| This study used culling records of 23,990 Holstein cows from 2011 to 2021 and production performance measurements and reproduction records(including 12 indicators of longevity,milk production and reproductive traits)of 37,093 Holstein cows from 2009 to 2021 from nine large-scale dairy farms in Ningxia.Factors influencing longevity,milk production traits and calving interval(CI)were analyzed using the GLM(General linear model)procedure in SAS 9.2,and heritability,repeatability,phenotypic correlation and genetic correlation for each trait were estimated using the DMU software DMU-AI module in combination with animal models.The main results were as follows:1.The non genetic factors analyzed had a highly significant impact on longevity,milk production traits,and CI(P<0.01).The production life and herd life increase with the increase of parity,and decrease year by year with the year of birth.Cows born at the age of ≤21 months or 25-31 months for the first calving,as well as those born in spring and winter,had a longer lifespan.The daily milk yield,milk fat percentage,milk protein percentage,milk lactose percentage and somatic cell score of cows calving in autumn were better,while the milk yield of 305 days calving in winter was the highest.The daily milk yield of the third parity was the highest,the milk fat percentage of the second to fourth parity was high,the milk protein percentage slowly decreases after the second parity,the milk lactose percentage decreases with increasing parity,and the somatic cell score was the opposite.Dairy cows that calve for the first time at the age of 22-26 months had better milk production traits.The CI prolongs with increasing parity,the Cl for calving in autumn was the longest,and the CI for first calving in cows aged 22-23 months was shorter.When the milk yield at 305 days was greater than 8000 kg,the milk yield at 305 days was higher and the CI was longer.2.Descriptive statistics and genetic parameter estimation of longevity,milk production traits,and CI of Holstein cattle in Ningxia:(1)The average productive life and herd life were 1 006.51 days and 1 793.46 days,respectively,with an average CI of 403.71 days.The average daily milk yield was 34.27 kg/d,and the average values of milk fat percentage,milk protein percentage,milk lactose percentage,somatic cell score,and fat protein ratio were 3.83%,3.2 5%,4.99%,2.54,and 1.19,respectively.The average 305 days milk yield was 9.97 tons,and the average peak milk yield was 44.69 kg/d.The average 81.52 days peak milk production day was reached.(2)The heritability of single character animal models for estimated productive lifespan,herd lifespan,and CI were 0.0789,0.0756,and 0.0635,respectively,which were all low heritability traits.The repeatability model estimated that the heritability of milk production traits ranged from 0.036(fat protein ratio)to 0.217(305 days milk yield),and the repeatability ranged from 0.073(fat protein ratio)to 0.690(peak milk yield).Daily milk yield,milk protein ratio,305 days milk yield,and peak milk yield were moderate heritability traits.(3)The phenotypic and genetic correlations of each trait range from-0.3669 to 0.9789 and-0.6091 to 0.9931.In summary,this study analyzed the effects of non-genetic factors on lifespan,milk production traits,and CI of Holstein cattle,providing a theoretical basis for precision management of pasture.Genetic evaluation was conducted on lifespan,milk production traits,and CI,obtaining the genetic potential and genetic correlation of each trait,providing a reference basis for the establishment of genetic evaluation system and selection index for Holstein cattle in Ningxia. |
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