THE INFLUENCE OF DIGESTIBLE ENERGY CONCENTRATION OF THE DIET ON FEED-INTAKE AND RATE OF GAIN BY BEEF STEERS

Eighty Hereford steers were fed diets with different levels of protected tallow. One-half of the steers received all-concentrate diets with 0-20% tallow, and the other half received 50% concentrate and 50% cubed alfalfa hay diets with 0-10% tallow. As the level of protected tallow in the diet increased, daily feed intake declined in both diets, but daily digestible energy (DE) intake declined then increased with the all-concentrate diets but increased then declined with the hay-concentrate diets. Digestible energy required per unit gain was not affected with the all-concentrate diets but increased then declined as the level of protected tallow was increased with the hay-concentrate diets. Carcass measurements were not influenced by the level of protected tallow in the all-concentrate diets. Carcass backfat declined with an increase in level of protected tallow in the hay-concentrate diets. Blood plasma nonesterified fatty acid levels increased as the level of protected tallow in the diet increased. Packed cell volume increased as protected tallow in the diet increased in the steers fed all-concentrate but not in those fed hay-concentrate. Blood glucose level was not affected by level of protected tallow in the diet.