Cereal type and conditioning temperature altered protein and carbohydrate molecular structure, nutrient retention and performance in broilers fed pellet diets during starter and grower period.

1. Effects of cereal type and conditioning temperature (CT) on protein and carbohydrate (CHO) molecular structures, nutrient retention, carcass and blood characteristics, caecal microbial population and growth criteria of broilers fed pellet diet were evaluated for a total period of 35 d.2. In total, 336-day-old Cobb 500 broiler chicks were randomly allotted into a 2 × 2 factorial arrangement with two different cereal types (maize or wheat) processed in two different temperatures (CT; 68°C or 90°C) with seven pen replicates containing 12 birds each.3. Chicks fed the maize-based diets significantly gained higher body weight (BW) and lower feed conversion ratio (FCR) in comparison to the chicks fed wheat-based diets during the whole grow-out period (p < 0.01). Overall, the highest BW and feed intake (FI) were seen in birds fed wheat-based diets conditioned at 68°C, but the lowest FCR was observed in maize-based diet conditioned at 90°C at 7, 14 and 21 d of age (p < 0.01). However, BW was higher and FCR lower in chicks fed maize-based diets conditioned at 90°C in the grower period (28 and 35 d; p < 0.01).4. The α-helix height was higher in wheat-based starter diets in comparison to the maize-based diet (p < 0.01). Ratio of amide I to II area and total CHO peak height were increased when diets were processed at 90°C in both maize and wheat-based starter diet (p < 0.05). Increasing the CT from 68°C to 90°C reduced CHO peak 1 and 2 height by 11.6% and 3.95%, respectively, in maize-based starter diets, while increasing the CT from 68°C to 90°C reduced CHO peak 1 and 2 height by 54.3% and 57.2%, respectively, in wheat-based starter diets. In the grower diets, increasing the CT from 68°C to 90°C increased CHO peak 1 by 23% in maize-based diets, but reduced CHO peak 1 by 24.5% in wheat-based diets.5. Calcium and phosphorous retention were highest in chicks fed wheat-based diets conditioned at 90°C and lowest in chicks fed maize-based diets conditioned at 90°C (p < 0.01). Salmonella, E. coli and coliforms in the caeca reduced significantly (p < 0.05) in chicks fed wheat-based diets conditioned at 90°C on d 11 and increased with the same diet at 35 d of age compared to the chicks fed maize-based diets conditioned at both 68°C and 90°C or wheat-based diets conditioned at 68°C.6. Conditioning the wheat-based diets at 68°C improved production responses without causing any adverse effects on protein and CHO molecular structures, however increasing the conditioning temperature to 90°C impaired performance due to alteration of protein and CHO molecular structures. In contrast, conditioning of the maize-based diets at 90°C had the opposite effect, and improved production performance compared to diets conditioned at 68°C.