| Abstrakt: |
A respiration calorimetry and metabolism study was conducted to evaluate the effects of adding a commercially produced protected tallow product (PT) containing approximately 40% ether extract to a beef cattle roughate diet. Twelve yearling steers (average weight 300 kg) were fed three dietary treatments: (1) control (C), 69% alfalfa hay and 31% corn; (2) medium fat (MF), 75% alfalfa hay and 25% PT, and (3) high fat (HF), 62.5% alfalfa hay and 37.5% PT. Dry matter digestibilities for the fat-treated diets were lower (P<.05) than that for the C diet (69.6, 65.0 and 66.8 for C, MF and HF, respectively) because of an apparent decrease in the digestibility of the neutral detergent solubles fraction. Apparent ether extract digestibilities were high (85% or higher) for the fat-supplemented diets, while digestibilities of other nutrients, including neutral detergent fiber, were not influenced significantly by dietary fat. Methane energy as a percentage of gross energy was reduced by fat treatment (P<.01), probably because of a decrease in fermentable substrate rather than an inhibition of fermentation. The amount of energy retained as body fat was not increased as a result of either fat treatment. The lack of response in composition of gain may have been associated with the size and age of the animals used in the experiment. Experimentally derived net energy values for the PT were 3.4 Meal NEm/kg and 2.2 Meal NEg/kg. |
