| The effects of season,parity,calving difficulty,body condition and other factors on the fecundity of dairy cows were studied,and the application effects of pre synchronization and double synchronization techniques,breeding timing,chorionic gonadotropin and other techniques to improve the fecundity of dairy cows were studied.The main results are as follows:1.The fecundity indexes of 8934 cows in summer,autumn and winter were statistically analyzed.The results showed that the conception rate,heat detection rate and 21 days pregnancy rate of cattle in summer were lower than those in autumn and winter,indicating that high temperature and heat stress in summer significantly affected the fecundity of cattle.There were significant differences in conception rate(P = 0.031)and heat detection rate(P =0.024)among the three seasons,and extremely significant differences in 21 days pregnancy rate(P < 0.01).The pregnancy rate and 21 days pregnancy rate were the highest in winter,and the heat detection rate of estrus was the highest in autumn.2.The results showed that the fecundity of 2928 cattle with one fetus,2694 cattle with two fetuses and 3312 cattle with three or more fetuses was different.The analysis showed that there was significant difference in the conception rate of the parity in estrus(P < 0.05),which was 54.37%,48.98% and 41.70% respectively.The difference of estrus identification rate was very significant(P = 0.005),and there was no significant difference between the first and second calves(75.17% and 72.25%,respectively).The estrus detection rate of the third calves was low(68.42%);The difference of 21 days pregnancy rate among parity was very significant(P < 0.01),which was 40.42%,34.83% and 27.42% respectively.3.The conception rate of dystocia cows was lower than that of natural cows.According to the midwifery situation,the delivery of 8934 cows were classified as 1(natural labor),2(relatively natural labor),3(mild dystocia)and 4(dystocia).The conception rates were49.61%,43.15%,42.04% and 33.03% respectively.4.The body BCS of cattle during breeding affects the pregnant rate of cows.The BCS score of 3382 cattle bred from November 27,2020 to February 18,2021 was used to calculate the conception rate of estrous period.The BCS score was 3.25,and the conception rate of cattle was the highest,with an average of 56.20%;The BCS of 3.5 cattle was lower than that of 49.32%.The BCS of 3.75 cattle was the lowest(41.50%).There was significant difference among the three groups(P < 0.01).5.The conception rate of 379 cows with pre-synchronous treatment and 555 cows with double synchronous treatment was 48.75% and 56.25%.The two groups was significant(P =0.04),indicating that the effect of double synchronous treatment was better than that of pre synchronous treatment.6.The effects of two breeding systems on conception rate were compared.System 1:breeder observe heat all day,and 5080 oestrus cows were bred after 12 hours;System 2: every morning to expose estrus and breeding on the spot,a total of 4365.33 days later,the pregnancy rate,oestrus identification rate and 21 days pregnancy rate of the two systems were statistically analyzed.It was found that there was no significant difference in the pregnancy rate,heat detection rate and 21 days pregnancy rate between the two systems(P > 0.05).7.Intramuscular injection of h CG significantly increased the conception rate 5days after mating.Compared with untreated cows,the conception rate during estrous period increased by 9.55%,with significant difference between the two groups(P = 0.02).The results showed that heat stress,body condition and dystocia would affect the cattle fecundity.The use of double synchronous treatment,intramuscular injection of h CG 5 days after mating and improved mating system could effectively improve the cattle fecundity.The results of this study provide a reference for strengthening and improving the reproductive management of dairy cows. |
PDF Full Text Request