A study was carried out to investigate the potential of condensed tannins (CT) from sainfoin to minimize ruminal ammonia load in dairy cows grazing pasture with a high crude protein content (227 g/kg dry matter [DM]). Eight ruminally fistulated Holstein cows were supplemented daily with either 4 kg DM of dehydrated-pelleted sainfoin (CT content: 71 g/kg DM) or 4 kg DM of dehydrated-pelleted alfalfa (n = 4). Supplements were divided into two meals fed in the morning and in the afternoon before cows went on pasture. After adaptation to the diet (9 days) milk performance was measured on three consecutive days and ruminal fluid and blood were sampled on two consecutive days at 6:30, 8:00 and 16:30 h. Grass intake on pasture and the proportion of digested crude protein were estimated using the n-alkane marker technique. The supplements were consumed completely. Grass DM intake was similar for treatments (P > 0.05). Ruminal ammonia concentration increased in both treatment groups after the morning feeding (P < 0.001) but was lower (P < 0.05) for cows on sainfoin treatment than for cows on alfalfa treatment. The same trend was observed for plasma urea concentration (P = 0.06). Milk performance did not (P > 0.05) differ between treatments. In conclusion, about 25 % of sainfoin in the diet can decrease ruminal ammonia and plasma urea concentrations to a certain extent. However, to achieve a greater decrease sainfoin with a higher CT content has to be fed.
Sainfoin versus alfalfaas supplements for grazing cows