Study On The Effects Of Low Altitude House-feeding On The Growth Performance,Blood Biochemistry And Rumen Microbes Of Yak And Cattle-yak

Traditionally grazing yak and cattle-yak fed in low-altitude houses can avoid the lack of forage in the cold season on the plateau,and relieve the loading pressure of livestock on natural grassland.Meanwhile,it provides a suitable environment for the growth and development of the cattle,and improves feeding economic efficiency.This experiment was conducted in the Hongyuan Yak Science and Technology Park of Sichuan Academy of Grassland Science.5 healthy Maiwa yaks and 5 cattle-yak（local cattle×Maiwa yak）males with similar weight and 36 months old were selected in the experiment.The trial was divided into two phases.The first phase was house feeding at the high-altitude（altitude:3,500 m）of the experimental yak（HY group,162.30±13.70 kg）and cattle-yak（HC group,129.60±21.06 kg）in the Hongyuan Yak Science and Technology Park,and the duration was30 days.At this stage,on the 30th day of the experiment,the cattle growth performance was measured,and blood and rumen fluid samples were collected.In the second phase of the experiment,the experimental yak（LY group,171.00±15.70 kg）and cattle-yak（LC group,142.60±26.18 kg）were transferred to the Guanghan agricultural area（altitude:480 m）,after a 30-day pre-feeding period,the experimental cattle were fed in low-altitude houses for 120days.In this phase,the second measurement of the growth performance of yaks and cattle-yaks was carried out on the 150th day of the test.After collection of blood and rumen fluid samples,a unified slaughter test of yaks and cattle-yaks was conducted to collect meat samples.During the experiment,the composition and ratio of the ration for the yak and cattle-yak were the same at all phases.The purpose of this research was to investigate the effect of low-altitude housing on the growth and development,slaughter performance,meat quality and blood biochemistry of Maiwa yak and Cattle-yak,and the structure and characteristic of the rumen microflora.The main research results are as follows:1.During the test period,except that the average daily gain of the low-altitude yak group（LC group）was significantly higher than that of the low-altitude yak group（LY group）（P<0.05）,there was no significant difference between the final weight,carcass weight,net meat weight,slaughter rate and net meat rate between the LY group and the LC group（P>0.05）.In terms of eating quality,there was no significant difference in water,ash,protein and fat content between the LC group and the LY group（P>0.05）.The longissimus dorsi muscle pH_1h,brightness（L*）,and shear force value of the LY group were slightly greater than those of the LC group,the redness（a*）,yellowness（b*）,intramuscular fat and inosinic acid content of the longissimus Dorsi muscle in the LY group were slightly lower than those in the LC group,there were no significant differences in pH,a*,b*,L*,shear force,intramuscular fat and inosinic acid content between the two groups（P>0.05）.2.The contents of savory amino acids（FAA）,total amino acids（TAA）,essential amino acids（EAA）and non-essential amino acids（NEAA）in the LY group were slightly lower than those in the LC group.The content of savory amino acids tyrosine（TYR）and phenylalanine（PHE）in the longissimus Dorsi muscle of the LY group was not significantly different from that of the LC group（P>0.05）,the content of glutamic acid（GLU）and glycine（GLY）in the LY group was slightly lower than that in the LC group,but there was no significant difference.There was no significant difference between the LY group’s amino acid indexes and the LC group（P>0.05）.3.After the test,the levels of blood glucose（GLU）,fatty acid synthase（FAS）and Acetyl-Co A carboxylase（AACase）activity in the LY group were significantly lower than those in the HY group（P<0.05）.The content of the above indicators in the LC group was also significantly lower than that in the HC group（P<0.05）.In addition,the level ofβ-hydroxybutyric acid（β-HB）,triglycerides（TG）,hormone sensitive lipase（HSL）and carnitine acyltransferase 1（CACT1）in the LY group were also significantly lower than those in the HY group（P<0.05）.The levels ofβ-HB,TG,CACT1 and lipoprotein lipase（LPL）in the LC group were significantly lower than those in the HC group（P<0.05）.4.The content of ammonia nitrogen（NH₃-N）in the rumen fluid of the high-altitude yak group（HY group）was significantly higher than that of the high-altitude catle-yak group（HC group;P<0.05）.The content of propionic acid in the LY group was significantly lower than that in the LC group（P<0.05）.The contents of NH₃-N,acetic acid and total volatile fatty acids（TVFA）in the HY group were significantly lower than those in the LY group（P<0.05）.The contents of NH₃-N,TVFA,acetic acid and propionic acid in the HC group were significantly lower than those in the LC group（P<0.05）.5.After conducting 16S r RNA by high-throughput sequencing analysis on the rumen fluid microorganisms of yak and cattle-yak,a total of 663,545 valid sequences were obtained,and 33,177 sequences were retained for each sample on average.The average length of these sequences is 292 bp and belongs to 3,069 Operational Rumen Units（OTU）.After the test,the HY group and the LY group obtained 2,762 and 2,856 OTUs respectively.The HC group and the LC group obtained 2,817 and 2,807 OTUs respectively.Comparing the two breeds of cattle,the Maiwa yak has 59 unique OTUs and the Cattle-yak has 54unique OTUs.6.At the phylum level,in the microbial flora of the rumen fluid of the test cattle,among them,Bacteroidetes（>40%of the total sequence）and Firmicutes（>30%of the total sequence）are the dominant bacteria phyla of test yak and cattle-yak.The abundance of Bacteroidetes in the LC group was significantly higher than that in the HC group（P<0.05）.Except for Bacteroidetes and Euryarchaeota,the phyla with a relatively high average relative abundance（>1%）shows a decreased trend in relative abundance as the altitude decreases.In the same housing environment,the abundance level of Eubacterium group and Fretibacterium in the HC group were significantly higher than those in the HY group（P<0.05）.For the same breed of cattle,the abundance of Prevotella＿1,Treponema＿2 and Ruminococcus＿2 in the HY group was significantly higher than that in the LY group（P<0.05）.The abundance of Escherichia-Shigella and Fretibacterium in the HC group was greater than that in the LC group（P<0.05）.7.Correlation analysis between rumen fermentation parameters and dominant rumen fluid flora at the genus level can be obtained,Christensenellaceae R-7 group has a significant positive correlation with pH（P<0.05）.Ruminococcaceae NK4A214 group has a significant negative correlation with propionic acid（P<0.05）,and Christensenellaceae R-7group has a significant negative correlation with butyrate（P<0.05）.In summary,the low-altitude house-fed cattle-yak has better growth and weight gain performance than the low-altitude house-fed yak.Compared with high-altitude house-feeding,the yak’s rumen microbial diversity increased after low-altitude house feeding.This study explores the effect of low-altitude house feeding in different places on the growth and development,meat quality and blood biochemistry of yak and cattle-yak,It enriched the information of rumen microbes under different treatments of yak and cattle-yak.It provide data support for further research on the interaction mechanism between low-altitude house feeding of yak and cattle-yak and rumen microbes.