Body composition and estimated tissue energy balance in Jersey and Holstein cows during early lactation

The rate and extent of estimated energy mobilization and the relationship b etween fat depth at the rib and thurl and body condition score (BCS) were i nvestigated in Jersey and Holstein cows in early lactation. Twenty-six cows were paired by breed, parity, and calving date, and were individually fed a total mixed ration ad libitum from parturition through 120 d in milk. Fee d intake and milk production were measured daily; body weight (BW), BCS, su bcutaneous fat depth, milk composition, and concentration of plasma noneste rified fatty acids were measured every 2 wk. Estimated tissue energy balanc e (TEB) was calculated using 1989 NRC equations. Net energy intake was grea ter in early lactation for Holsteins compared with Jerseys, 37.8 and 28.2 M cal/d, respectively. Milk energy was greater for Holsteins relative to Jers eys, 30.5 versus 21.2 Mcal/d. Fat depth and BCS did not differ between bree ds. A positive relationship existed between fat depth and BCS for Jerseys; however, there was no significant relationship for Holsteins. The best-fit regression model for predicting TEE for Holsteins and Jerseys in early lact ation included week of lactation, milk composition, and BCS. Jerseys remain ed in negative TEE for a shorter period of time relative to Holsteins. The TEE nadir was -6.19 and -12.9 Mcal/d, for Jerseys and Holsteins, respective ly. Expressed as a proportion of metabolic BW (BW0.75), net energy intake d id not differ between breeds, yet milk energy and estimated tissue energy l oss were greater for Holsteins compared with Jerseys.