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 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 d) milk performance were 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
protein were estimated using the double n-alkane 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
