Annual Ryegrass Pasture for Dairy Cows Receiving Total Mixed Ration

The inclusion of herbage in the diet of medium yielding dairy cows offered a total mixed ration (TMR) may be beneficial. This study, which involved mid lactation dairy cows, examined the effect of partial replacement of a TMR with annual temperate pasture. Treatments were ad libitum TMR (TMR100), 75% ad libitum TMR + ryegrass (Lolium multiflorum ‘Maximus’) (TMR75), and 50% ad libitum TMR + ryegrass (TMR50). Twelve multiparous Holstein and F1 Jersey × Holstein cows were divided into six homogeneous groups, taking account of milk production (26.6 ± 4.5 kg/day), days in milk (128 ± 50) and body weight (546 ± 31 kg). Treatments were compared in a replicated 3×3 Latin square design, comprising three 21-day periods (measurements during final 5 days). Cows on TMR75 and TMR50 strip grazed between morning and afternoon milking (7 h/day), with a target pre- and post-grazing sward height of 24 and 12 cm, respectively. Herbage DM intake was estimated as the difference between pre- and post-grazing herbage mass. The TMR and herbage had a crude protein content of 150 and 303 g/kg DM, and a NDF content of 366 and 495 g/kg DM, respectively. Herbage DM intake increased from 4.8 kg/day in TMR75 to 6.7 kg/day on TMR50. Total DM intake decreased from 19.4 kg/day (TMR100), to 18.1 and 15.9 kg/day (TMR75 and TMR50, respectively). Milk production, milk fat and milk protein content were similar between treatments, averaging 25.6 kg/day, 44.6 g/kg and 33.7 g/kg, respectively. The net energy for lactation (NEL) supply was 113, 104 and 92% of NEL requirements, for cows receiving TMR100, TMR75 and TMR50, respectively. Ryegrass pastures were able to replace up to 50% of TMR offered to mid lactation dairy cows without any adverse effects on milk production and milk composition