Effect of Birth Season on Holstein Lactation Performance in Tianjin Area
The objective of this study was to investigate the impact of birth season on milk performance in dairy cows.The 128 346 DHI measurements were collected from 9 515 dairy cows in Tianjin between 2020 and 2023,these data included birth date,daily milk yield,milk fat percentage,milk protein percentage,and 305-day milk yield.The effects of different birth seasons,birth orders,fields and birth years on lactation performance were analyzed using the general linear model of SPSS22.0 software.Wood models were employed to fit lactation curves for different birth seasons and parities,taking the birth season as the independent variable,the parameters obtained from the lactation curve fitting were used to calculate the secondary parameters:the peak day of lactation,peak milk yield,and lactation persistence as the dependent variables,while single-factor analysis of variance was used to assess the impact of birth season on milk performance.Birth seasons,different parity,birth season × parity interaction had significant effects on lactation performance(P＜0.01).Calves born during winter exhibited significantly higher milk yield at one and two parities compared to calves born during other seasons(P＜0.05).Calves born during summer showed higher average milk fat percentage and average milk protein percentage than those born in other seasons at various parity levels,these differences were significant at second parity onwards(P＜0.05).Furthermore,calves born during winter had significantly higher 305-day milk yield and adult equivalent compared to other seasons(P＜0.05),while autumn-born calves at second and third parities demonstrated significantly higher values for these parameters compared to corresponding parities in other seasons(P＜0.05).Autumn cows displayed an earlier peak lactation day across different parities with the highest peak volume observed among those with two or more parities.Birth season,parity level,birth field,the interaction effect between birth season and parity level had a highly significant influence on milk performance of Holstein cattle in Tianjin area.The 305 days milk yield of autumn-born calves after 2,3 births were the highest,their milk peak day came earliest and the peak milk yield were highest.
国家科技期刊平台
NSTL
万方数据
