Ration Digestibilities and Ruminal Characteristics in Steers Fed Sunflower Seeds with Additional Calcium

Abstract Twenty Holstein steers were in a 5-day digestion trial to evaluate use of oil-type sunflower seeds included at 10% of ration dry matter. Treatments were four total mixed rations consisting of (dry matter) 48% corn silage, 9% chopped alfalfa hay, and 43% one of four concentrate mixes: corn and soybean meal (positive control); corn, soybean meal, and 22% whole-rolled sunflower seeds (negative control); negative control plus 3.5% additional limestone; or negative control with sunflower seeds treated with 2% calcium hydroxide. Ad libitum intakes of dry matter were not different but tended to be less for steers fed additional calcium diets. Cellulose digestion was depressed, and digestibilities of neutral detergent fiber and acid detergent fiber tended to be less for negative control. Digestibilities of dry matter, organic matter, lipid, gross energy, calcium, and magnesium were not different among treatments. Concentration of propionate was elevated in ruminal fluid from steers fed sunflower seeds. Concentrations of insoluble fatty acid salts or soaps were elevated in ruminal fluid solids and feces from steers fed sunflower seeds but were not increased by additional calcium. Fatty acid profiles of ruminal fluid solids and feces were not altered by additional calcium. Digestion of fiber was depressed in steers fed diets containing sunflower seeds without additional calcium but not in steers fed additional calcium as limestone or calcium hydroxide. Improved digestion of fiber with additional calcium could not be attributed to increased formation of fatty acid soaps in the rumen.