Evaluation of high protein oat forage for dairy cattle.

Spear, a high protein oat variety, was evaluated during 2 consecutive yr for yields of forage dry matter and for feeding value as a silage to heifers, steers, and lactating cows. In yr 1 and 2, Spear yielded 7% and 13% less forage dry matter per hectare than Burnett, a comparative oat variety. Crude protein contents in silages were similar for varieties both years. In yr 1, Holstein heifers fed high protein and medium protein oat silages gained the same amount of weight but less weight than heifers fed alfalfa-brome hay. In a total collection digestion trial with six lactating cows, digestibilities of Spear were less than Burnett oat silage or alfalfa-brome hay. In yr 2, Spear and Burnett silages were fed ad libitum without a concentrate mixture to seven Holstein heifers each. Average daily gains were higher with Spear than Burnett. Apparent digestibilities as determined with steers tended to be less for Spear than Burnett. Dry matter intakes, milk yield, and composition were similar in a switchback lactation trial with ten cows fed spear or Burnett in oat silage supplemented with a concentrate at 1 kg per 3 kg milk produced.