Extruded blend of soybean meal and sunflower seeds for dairy cattle in early lactation.

An extruded blend of 44% crude protein soybean meal (50%), whole sunflower seeds (45%), and premix (5%) was evaluated as a protein and energy source for dairy cows in early lactation. Thirty Holstein cows (24 multiparous and 6 primiparous) were assigned to either a corn-oats-soybean meal concentrate or a concentrate where soy-sunflower blend replaced all soybean meal and portions of corn and oats. Dry matter of total mixed diets was 36% corn silage, 21% alfalfa haylage, and 43% concentrate. Yields of milk (33.6 and 33.8 kg/d) and 4% fat-corrected milk (30.9 and 30.5 kg/d) were similar, and percentages of total solids (11.92 and 11.38), fat (3.55 and 3.30), and protein (2.91 and 2.74) were lower in milk from cows fed soy-sunflower blend. Milk from cows fed soy-sunflower blend contained fewer short- and medium-chain fatty acids, more 18-carbon fatty acids, and was more unsaturated than from cows fed soybean meal. Intakes of dry matter and changes in body weight were not different among diets. Ruminal fluid pH and molar ratio of acetate to propionate were higher, and concentrations of total volatile fatty acids and ammonia were lower in cows fed soy-sunflower blend. Concentrations of essential amino acids in arterial serum, calculated mammary uptakes, and transfer efficiencies indicated more desirable amino acid balance in cows fed soy-sunflower blend. Methionine appeared to be most limiting with both diets.