Protein sources and starch-protein digestive dynamics manipulate growth performance in broiler chickens defined by an equilateral-triangle response surface design

Shemil P Macelline; Peter V Chrystal; Peter H Selle; Sonia Y Liu

doi:10.1016/j.aninu.2022.01.003

Protein sources and starch-protein digestive dynamics manipulate growth performance in broiler chickens defined by an equilateral-triangle response surface design

Anim Nutr. 2022 Feb 3:9:204-213. doi: 10.1016/j.aninu.2022.01.003. eCollection 2022 Jun.

Authors

Shemil P Macelline^{1

2}, Peter V Chrystal², Peter H Selle^{1

3}, Sonia Y Liu^{1

2}

Affiliations

¹ Poultry Research Foundation, The University of Sydney, Camden NSW 2570, Australia.
² School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Sydney NSW 2006, Australia.
³ Sydney School of Veterinary Science, The University of Sydney, Sydney NSW 2006, Australia.

Abstract

A total of 360 male, off-sex Ross 308 chicks were offered 10 dietary treatments from 14 to 35 d post-hatch in an equilateral-triangle response surface design feeding study in order to confirm the importance of protein and amino acid digestive dynamics in broiler chickens. The 3 apical diets were nutritionally-equivalent containing either soybean meal, non-bound amino acids or whey protein concentrate as the major source of dietary protein and amino acids. Appropriate blends of the 3 apical diets comprised the balance of 7 diets and each dietary treatment was offered to 6 replicate cages with 6 birds per cage. Growth performance, nutrient utilisation, apparent protein and starch digestibility coefficients were determined in 4 small intestinal segments. The optimal weight gain (2,085 g/bird) and feed conversion ratios (FCR, 1.397) were generated by Diet 50S50W which included a 50:50 blend of apical diets rich in whey protein concentrate and soybean meal. Broiler chickens offered Diet 50S50W also had the highest experimental and predicted jejunal digestibility (0.685 in proximal jejunum and 0.823 in distal jejunum). FCR was not correlated with apparent distal ileal digestibility coefficient (P > 0.05) of protein but was correlated with apparent protein digestibility in proximal jejunum (r = -0.369, P = 0.040) and distal jejunum (r = -0.316, P = 0.015). Surplus dietary starch was correlated with increased fat pad weight (r = 0.781, P = 0.008). The findings confirmed the relevance of protein digestion rate, reflected by jejunal digestibility, on feed conversion of broiler chickens. A balance between protein-bound and non-bound crystalline or synthetic amino acids may be required for optimal growth and protein digestion.

Keywords: Amino acid; Digestive dynamics; Glucose; Protein; Starch.