| By collecting and sorting out the data of dry matter intake and milk yield of Holstein milking cows from 2015 to 2017 in Liangcheng county,Wulanchabu city,this paper statistically analyzed the feed conversion rates of milking cows(primary cows and intermediate cows)in different months,and drew the feed conversion curve.The seasonal change of feed conversion and lactation period of Holstein milking cows in this area were discussed.To provide reference basis for improving dairy cattle raising management and operation management.The results show that:1.Seasonal change of feed conversion rateDMI of milking cows was higher in May and October at 24.74 kg/d and 25.28 kg/d,respectively.Within the range of 24.26～25.28 kg/d,the monthly average value was 24.71 kg/d,0.12%higher than the average value in May,and 2.25%higher than the average value in October.There was no significant difference between the monthly average values of DMI(P>0.05).In the range of 35.9～32.7 kg/d,the monthly average is 33.89 kg/d.In June,the highest milk production is 35.9 kg/d,with an increase of 8.9%.In December～January,the lowest milk production is 32.7 kg/d,with the milk production in April～August above the average,and the rest months below the average,with a significant difference(P<0.05).Within the range of 1.37～1.51,the feed conversion rate in June was the highest at 1.51(%),with an increase of 5.29%,with a significant difference of(P<0.05).The feed conversion rate in November was the lowest at 1.37,with a decrease of 4.20%,with a significant difference of(P<0.05).The monthly average value is 1.43,which is above the average value of feed conversion in April to August,and below the average value in other months.It is the highest in June every year,and begins to decline in July,and the lowest in October to November.It starts to rise in December,and increases in January,February and march,and increases rapidly in April.2.Feed conversion rate changes during lactation(1)During the 16～17 weeks of lactation,the maximum value of DMI was 28.3 kg/d;during the 63～64 weeks of lactation,the minimum value was 19.1 kg/d.From the 18th week of lactation to the 30th week of lactation,the lactation level was high.During the 8th to 9th week of lactation,the milk yield of the cows was the highest at 44.2 kg/d,and the lowest at 14.9kg/d during the 59-60 week of lactation.During the 1st to 8th week of lactation,the milk yield showed an increasing trend,and during the 11th to 33rd week of lactation,the milk yield decreased significantly from the 43rd week.The feed conversion rate of lactating cows during lactation period was as high as 1.86%in the first lactation month,as low as 0.80 in the 14th lactation month,decreased by 39.24%from the first lactation month to the 10th lactation month,and significantly decreased by 29.20%from the 10th lactation month to the 14th lactation month.(2)The highest lactation level was 25.1 kg/d at week 26～27,and the lowest was 21.9 kg/d at week 73～74.The lactation level was higher from week 27 to week 43,and decreased rapidly from week 44 to 48,and then remained stable.The milk yield of the new-born cattle was the highest in week 13～14At a height of 35.3 kg/d,the lactation at 73～74 weeks was as low as 21.5kg/d,the lactation at 1～14 weeks was on the rise,and the lactation at 15～42 weeks was on the decline.From week 48,the milk production decreased significantly.During the lactation period,the average feed conversion rate of newly born cows was as high as 1.83%in the first lactation month,as low as 1.09 in the 14th lactation month,and showed a downward trend of 31.14%from the first lactation month to the 10th lactation month.There was a significant downward trend from the 10th lactation month to the 14th lactation month,with a decline of 12.70%. |
