| The aims of this study were to explore the population pattern of Chinese Holstein cattle activity and its influencing factors,to provide reference for fine management and modeling of activity in cattle,to estimate the genetic parameters of activity and related indexes,and to provide useful information for exploring genetic mechanism of activity related characters in Chinese Holstein cattle.The study used intelligent collar system to continuously monitor and collect data on dairy cows in one scaled farm in Beijing from May 2015 to June 2020.The data included the original activity of 1612 milking cows（every 2 h）and daily activity,the oestrus index of 2074 lactating cows and the activity peak of704 lactating cows（from July 2017 to May 2020）,production data,and the environmental temperature and humidity in the barn.The main findings are as follows:The effects of parity,test season,body condition score（BCS）,lactation stage,test year and device type on activity and related traits were analyzed by linear mixed model.The results showed that the original activity was 43.01au/2h,daily activity was 520.96au/d,estrus index was 71.77au,activity peak was 105.94au/2h in Chinese Holstein cattle.Activity behavior is the second most common behavior in dairy cows,next to rest.The activity of dairy cows was lowest from 00:00-06:00,and increased with the increase of temperature and humidity index.Parity,test season,BCS,lactation stage,test year and device type all had significant effects on daily activity（P<0.01）.Among the different parities,the daily activity of cows in the second parity was lower than that in the first parity.Among different test seasons,the daily activity was the lowest in winter and the highest in summer.After calving,the daily activity of cows decreased gradually as the lactation stage proceed,and decreased with the increase of BCS.Cows had the highest estrus index in the 4th estrous cycle and the lowest in the first estrous cycle,with a difference of 2.34au,while cows had the highest estrus index in winter and the lowest in summer.The activity peak of first party cows was the highest and that of third lactation was the lowest,with a difference of 3.59 au/2h.Between different estrous cycles,the highest activity peak occurred in the 2nd,the lowest in the 3rd;The activity peak was the highest in the winter,the lowest in the summer,with a the difference being 10.38 au/2h.The estimated heritability of original activity was 0.05±0.01 and the repeatability was 0.19,indicating original activity is a lowly inheritable trait.The heritability of daily activity was 0.11±0.02 and the repeatability was 0.41,indicating daily activity is a moderately inheritable trait.The heritability of daily milk yield was 0.38±0.04,and the repeatability was 0.58,indicating daily milk yield is a moderately inheritable trait.The genetic correlation between daily activity and daily milk yield was low（0.04）.The bivariate model was used to estimate the genetic parameters of estrus index and activity peak.The results showed that the heritability of the estrus index and activity peak were0.04±0.01 and 0.19±0.04,respectively,being lowly to moderately inheritable traits.The genetic correlation between the estrus index and the activity peak was 0.45±0.03.The approximate genetic correlation between the estrus index and the interval between the first and last inseminations of mature cows,the age of the first calving and the interval between the first and last inseminations of heifers were 0.37,-0.41 and-0.55,respectively.Taking the deregression proof（DRP）as the response variable and combining with the genomic information,GWAS was employed to mine the related genetic markers of the estrus index.We detected7 SNP loci significant at the whole genome level,which were located on 7 differernt chromosomes, and 31 genes were found around the significant loci（within 300 kb）,among which PTGS1 and NDUFA8 were related to the number of embryos produced by the donor,and VEGFA was related to bovine follicular development and luteal formation.In summary,this is the first study to derive the population genetic parameters of activity and its related traits（estrus index and activity peak）in Chinese Holstein cattle,related genes were also screened.Our results can provide a theoretical basis for the genetic selection of activity and its related traits in dairy cattle.The estrus index and activity peak provided novel traits in studying the estrus behavior as well as genetically improving female fertility. |
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