Evaluation of Sunflower Meal as a Protein Supplement for Lactating Cows

Abstract Isonitrogenous concentrate rations containing 60% of the crude protein from either soybean meal (50% crude protein) or sunflower meal (37% crude protein) were fed at 1 kg/3kg milk produced to 10 cows each during a 16-wk lactation trial. All cows received corn silage ad libitum and 2.5kg alfalfa-brome hay daily. Milk yields and composition were not affected by diet. Averages for soybean meal and sunflower meal fed cows were: milk, 21.2 and 21.1 kg/day; fat, 3.96 and 3.87%; protein, 3.44 and 3.44%; and solids-not-fat, 8.85 and 8.89%. Milk casein nitrogen, serum protein nitrogen, and nonprotein nitrogen concentrations were not affected by ration. Feed composition and changes in body weight were not affected by ration. Ruminal ammonia 3 to 4h postfeeding was slightly higher (8.62 versus 7.17mg/100ml) in sunflower meal-fed cows, possibly reflecting the greater solubility of the sunflower meal protein in the rumen. Volatile fatty acids in the rumen were not affected by ration although concentrations of several acids tended to be higher in cows fed sunflower meal. Rumen pH was lower in sunflower meal-fed cows. Protein from sunflower meal is equivalent to that from soybean for lactating cows.