Performance of high producing dairy cows with three different feeding systems combining pasture and total mixed rations.

Forty-five Holsteins cows in early to mid lactation were used to compare three feeding systems combining pasture and total mixed rations (TMR) on animal performance in a 21-wk repeated-measures experiment. The three treatments were: 1) pasture plus concentrate (PC), 2) pasture plus partial TMR (pTMR), and 3) TMR (non-pasture). Total dry matter intake, using chromic oxide as a marker, was 21.6, 25.2, and 26.7 kg/d for PC, pTMR, and TMR, respectively. Milk production was highest for TMR (38.1 kg/d), lowest on PC (28.5 kg/d), and intermediate for pTMR (32.0 kg/d). Cows on pTMR and TMR had higher milk fat and true protein percentages than cows on PC. Cows on PC gained less body weight and lost more body condition compared with cows on pTMR and TMR. Initial concentrations of plasma nonesterified fatty acids were higher on PC (302 microeq/L) than on pTMR (130 microeq/L) and TMR (225 microeq/L). Plasma and milk urea nitrogen were lower on both pTMR and TMR than on PC. Combining pasture and TMR resulted in higher milk production, milk fat and protein percentage, and maintenance in body condition score compared to pasture plus concentrate. The TMR feeding system resulted in the highest total dry matter intake and milk production.