| This paper investigated the patterns of midwifery rate and birth weight in the Holstein cows.Data included from 31,047 parturitions from 2012 through 2018 for the HG dairy and selected data of calves for herds(282 ± 15 days)and single pregnancy Holstein cows which was 12618 heifers and 18429 cows.Calves were divided into the infers group and the cow’s group.The infers group was divided into,respectively,8 stages(25≤BW<30;30≤BW<35;35≤BW<40;40≤BW≤45;45≤BW<50;50≤BW<55;55≤BW<60;60≤BW),according to the calf birth weight(BW,kg)and will discuss the distribution law of calf birth weight and the effect on the cow’s assisted birth rate distribution.Another group was divided into 10 stages(268≤GP≤270;271≤GP≤273;274≤GP≤276;277≤GP≤279;280≤GP≤282;283≤GP≤285;286 ≤ GP ≤ 288;289 ≤ GP≤291;292 ≤ GP ≤ 294;295 ≤ GP≤296),respectively,according to the calf gestation length.Those discussed the relationship between calves’ gestation length and midwifery rate in Holstein.As the results show that:(1)The average birth weight of the heifer ’s group is 39.5 kg:male calves are 42.3 kg,female calves are 38.9 kg.The average birth weight of the cow’s group is 43.69 kg:male calves are 45.5 kg,female calves are 42.0 kg.The birth weight of male calves is heavier than female calves in heifers group,and the discrepancy within 3.0 kg～4.0 kg.The birth weight of cows group is heavier than the infers group with the discrepancy between 3.0 kg～4.0 kg.(2)The calves’ birth weight in the infers group has 8 stages which are the proportion of stage of calves,respectively,1,42%、10.93%、38.6%、35.81%、10.96%、2.01%、0.24%、0.04%.The distribution’s rate of birth weight between 30 kg～50 kg is 74.41%,however,the main distribution of birth weight in the region between 35 kg～45 kg,which rate is 74.41%.Another cows group has also 8 stages,respectively,0.61%、3.20%、17.09%、36.32%、27.34%、12.44%、2.56%、0.44%.The distribution’s rate of birth weight between 30 kg～60 kg is 98.95%,however,the main distribution of birth weight in the region between 35 kg-55 kg,which rate is 83.31%.(3)The average of midwifery in infers group is 8.3 5%,with 7 stages which start from 30 kg,respectively,5.59%、4.57%、5.63%、8.26%、16.63%、34.25%、53.33%.When calf birth weight heavier than 40 kg,the midwifery is significantly increasing(P<0.05),particularly soaring in the stages which are heavier than 45 kg.The average of midwifery in cows group is 4.96%,and there are 8 stages,respectively,8.04%、3.39%、3.56%、4.24%、5.08%、6.41%、13.16%、29.27%.When calf birth weight bigger than 40 kg,the midwifery is significantly increasing(P<0.05),particularly increasing in the stages which are heavier than 55 kg.In the infers group and the cows group,when the calf’s birth weight by the cow’s birth weight is heavier than 7.22%and 7.15%,the midwifery is significantly increasing.In conclusion,when calf’s birth weight in Holstein cows are heavier than 45 kg in the infers group,and 55 kg in the cows group,the midwifery is increasing severity.Using the distribution of birth weight and the midwifery rate of corresponding cows to can decline the midwifery rate to control day-yield nutrition. |
