Effect of Feeding Lucerne and a Mixed Diet of Oats and Berseem Clover as a Source of Fresh Forage on Ruminal Characteristics and Nitrogen Use Efficiency in Dairy Cows during the Winter Period

The inclusion of fresh forages into dairy cows’ diets during the winter can represent economic and nutritional benefits but can affect cows’ metabolic function. The study aimed to evaluate the effect of using fresh berseem clover/oat (MIX), fresh lucerne (LEG) and hay/silage (CON) as forage basis for total mixed ration during the winter period on dairy cows’ rumen characteristics and N metabolism. Three non-lactating rumen-cannulated cows were allocated to each diet for a 14-day period in a 3 × 3 Latin Square design. Sample collection occurred on the last 3 days of each period. Rumen fluid samples were analysed for pH, volatile fatty acids and N-ammonium contents. In situ forage nutrients degradability were evaluated by ruminal incubation. Serum, urine and faecal samples were collected and analysed for N content. Cows had similar feed intakes. No major changes were observed in rumen characteristics, but LEG led to greater ruminal N-ammonium and ammonium ureic N contents. Fresh pasture diets reduced the daily urine ureic N. The fresh forages improved the ruminal kinetics of dry matter and crude protein. The forage nutrients’ effective degradability was greater for the fresh pasture diets than for CON. Overall, inclusion of fresh forages had minor effects on ruminal parameters, but the use of the MIX diet represents a suitable option in terms of N use efficiency.