Influence of age period on the total protein efficiency and energy retention rate of broiler chicks fed a conventional or an all vegetable ingredients finishing diet 76

Experiments were carried out to study the changes in the values of total protein efficiency (TPE) and energy retention (ER) of broiler chicks fed two maize-soya bean meal diets with (conventional diet) or without (vegetable diet) added meat-bone meal (100 g kg-1 diet) during five age periods (18-25, 25-32, 32-39, 39-46, and 46-53 days). Results indicated that the type of diet bad no significant (P > 0.05) effects on TPE (weight gain/protein consumption) and ER values. The average values were 2.27 for TPE and 17.2 MJ week-1 bird-1 for ER during the five age periods. The pooled relative energy retention RER (ER/energy consumption) value amounted to 0.77. No significant (P > 0.05) difference was observed in the final (53 days of age) live body weight of chicks fed a vegetable diet (2788 g bird-1) or a conventional diet (2712 g bird-1). The values of TPE decreased and ER increased with advancing age. The pooled TPE value was 2.98 during the IS-25 days of age and decreased to 1.62 during the 46-53 days of age. No significant difference was noticed in TPE values between the 25-32 and the 32-39 day age periods. The pooled RER value was 0. 76 during the 18-39 days of age and increased slightly to 0.79 during the 39-53 days of age. The ER and RER values during the five age periods were negatively correlated to the TPE values (r = -0.86 and r = -0.74, respectively). Changing from a broiler finishing diet containing animal protein by-product to another containing all vegetable ingredients bad no adverse effects on the energy retention rate and protein efficiency of broilers. However, the studied parameters were found to be influenced by the age period of broiler chicks.