Impact of feeding grass clover press cake silage to late lactation dairy cows on rumen fermentation parameters, nitrogen and phosphorus excretion and utilization

• Press cake silage can partially replace grass silage in the diet of dairy cows • Cows fed press cake maintained similar milk production to the grass silage group • Feeding press cake can potentially reduce the environmental impact of dairy production In the green biorefinery process, the biomass is mechanically separated into a solid and a liquid fraction. The biorefined silage obtained from this process has been shown to have potential as feed source for ruminants. However, little is known regarding the optimum level of biorefined silage in the diet of lactating dairy cows and the impact on production parameters and N and P excretion in late lactation cows. Six late lactation cows were used in a Crossover experiment consisting of 3 periods of 21-d each. Dietary treatments were offered ad libitum as TMR and were as follow: Grass-clover silage only (GS); 25% grass-clover press cake silage (PC25); 50% grass-clover press cake silage (PC50). All cows received 4 kg DM of concentrate per day. Milk production, milk composition, and rumen fermentation parameters were not affected by treatment. Milk urea (mg/100mL) was lower for cows offered the PC25 and PC50 diet compared to those offered the GS diet. Dry matter intake and N digestibility were lower in cows offered PC50 diet, N intake (kg/d) was lower, urinary N output (kg/d) was 10% lower but a higher proportion of N was excreted in feces. The PC50 diets also has a 24% lower P intake and a 19% lower fecal P (kg/d). Nitrogen use efficiency and PUE was higher for cows offered PC50. Compared to GS the PC50 diet maintains milk production and could potentially reduce the environmental impact of dairy production.