DIGESTIBILITY, NITROGEN RETENTION AND CALORIC VALUE OF RAPESEED AND SOYBEAN MEALS WHEN FED AT TWO DIETARY LEVELS TO CALVES

Abstract

Pre-pressed, solvent-extracted rapeseed and solvent-extracted soybean meals were fed with a basal diet to Holstein bull calves at levels to support maintenance or growth. Maintenance requirement was based on digestible energy (DE) = 145 W^0.75 (kg). Growth rates of 0.55 and 0.75 kg per day were supported by intakes of 1.66 and 1.92 × maintenance for rape-basal and soy-basal diets. The digestibility of proximate components and energy were determined by the "difference" procedure. The derived crude protein digestion coefficients of rapeseed and soybean meals were 89 and 93%, resulting in digestible protein contents of 35 and 47%, respectively. The gross energy digestion coefficient was lower (P < 0.01) at the maintenance level of intake than at the level for growth, for both mixed rations (81, 89 for rapeseed meal and 78, 88 for soybean meal). The mean caloric values of rapeseed and soybean meals derived by difference were 3213 and 2926 kcal DE/kg dry matter, respectively. It was concluded that rapeseed meal is lower in digestible protein content but equal to or greater in DE value than soybean meal.