| With the improvement of sheep breeding intensive and scale,sheep production is faced with the double dilemma of continuous high market price of bulk feedstock and the shortage of forage source.So in intensive agricultural areas of China,how to reduce concentrated feeding to avoid contradiction between human and livestock for grain and how to solve the lack of feed energy due to less concentrate feeding in the large-scale sheep breeding process is the urgent problem to be solved.In addition,with high lambing rate,strong adaptability and other fine traits,as female parent,Hu sheep was introduced into Xin Jiang,Inner Mongolia and HeBei province of the northern of China,however,due to lack of winter forage,inadequate intake of nutrients phenomenon in large-scale breeding was ubiquitous.Feed energy and protein levels affect the growth performance and meat quality of sheep in fattening period,however,the energy level plays a more important role in muscle growth and fat deposition.At the same time,the energy level of the diet will affect the energy intake of the lamb,interfere with the energy metabolism of the body and affect the energy supplyment of mitochondrial oxidation,lead to the restriction of the molecular mechanism of sex hormone synthesis,and thus affect the synthesis of sex hormones,testicular development and sperm production.Therefore,in actual production,it is often tried to alleviate the premature growth retardation caused by the growth retardation in the late compensatory feeding.However,the specific compensation effect is not clear.This study aims to analyse the effects of different energy restriction and compensation on production performance,slaughter performance,organ development,serum parameters,meat quality and other indicators,meanwhile,this study objective to study the effects of energy restriction on testis development and gene expression profiles to provide theoretical reference for making reasonable compensation feeding program.The main test results are as follows:1.Effect of energy restriction and compensation on growth performance and slaughter performance of Hu sheepEighty three-month-old healthy male Hu sheep with similar weight(22.02± 0.14 kg)were selected randomly and divided as four groups:energy control group(EC),85%energy group(EG1),70%energy group(EG2)and 55 energy group(EG3).In the two months restriction period,the dietary digestion levels were 11.63,9.7,8.40 and 6.84 MJ/kg,respectively.Compensatory period of three months,the dietary digestion level was 12.44 MJ/kg.In this study,lambs were weighed every month.After two stages,four in every group,totally thirty-two lambs were slaughtered and the slaughtering performance of each carcass weight,GR value and other slaughter were measured.The results showed that with the increase of feeding limitation,the body weight and daily gain of lambs decreased significantly(P<0.05);the carcass weight and GR value have decreased trend,among them,the carcass weight and GR value of EG3 group were significantly lower than those of EC group(P<0.01);There was no significant difference in the slaughter rate between two groups(P>0.05).After the compensation,the body weight of the restricted feeding group has no significant difference(P>0.05);from EC to EG3,carcass weight has decreased trend,among them,the carcass weight in the EG3 group was significantly lower than that in the EC;the GR value increased with the energy limit of 85%energy,however,decreased with the increase of restriction(P<0.05).There was no significant difference in the slaughter rate between the two groups(P>0.05).Therefore,the 3-month compensatory growth can restore the restricted growth performance at the early stage of fattening,but will reduce the carcass weight,GR value and other slaughter performance indicators.2.Effects of energy restriction and compensation on organ development and serum indicatorsIn this experiment,after energy restriction and compensation period respectively,vein blood were taken from the jugular vein,centrifuged for serum to detect serum indicators,and then slaughtered to take the organs weighing.The results showed that:1)With the increase of feeding level,the weight propoetion of head,fur,hoof,liver,spleen,lung,kidney and pancreas had decreased trend,and the detected organs except heart in EG3 were significantly lower than EC(P<0.01),while the ratio of head,hoof,heart and pancreas weight to pre-slaughter live weight showed an upward trend,and the specific gravity of liver decreased.After the compensation,with the increase of the feeding level,only the weight of the pancreas decreased,among them,EG2 group was significantly lower than the EC,and the rest of the detection organ weight returned to control group level.Except that the pancreas ratio in EG2 group was lower than that in EC,the ratio weight of other detected organs were all recovered to control group level(P>0.05).2)After restriction feeding,rumen weight in restricted group was extremly lower than control group(P<0.01);the small intestine and large intestine weight of EG1 were significantly lower than that in