipoprotein cholesterol and high-density lipoprotein cholesterol of the weaned lambs were not affected by different proportions of citrus pulp replacing corn in the diets?P>0.05?.?4?The replacement of corn with different proportions of citrus pulp in the diets of weaned lambs had no effect on serum and liver superoxide dismutase activity,malondialdehyde content and glutathione peroxidase activity?P>0.05?.?5?There was no difference in net meat percentage between weaned lambs with different proportions of citrus pulp replacing corn in the diets?P>0.05?.However,compared with the control group,carcass weight?P=0.0755?and dressing percentage?P=0.0650?showed a decreased trend when the proportion of citrus pulp replacement of corn was 45%.?6?The replacement of corn with different proportions of citrus pulp in the diets of weaned lamb had no effect on the dorsal longest muscle pH_30min,pH_24h,meat color a*and L*,cooking loss and shearing force?P>0.05?.However,when the proportion of citrus pulp replacement of corn was 30%and 45%,the b*value was significantly increased compared with the control group?P=0.0053?.?7?The replacement of corn with different proportions of citrus pulp in the diets of weaned lamb had no effect on the dorsal longest muscle moisture,crude protein,intramuscular fat and crude ash content?P>0.05?.?8?The replacement of corn with different proportions of citrus pulp in the diets of weaned lamb had no effect on the contents of dorsal longest muscle C10:0,C12:0,C14:0 C15:0,C16:0,C24:0,C14:1,C16:1,C18:1n9c,C20:1,C18:2n6c,C18:3n3,C20:3n6,C20:4n6,SFA,PUFA,MUFA,UFA and UFA/SFA?P>0.05?.However,when the proportion of citrus pulp replacement of corn was 30%and 45%,the percentage content of the C17:0?P=0.0022?and the C17:1?P=0.0003?was significantly reduced as compared to the control group,while the the content of C18:0was significantly increased?P=0.0091?when the proportion of citrus pulp replacement of corn was 45%.?9?There was no difference in the content of serum immunoglobulin A?IgA?,immunoglobulin G?IgG?and immunoglobulin M?IgM?between lambs with different proportions of citrus pulp replacing corn in the diets?P>0.05?.?10?The activity of diamine oxidase and content of interleukin-1,interleukin-6,interleukin-10 and secretory immunoglobulin A in the jejunum mucosa of the weaned lambs were not affected by different proportions of citrus pulp replacing corn in the diets?P>0.05?.However,compared with the control group,the activity of alkaline phosphatase showed an increased trend when the proportion of citrus pulp replacement of corn was 30%and 45%?P=0.0635?.?11?There were no effects on the pH,NH₃-N,butyrate,valerate and isobutyrate concentrations in the rumen of lambs with different proportions of citrus pulp replacement corn in diets?P>0.05?.However,compared with control group,the rumen acetate concentration and the ratio of acetate to propionate of the lamb?P<0.0001?increased linearly with the increase of the citrus pulp replacement proportion,while propionate?P=0.0004?and isovalerate concentration?P=0.0021?decreased linearly.?12?The replacement of corn with different proportions of citrus pulp in the diets of weaned lambs had no effect on the papilla height,papilla width,muscular thickness,rumen wall thickness and epithelial thickness of the rumen cranial ventral sac and the caudal portions of caudal ventral blind sac of the lamb?P>0.05?;The replacement of corn with different proportions of citrus pulp in the diets had no effect on the papilla height,muscular thickness,rumen wall thickness and epithelial thickness of the rumen dorsal sac?P>0.05?,but the papilla width increased linearly with the increase of the citrus pulp replacement proportion?P=0.0008?;There was no effect on the rumen caudal dorsal sac papilla height,papilla width,muscular thickness and rumen wall thickness of the weaned lambs with different proportions of citrus pulp replacing corn in the diets?P>0.05?,but the epithelial thickness increased linearly with the increase of the citrus pulp replacement proportions?P=0.0019?;The replacement of corn with different proportions of citrus pulp in the diets of weaned lambs had no effect on the ventral portions of rumen caudal ventral blind sac papilla height,rumen wall thickness and epithelial thickness of the rumen?P>0.05?,but with the increase of the proportion of citrus pulp replacement,the papilla width increased linearly?P=0.0228?,and the muscular thickness showed a linear increasing trend?P=0.0075?.?13?The replacement of corn with different proportions of citrus pulp in the diets of weaned lambs had no effects on the villus height,crypt depth,the ratio of villus height to crypt depth and the intestinal wall thickness in duodenum,crypt depth,the ratio of villus height to crypt depth and the intestinal wall thickness in jejunum,villus height,crypt depth and the ratio of villus height to crypt depth in ileum?P>0.05?.However,the height of villus in jejunum increased linearly with the increase of citrus pulp replacement proportion?P=0.0160?;The intestinal wall thickness in ileum showed a quadratic trend with the increase of citrus pulp replacement proportions?P=0.0896?,and reached the maximum at 30%citrus pulp replacement proportion.?14?The replacement of corn with different proportions of citrus pulp in the diets of weaned lambs increased the number of OTUs and the Shannon,Ace as well as Chao index in the rumen microbes.At the phylum level,Firmicutes and Bacteroides were the predominant phylums in rumen.The replacement of corn with different proportions of citrus pulp in the diet of weaned lamb had no effect on the relative abundance of lamb rumen Firmicutes,Bacteroides,Tenericutes,Spirochaetae,Proteobacteria,Saccharibacteria,Synergistetes,Verrucomicrobia and Chloroflexi?P>0.05?.However,compared with the control group,the citrus pulp replacing corn had a tendency to decrease the relative abundance of Actinobacteria?P=0.0659?.In addition,at the genus level,Prevotella and Olsenella were the predominant genus in control group,Prevotella1and Bacteroidales_BS11-gut were the predominant genus in 15%citrus pulp replacement of corn group,Prevotella and Bacteroidales_S24-7 were the predominant genus in 30%and 45%citrus pulp replacement of corn group.The replacement of corn with different proportions of citrus pulp in the diets of weaned lambs had a tendency to reduce the relative abundance of Olsenella?P=0.0611?and Prevotella₇?P=0.0557?.However,citrus pulp replacement of corn in the lamb diets increased the relative abundance of Lachnospiraceae_NK3A20?P=0.0237?,and had a tendency to increase the relative abundances of Christenaceae_R-7?P=0.0627?,Ruminococcacea-e_NK4A214)?P=0.0922?,Veillonellaceae_UCG-001?P=0.0815?and Treponema₂?P=0.0943?.In addition,compared with the control group,15%citrus pulp replacement of corn had a tendency to increase the relative abundance of Prevotellaceae_UCG-001?P=0.0843?.?15?Compared with the control group,15%citrus pulp replaced corn increased lambs daily profit,while 30%and 45%citrus pulp replaced corn reduced daily profit,which had a negative impact on economic benefit.The results showed that it was feasible to replace corn with 15%dried citrus pulp in the diet of weaned lambs.However,a high replacement proportion?in particular45%?would have a negative effect on the growth performance,meat quality and economic benefit of lambs.Moreover,the replacement of corn with dried citrus pulp increased the richness and diversity of the rumen bacteria,which also affected the rumen fermentation and improved the intestinal morphology and rumen development of the lambs.