Utilization of soybean oil and tallow in young turkeys compared with young chickens.

The experiment was conducted to determine the apparent metabolizable energy and apparent fatty acid digestibility of tallow and soybean oil (8% of the basal diet) in young (1 and 3 wk of age) turkeys compared with young chickens. At 1 wk of age, turkeys used fats, particularly saturated fats, more efficiently than young chickens (i.e., total fatty acid digestibility was 96.5 vs. 86.4% for soybean oil and 75.0 vs. 49.1% for tallow). This difference between the two species disappeared at 3 wk of age, when there was an increase (95.7 vs. 99.3% for soybean oil and 64.0 vs. 69.7% for tallow) in fat utilization in young chickens, whereas in turkeys it remained constant (96.5 vs. 99.3% for soybean oil and 75 vs. 69.3% for tallow). This result suggests a greater and earlier maturity of the digestive system for fat utilization in turkeys than in young chickens. This efficient utilization of saturated fatty acids in turkeys seemed to depend more on the fat origin than on bird age, because it remained constant with age (91.4 vs. 96%) when saturated fatty acids were provided by soybean oil, and decreased (particularly for C18:0: 5.08 vs. 35.8%) when saturated fatty acids were provided by tallow. In turkeys, fluctuations in secretion of bile salts or in lipase activity during the trial period may have caused the lower stearic acid digestibility at 3 wk of age. The present study revealed a difference in fat utilization between turkeys and young chickens. For higher validity of the digestibility of fats, it would be preferable to use turkeys to derive metabolizable energy and fatty acid digestibility of fat values in formulating turkey diets.