EC(P<0.05);only the wrinkled stomach ratio was significantly lower than the control group(P<0.05).After compensation,only the weight ratio of valve stomach was lower than that in control group(P<0.05),the other detected digestive organs all recovered to control group level(P>0.05).3)After restriction,the GLU level in EG3 was higher than that in EG2 group(P<0.05).However,after compensation,from EC to EG3 the TP in secrum had a increased trend and the TG and CHOL concentation in blood had overall downward trend.4)After rstriction,with the increase of restricted level,the GH and Leptin concentration had a n increased trend,however the IGF-1 and T concentration had a decreased level.After compensation,GH concenration in EG2 and EG3 were higher than EC and EG1,the Leptin had an increased trend,the T concentration recovered to control group level.So,energy restriction decereased the organs weight,increased organ ratio and influnced the serum biochemical indicators and reproduction hormone.After compensation feeding,most detected organs and serum indicators recovered to normal level.3.Effects of energy restriction and compensation on the meat quality of Hu sheepAfter energy restriction and compensation,lambs were slaughtered and 300g longest muscle-like meat were taken from each lamb to detecte meat quality.The results showed that:1)After restriction feeding,with the increase of the restricted feeding level,the pH,pH24 and drip loss of longissimus dorsal all had increased trend,among them,the pH value in EG3 were significantly higher than that in EC and EC and EG2(P<0.05);the pH24 in EG3 was higher than that in EC,EG1 and EG2;the drip loss in EG3 were higher than that in EC and EG1(P<0.05).After compensation,the water loss rate showed increased trend,however,the pH,pH24,water loss rate,cooked meat rate and flesh color index L,a.b were all not influenced.2)After restriction,with the increase of restricted level,the CP content of longissimus dorsi increased(P<0.05),but the EE content was lower(P<0.05);the DM and Ash content were similar to normal level(P>0.05).After compensation the DM,CP,EE and Ash in each groups had no difference(P>0.05).3)After restriction,with the increase of restricted level,the eye muscle area and the cross-sectional area of muscle fiber showed decreased trend;among them,the eye muscle area in EG3 was significantly lower than EC,EG1 and EG2(P<0.01),the muscle fiber area in restricted group was significantly lower than that in control group(P<0.01).After compensatory feeding,the area of muscle fibers in EG2 and EG3 were higher than that in the EC and EG1;the eye muscle area and muscle fiber density in the restricted group returned to the control group level.So energy restriction will increase the ratio of dorsal muscle protein and muscle fiber density,thereby improve the meat quality.After compensating for growth,the muscle fiber density becomes larger,the water holding capacity decrease and the meat quality is relatively poor.4.Effects of energy limits on testis development and gene expression profiles of Hu SheepNutritional intake and reproductive allocation are strongly associated,and dietary energy restriction or surpluses can affect reproductive capacity.This study investigated the testes development and changes regulation in serum reproductive hormonesin response to different energy restricted feeding and compensation,using high-throughput sequencing to analyze transcriptome dynamic changes of the testes sample under energy restriction feeding.We found that only in the EG3 group testes weight,testes ratio and testosterone concentration were significantly lower than those in EC after restricted feeding,after compensation feeding,all the detected indicators recovered to control group level(P>0.05).So,the testes of EC and EG3 group were then used for further transcriptome analysis.175,771,456 and 152,109,294 reads were respectively got from two groups,and 77.63%-79.62%celan reads were mapped to genomic reference gene.Using the gene hierarchical clustering analysis,GO functional enrichment and KEGG pathway data analysis,the "molecular fuction"(GO:0003674),"biological process"(GO:0008150)and "connection"(GO:0005488)related GO enrichment were the most,and EG3 had 261 different expressed genes,among them,81 genes were upregulated and 180 genes were downregulated compared to EC.Furthermore,based on the pathway enrichment of steroidogenesis,meiotic mitosis,and proteins and kinases related to energy metabolism,we screened the genes that have roles in testicular development or reproduction for further analysis,which included downregulated genes CYP11A1,ALDH3B1,FDFT1,WNT2,PGR and upregulated gene INSR.The six genes were verified by quantitative real-time PCR which indicated the reality of transcriptome datas.This study indicated that compensation can recover or relieve the reproduction decline duo to the less energy supplyment in the early period,and from the angle of differences in gene expression profiles,the molecular mechanism influenced testicular development associated with energy-restricted feeding was explored. |
