Relationship between dry matter intake, milk performance, and energy efficiency from dairy cows offered grass-only,...

Dry matter intake 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 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 (GR), PRG and white clover receiving 150 kg N/ha (CL), and 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 GR and CL, whereas TMR and CL cows required similar energy to produce 1 kg standard milk yield. All treatments had similar energy (148.64 g milk solids/UFL intake) available for milk solids production after accounting for maintenance. Cows fed the TMR diet consumed an additional 2.30 kg DMI daily compared with the CL cows. The cows grazing the CL swards consumed, on average, 1.03 kg greater total DMI compared with the GR cows. This translated into greater daily milk (+1.2 kg) and milk solids (0.12 kg) yield compared with the GR 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 GR. The current study highlights the benefits of a TMR and PRG-white clover feeding system for increasing DMI, milk production, and energy efficiencies compared with PRG only.