Relationship between dry matter intake, milk performance and energy efficiency from dairy cows offered grass-only, grass-white clover and total mixed ration feeding systems

Dry matter (DM) intake (DMI) is one of the most limiting factors for milk production in pasture-based dairy production systems. The inclusion of white clover (Trifolium repens L.) in grass swards can increase voluntary DMI through improved sward nutritive quality and lower resistance to breakdown in the rumen. Feeding a total mixed ration (TMR) can support greater milk production from increased daily DMI, and greater control of feed intake quality. The objective of this study was to determine the relationship between DMI, milk production, and energy efficiencies for dairy cows consuming different diets. The 3 treatments imposed were perennial ryegrass (PRG; Lolium perenne L.) receiving 250 kg N/ha (GRASS), PRG and white clover receiving 150 kg N/ha (CLOVER) and total mixed ration (TMR). Dry matter intake was estimated 17 times over the duration of the study (2015-2021). Simultaneously, milk production, production efficiencies, energetic efficiencies and feed quality were also measured. Significant increases in milk yield production (+ 5.0 kg), and DMI (+2.8 kg) were observed when cows consumed the TMR diet compared with the pasture-based diets. In terms of energetic efficiencies, greater energy (+2.84 unité fourragère lait (UFL)) was available for milk production after maintenance for the TMR treatment compared with GRASS and CLOVER, while the TMR and CLOVER cows required similar energy to produce 1 kg STDMY. All treatments had similar energy (148.64 g UFL) available for MS production after accounting for maintenance. Cows fed the TMR diet consumed an additional 2.30 kg DMI daily compared with the CLOVER cows. The cows grazing the CLOVER swards consumed, on average, 1.03 kg greater total DMI (TDMI) compared with the GRASS cows. This translated into greater daily milk (+1.2 kg) and MS (0.12 kg) yield compared with the GRASS treatment. At a white clover inclusion rate of 31.3 and 37.7% in July and September, respectively, the herbage NDF was significantly reduced compared with GRASS. The current study highlights the benefits of a TMR and PRG-white clover feeding systems for increasing DMI, milk production, and energy efficiencies compared with PRG-only.