Providing fresh pasture in the afternoon for full-time grazing dairy cows increases energy-corrected milk yield

High pasture allowance in the feed ration during the grazing season is an important resource, particularly for organic dairy farmers, as pasture intake directly affects the overall efficiency of these systems. The timing of fresh pasture provision to dairy cows could affect pasture utilisation, due to diurnal changes in herbage chemical composition and cows’ motivation to graze. This study examined the effect of time of allocation of fresh pasture on milk production and behaviour in 60 dairy cows fitted with Nedap SmartTag neck sensors. The cows were offered strip grazing with a high herbage allowance (>40 kg DM/cow/d) after either morning milking (treatment AM; n = 30) or afternoon milking (treatment PM; n = 30). Cows were milked twice daily (0500 and 1500 h) and individually received 4 kg grain-mix per day. Adaptation to treatment was implemented for two weeks, followed by five days of recordings. The PM and AM pasture offered had on average a metabolisable energy content of 12.3 and 12.1 MJ/kg dry matter, respectively, and did not differ in herbage composition. Total grazing time was longer (P < 0.001) for PM than for AM cows (576 and 520 min/cow/d, respectively). Conversely, total rumination time was shorter (P < 0.001) for PM than for AM cows (409 and 469 min/cow/d, respectively). Cows in the PM group had higher (P = 0.009) energy-corrected milk (ECM) yield than cows in the AM group (28.6 and 26.0 kg ECM/cow/d; respectively). Even though both groups were on full-time grazing, a simple change in grazing management by providing access to fresh pasture in the afternoon resulted in more time spent grazing and increased ECM yield. Taking cows’ grazing motivation into account when timing fresh pasture allocation can thus be beneficial in increasing efficiency on full-time pasture.