| The anogenital distance in dairy cows is measured from the center of the anus to the retrolabial union or clitoris.This reproductive phenotype serves as a crucial indicator of sexual development and is closely linked to reproductive traits.This study focused on Chinese Holstein cattle from two large-scale dairy farms in the Jiangsu area.The researchers measured five body-scale traits,which included anogenital distance,cross height,rump length,rump width,and hip width.They measured a total of 2,841 cows,including 679 young cows and 2,162 lactating cows.Additionally,the researchers collected and determined information such as birth dates and lactation days of the cows.A multivariate analysis of variance was conducted to examine the impact of various factors,including farm,parity,and lactation stage on body size traits,specifically the anogenital distance of cattle.The AL-REML module in the DMU software was utilized,along with the EM algorithm and multi-trait animal model,to estimate the heritability,phenotypic correlation,and genetic correlation of several traits in Holstein cattle,including anogenital distance,cross height,rump length,rump width,and hip width.In the No.1 cattle farm,1777 cows with breeding records and calving data were sorted by the distance between anus and vulva and divided into four groups using the quartering method.A selection of cows from each group had their tail veins collected during breeding to measure levels of Anti-Mullerian hormone(AMH),Follicle stimulating hormone(FSH),and Luteinizing hormone(LH)in their plasma using the ELISA method.Reproductive performance indicators such as difficulty and age at first calving,using multi-factor analysis of variance to analyze the effects of anogenital distance and parity on reproductive hormones and reproductive performance of dairy cows;combined with Logistic regression to analyze the effects of anogenital distance on the first and first two breeding rate,retained placenta and dystocia rate.The main results are as follows:1.The anogenital distances of young cows and lactating cows were normally distributed,and the mean values were 109.96±9.17 mm and 122.59±9.62 mm,respectively.Different cattle farms and ages had significant effects on the distance between the anus and vulva,the height of the cross,the length of the rump,the width of the rump,and the width of the waist angle(P<0.05);rump length,rump width,and hip width were significantly higher than those of cattle under 18 months of age(P<0.05);the anogenital distance,cross height,rump length,rump width,and hip width of young cattle in No.2 cattle farm were significantly Higher than No.1 cattle farm(P<0.05);the anogenital distance of young cattle was significantly positively correlated with the height of the cross,the length of the rump,the width of the rump,and the width of the waist angle(P<0.05).Different parities and lactation stages had a significant effect on the anogenital distance of lactating cows(P<0.05);the anogenital distance of cows with 4 or more parities was the longest,and the anogenital distance of cows in the early lactation stage was significantly higher than that in the other three lactation stages(P<0.05);the 3rd parity cow had the longest rump length,the 1 st parity cow’s hip width was significantly lower than other parity’s(P<0.05),and the pre-lactating cow’s hip width was significantly lower than other parity’s(P<0.05).The anogenital distance of lactating cows was significantly negatively correlated with rump length,rump width and hip width(P<0.05).2.The estimated heritability values of anogenital distance,cross height,rump length,rump width and hip width are 0.24±0.06,0.30±0.11,0.25±0.07,0.21±0.07 and 0.29±0.07 respectively;the anogenital distance and There was a negative genetic correlation between hip width and rump length,and the correlation coefficients were0.243 and-0.052,respectively,and the genetic correlation coefficients with cruciate height and rump width were 0.334 and 0.317,showing a moderate positive correlation.3.Different anogenital distances between heifers and lactating cows had significant effects on the concentrations of AMH,FSH and LH during breeding(P<0.05).The concentrations of AMH and LH in plasma of young cattle in the short anogenital distance group(83.91～102.19mm)were significantly lower than those in the long group(114.94-130.99 mm)(P<0.05);The concentration of FSH was significantly higher than that of other groups(P<0.05).The plasma AMH and LH concentrations of lactating cows with short anogenital distance group(90.33～117.12mm)were significantly lower than those of shorter group(117.13～123.66mm)(P<0.05);anogenital distance was significantly lower than other groups(P<0.05).There was no significant difference in AMH,FSH and LH concentrations during mating of different parity cattle.4.Different anogenital distances of young cattle had no significant effect on the length of gestation,calf birth weight,first calving age,retained placenta rate and dystocia rate.The conception rate of the first mating and the first two mating of young cattle in the shorter anogenital distance group(102.26～108.18 mm)were significantly higher than those in the long group(114.94～130.99 mm)(P<0.05),and the conception rates were the anogenital distance group is 2.578,2.602 times of cows.The gestation period of lactating cows with short anogenital distance group(90.33～117.12 mm)was significantly longer than that of longer group(123.68～129.63 mm)and long group(129.64～157.29 mm)(P<0.05);perinatal days of lactating cows were significantly lower than the longer group(123.68～129.63 mm)and long group(129.64～157.29 mm)(P<0.05);The conception rate of the first mating and the first two mating were significantly lower than those of the long group(129.64～157.29 mm)(P<0.05),which were 0.683 and 0.656 times,respectively;the rate of conception in the first mating and the first two mating of cows with one and two fetuses was significantly lower than that of cows with four or more fetuses,and the rate of dystocia in cows with one fetus was significantly higher than that in cows with two or more fetuses.In summary,different cattle farms and ages have a significant impact on the anogenital distance of young cattle(P<0.05);different parity and lactation stages also have a significant impact on the anogenital distance of lactating cows(P<0.05);the anogenital distance.The estimated heritability was 0.24.Different anogenital distances of young cows and lactating cows had significant effects on the concentrations of AMH,FSH and LH during mating(P<0.05);different anogenital distances of dairy cows had significant effects on the conception rate of cows for the first and first two mating(P<0.05),but had no significant effect on the rate of retained placenta and dystocia rate.The results can be used as a reference for improving the reproductive level of dairy farms and the economic benefits of pastures in Jiangsu. |
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