Effect Of Temperature And Humidity Index On Milk Performance And Its Evaluation Model In Chinese Holstan In Wuhan

A total of 45,108 DHI(Dairy Herd Improvement)records about Holstein cows from three dairy farms in Wuhan from 2014 to 2018 were analyzed in this study.The 8 indicator s of dairy performance were daily milk yield,milk protein percentage,milk fat percentage,lactose,somatic cell score,milk urea nitrogen content,fat protein ratio and total solid were investigated.By using T test,one-way ANOVA and regression analysis,the all indicator observations were combined with different dairy farms in the same year.Next the indicator s were visualized,and then the indicator observations were dealt with different years in the same month.By using the SPSS regression curve fitting function,regression models were established in two ways.They were using all observations and the monthly average of observations.The best models were found from Linear,Quadratic,Compound,Growth,Logarithmic,Cubic,S,Exponential,inverse,Power,Logistic in SPSS between indicator s and THI(temperature and humidity index)and the optimal THI range for the indicator s were found.The results were follows:(1)The regression models of daily milk,milk fat percentage,somatic cell score and total solid were established.The corresponding decision coefficients were 0.115,0.146,0.103,0.278,and the regression models of the other four indicators were not established.The optimal regression model of Nissan milk was exponential model,the optimal regression model of milk fat rate was exponential model,the optimal regression model of somatic cell score was S model,and the total solid optimal regression model was quadratic model.(2)According to the best regression model,when the THI was lower than 45 or higher than 70,the daily milk yield and the total solid decreased rapidly.Milk fat percentage had been decreasing with the increase of THI.Milk protein rate,milk urea nitrogen,lactose and fat protein ratio were not found the suitable THI range.When the THI was lower than 50 or higher than 70,the somatic cell score increased slowly.In summary,it was found that:(1)THI affected daily milk yield,somatic cell score,total solid and milk fat percentage,but had no effect on milk protein rate,milk urea nitroge n,lactose and fat protein ratio;(2)The suitable THI for dairy farming was 45?70 in Wuhan.