Analysis Of 305d Milk Yield And Lactation Curve Of Dairy Cows Born In Different Seasons

This paper collected milk production data of Holstein dairy cows that produced calves in Haigao from 2011 to 2016,and statistically analyzed the milk yield of calves born in different months?primiparous cows and multiparous cows?to draws their lactation curves,and calculate 305d milk yield.The effects of calving season on milk yield and lactation curve at 305 days were discussed.It provides reference for the correct evaluation and improvement of dairy cows'management level in large-scale dairy farms.The results show:1.305 days milk yield:For primiparous cows:?1?The calves were born from January to December were 9796.7,9606.0,9769.5,9740.2,9997.9,9909.5,9887.3,10000.6,10160.7,10077.0,10157.8,and 9866.6 kg,of which the highest value appears in September and the lowest value appears in February?10160.7 kg VS.9606.0 kg,P<0.05?.?2?The milk yield of calves born in different seasons?spring,summer,autumn and winter?was 9835.8,9932.4,10131.8 and 9873.1 kg respectively.The highest value appears in autumn and the lowest value appears in spring?10131.8 kg VS.9835.8 kg,P<0.05?.For multiparous cows:?1?For calves born from January to December,305d milk production were:9733.9,9836.4,9556.9,9720.2,9615.0,9515.8,9522.6,9645.9,9732.5,9931.0,10020.9,9948.8 kg,of which the highest value appears in November and the lowest value appears in June?10020.9 kg VS.9515.8 kg,P<0.05?.?2?The milk production of calves born in different seasons?spring,summer,autumn and winter?was 9630.7,9561.4,9894.8 and 10024.0 kg,respectively,and the highest value appears in winter and the lowest value appears in summer?10024.0 kg VS.9561.4 kg,P<0.05?.2.Lactation curve:?1?Regardless of primiparous cows or multiparous cows,the lactation curve of dairy cows born in different months or seasons is basically the same,but there are obvious differences among the monthly output during the first lactation,peak yield,or the month of peak yield,and the duration of milk production after the peak.?2?The lactation peaks of the Multiparous cows all appeared in the 2nd month of lactation,while the peaks of the lactation of the primiparous cows appeared in the 3rd and 4th lactation months;the duration of milk production after the peak is higher in the primiparous cows compared to Multiparous cows,and until the 10^th month of the lactation,the average monthly decline was 1.94%and 4.88%,respectively.Conclusion:?1?Regardless of primiparous cows or multiparous cows,the calving season had a significant impact on the 305d milk yield.In primiparous cows,it is highest in autumn and the lowest in spring;in multiparous cows,it is highest in winter and lowest in summer.?2?Regardless of primiparous cows or multiparous cows,the lactation curve of dairy cows was basically the same in different calving seasons.However,there was a significant seasonal variation in the amount and shape of milk production,peak yield,and lactation month,as well as the amount and shape of milk production in the first month of lactation,and there were significant differences between Primiparous cows and Multiparous cows.