Evaluation of Sunflower Crop Residue in Rations for Growing Holstein Heifers

Sunflower crop residue, a mixture of stalks and heads, contained 65.4% dry matter, and dry matter was 6.1% crude protein, 66.9% neutral detergent fiber, 56.6% acid detergent fiber, 15.7% lignin, and 12.6% total ash. In vitro dry matter and cell wall digestibilities were 40.6 and 31.4%. Sixteen Holstein heifers (mean weight 247 kg) were assigned to one of four rations containing 0, 8, 16, or 32% sunflower residue (dry matter). Mid-bloom alfalfa hay and a grain mixture (corn, soybean meal, dicalcium phosphate, vitamins A, D, and E) were 30 and 20% of dry matter with corn silage providing the remaining dry matter. Weight gains during a 70-d trial were 1.31, 1.18, .91, and .98 kg/d for 0, 8, 16, and 32% sunflower residue. Dry matter digestibilities decreased with increased sunflower residue in the ration. Ruminal propionate (mol/100 mol total volatile fatty acids) decreased with increasing sunflower residue, resulting in higher acetate-to-propionate ratios. Total volatile fatty acids, ruminal pH, and ammonia concentrations were not different among diets. With proper supplementation, sunflower crop residue was an acceptable roughage up to 32% of total ration dry matter for growing Holstein heifers.