Effect of Age and Sex on True Digestibility of Amino Acids of Rapeseed and Soybean Meals in Growing Broilers

Studies were conducted to evaluate the influence of age and sex of birds on true digestibilities of protein (TDP) and amino acids (TDAA) of two rapeseed meals and a soybean meal. Sixty-four broilers (50% of each sex) were used both in the first (at 3 wk of age) and the second trials (on the same animals at 6 wk of age). At the end of 3 and 6 wk of age, the birds were fasted for 24 h and then force-fed with moistened diets (diet:water: 50:50) approximately 40 and 90 g, respectively. Excreta were collected during the two 24-h periods after force-feeding. The TDP and TDAA of rapeseed and soybean meals decreased significantly as the age of broilers increased from 3 to 6 wk. At 3 wk of age, the TDP and TDAA were not influenced by the sex of the animals. At 6 wk of age, the TDAA of the two rapeseed meals was higher in males than in females. The TDAA of soybean meal did not vary with sex. Sex had no effect on the TDP values of the three raw materials tested.