Seasonal Changes In Grazing Behavior And Rumen Microbiota Of Yak And Cattle

The aim of the study was to investigate the blood physiological and biochemical indicators,grazing behavior and response strategy of microbial flora in rumen of yak and cattle,in the situation that the forage biomass and nutritional quality vary greatly in different seasons.This study will provide the scientific basis for improving yak production performance and animal production transformation efficiency.Both ten healthy yaks and cattle with similar body weight were selected.The Moonitor monitoring system was worn to test the grazing behavior in January 2019?Winter?,May 2019?Spring?and August 2019?Summer?,respectively.The Samples of forage grass,rumen fluid and blood were collected at the end of three periods for the analysis of the conventional nutrients of forage grass,physiological and biochemical indicators of blood,rumen environmental parameters and rumen microbial diversity.The following is the main results of this study:?1?With winter forages have the lowest biomass and nutritional quality,both yak and cattle spend less time for grazing,rumination?except for cattle?and rest activity,and spend more time for walking.Their grazing spatial distribution was more scattered.On the other hands,summer forages have the highest biomass and nutrient quality,the behaviors were opposite with mentioned above.In winter and spring,compared with cattle,the grazing and rumination activities were reduced in yak,while the walking activity was increased.Furthermore,the grazing spatial distribution was more dispersed and mainly distributed in steep hillsides.?2?The contents of NH₃-N,acetate,propionate and TVFA in rumen fermentation parameters of yak and cattle were significantly increased with seasonal changes?P<0.05?.However,the content in yak is significantly higher than the cattle in winter and spring?P<0.05?.?3?Yak and cattle have the highest rumen microbial abundance and diversity in summer,whereas the abundance and diversity in yak was higher than that in cattle in spring and summer.At the phylum level,Bacteroidetes,Firmicutes,Proteobacteria and Verrucomicrobia were relatively abundant in both yak and cattle,accounting for more than 85%and 80%of the total bacteria in the rumen,respectively.The relative abundance of Bacteroidetes of yak and cattle was the highest in winter,while the relative abundance of Firmicutes was the highest in summer.The relative abundance of Firmicutes in yak was significantly higher than that in cattle?P<0.05?in different periods.At the genus level,the relative abundance of Prevotella in yak and cattle increased with the decrease of forage nutrient quality,while the relative abundance of Butyrivibrio,Ruminococcus and Pseudobutyrivibrio were decreased.The abundance of Prevotella,Butyrivibrio,Ruminococcus and Pseudobutyrivibrio in yak in each period was higher than that in cattle.There was a significant difference in Prevotella,Butyrivibrio and Pseudobutyrivibrio in spring?P<0.05?,and a significant difference in Ruminococcus in winter?P<0.05?.It is found that the generation of NH₃-N,acetate,propionate and TVFA in the rumen of yak were closely related to the relative abundance of Butyrivibrio and Pseudobutyrivibrio through correlation analysis.The content of NH₃-N in cattle was correlated with the relative abundance of Pseudobutyrivibrio,Butyrivibrio and Anaeroplasma.Acetate is positively correlated with Clostridium?XVIII,Pseudobutyrivibrio and Butyrivibrio.Propionate was positively correlated with Ruminococcus,Pseudobutyrivibrio,Butyrivibrio and Anaeroplasma.?4?From winter to summer,in terms of blood physiological indicators,the number of white blood cells?WBC?,red blood cells?RBC?,hemoglobin concentration?HGB?,hematocrit?HCT?,and mean red blood cell?MCV?in yak and cattle are significant increased?P<0.05?,while the number of platelets?PLT?decreased significantly?P<0.05?.The contents of WBC,PLT,RBC,HGB and MCV in yak were significantly lower than that in cattle in different seasons?P<0.05?.In terms of serum metabolites,blood glucose?GLU?,insulin-like growth factor 1?IGF-1?,insulin-like Growth factor 2?IGF-2?and insulin?INS?increased significantly?P<0.05?in both yak and cattle.The non-esterified fatty acid?NEFA?,low density lipoprotein cholesterol?LDL-C?,high density lipoprotein cholesterol?HDL-C?and growth hormone?GH?of yak and cattle were significantly increased?P<0.05?.In winter or spring,the contents of GLU,NEFA,LDL-C and HDL-C in yak were significantly lower than that in cattle?P<0.05?,while GH,IGF-1 and IGF-2 were significantly higher than cattle?P<0.05?.In summary,with the decrease of forage biomass and nutrient quality,the grazing,rumination and resting activities was decreased in yak.Yak spent more time in walking and foraging,and its grazing spatial distribution was more dispersed.Compared with cattle,yak showed a more efficient response mode to harsh plateau environment in physiology,biochemistry and energy from rumen fermentation and microbial changes,in order to improve energy utilization efficiency to effectively deal with nutrient deficiency.