Experiments at DRC have demonstrated birdsfoot trefoil (Lotus corniculatus) increases milk yield and milk protein concentra-tion of grazing dairy cows. An experiment was conducted in March 1998 to determine what proportion of the increased milk yield and milk protein% was due to the condensed tannins (CT) in Lotus, and what proportion was due to factors typically associated with legumes (increased herbage intake and improved forage quality). Twenty Friesian cows were housed and fed twice daily on either perennial ryegrass or Lotus for 10 days. Five cows on each diet were also drenched with 1.2 l of 50% polyethylene glycol (PEG) three times per day. PEG blocks the action of CT, preventing them binding to plant proteins. Milk yields (l/cow/d) were higher on Lotus (16.5) than on Lotus+PEG (13.8), ryegrass (10.2) or ryegrass+PEG (9.9) indicating that CT contributed to 42% of the increased milk yield that resulted from feeding Lotus rather than ryegrass. CT had no effect on intake, since intakes (kgDM/cow/d) of cows fed Lotus (16.8) and Lotus+PEG (16.7) were similar and higher than for cows fed either ryegrass (14.7) or ryegrass+PEG (13.7). CT, however, accounted for all of the increase in herbage conversion efficiency as indicated by the higher efficiencies (ml FCM/MJ ME) of cows fed Lotus (147) compared with those fed Lotus+PEG (126), ryegrass (123) or ryegrass+PEG (127). CT accounted for 57% of the increase in milk protein% as cows fed Lotus (3.61) had higher protein% than those fed Lotus+PEG (3.44), ryegrass (3.31) or ryegrass+PEG (3.30). Herbage or CT had no effect, however, on the casein or whey protein concentrations. CT had no effect on either milk fat or lactose concentration but cows fed Lotus had lower concentrations than cows fed ryegrass (P<0.05). Overall the trial showed legumes containing CT have potential as a forage for dairy cows.
Proceedings of the New Zealand Society of Animal Production, Volume 59, , 152-155, 1999
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