When Should Lactating Dairy Cows Reach Positive Energy Balance?

Abstract

Abstract A survey of the literature was conducted to ascertain when cows would typically return to positive energy balance ( EB ) and to identify factors related to the amount of time to reach positive EB. In 90% of the cases (44 out of 49 treatments), cows reached positive energy balance by 63 d postpartum. On average, positive energy balance was reached at 45 DIM. The correlation between peak milk yield or days to peak milk yield and time to reach positive EB was extremely low and not significant. The correlation between days to positive EB and energy density of the diet (r = -0.57) was significant. Additionally, individual cow data from a recent research trial were examined. Weekly means for NE l intake ( NEI ), fat-corrected milk ( FCM ) yield, and EB for 24 primiparous and 49 multiparous cows from 2 through 21 wk postpartum were used to examine the relationships between EB and FCM yield or NEI. Average time to reach positive EB was the same for multiparous and primiparous cows, 5 ± 2 wk. Positive EB had been reached by 7 wk pospartum for 92% of the primiparous cows and 73% of the multiparous cows. Energy balance was more closely related to NEI (r = 0.58) than to FCM yield (r = -0.26). There was a significant relationship between time to reach positive EB and mean daily FCM yield or NEI during the first 21 wk postpartum, but the correlation coefficients were low, 0.25 and 0.26. There was no strong evidence to suggest that increased milk yield increased time to positive EB.