Effect of apparent metabolizable energy and sex on predictive models for growth performance, carcass traits, gut characteristics, and pellet quality in broiler chicks

This study aimed to investigate the effects of different dietary apparent metabolizable energy (AMEn) levels and bird sex on prediction models for growth performance, carcass traits, gut characteristics, and physical pellet quality (PPQ) of starter and finisher diets in broiler chicks over a 43-d period. A total of 700 Hubbard Flex feather-sexed broiler chicks were randomly assigned to 10 treatment groups (five replicates with 14 birds/replicate) within a completely randomized design across three feeding phases: starter (1 to 14 days), grower (15 to 28 days), and finisher (29 to 43 days). Diets were arranged factorially (5 × 2) with five levels of AMEn (2850, 2950, 3050, 3150, and 3250 kcal/kg), and two sexes (male and female). The results indicated a significant interaction between dietary AMEn and sex for growth performance, carcass traits, and gut characteristics, except for carcass yield, abdominal fat pad (AFP), and the relative weight of liver and leg (P < 0.05). In both sexes, birds fed diets containing 3050 kcal/kg AMEn across the starter, grower, and finisher phases showed the best growth performance from day 1 to 42 compared to other treatments (P < 0.05). Additionally, providing broilers with dietary AMEn levels higher than 3050 kcal/kg did not result in significant improvements in growth performance and carcass yield. Dietary AMEn significantly affected carcass yield, and sex had a significant impact on AFP at day 43 (P < 0.05). Birds receiving 2850 kcal/kg diets had the lowest carcass yield, whereas female broilers showed a higher AFP than males (P < 0.05). Dietary AMEn significantly influenced the pellet durability index (PDI) of finisher feeds (P < 0.05), with the 3050 kcal/kg diet exhibiting the highest PDI among all treatments (P < 0.05). In conclusion, increasing dietary AMEn levels beyond 3050 kcal/kg did not lead to linear improvements in growth performance, carcass traits, gut organ weights, and pellet quality in both male and female broiler chickens.