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Digestion Rates of Starch but not Protein Vary in Common Cereal Grains Used in Broiler Diets

Published: February 25, 2021
By: S.Y. LIU 1, A. KHODDAMI 1, P.V. CHRYSTAL 2, A.F. MOSS 1 and P.H. SELLE 1. / 1 Poultry Research Foundation, School of Life and Environmental Science, The University of Sydney, Camden NSW 2570; 2 Baiada Poultry, Pendle Hill, NSW.
Both glucose and amino acids are essential for muscle protein deposition and feed conversion efficiency. Total tract nitrogen retention was reported to be influenced by protein and starch digestion in broiler chickens (Liu et al., 2013). Embracing the concept of digestive dynamics and applying it in practical diet formulation requires understanding of the variations of protein and starch digestion rates in different ingredients. This present study evaluated protein and starch digestion rates of 18 cereal grains, including sorghum (7), wheat (4), corn (2), barley (3), and triticale (2), in male broiler chickens from 21 – 28 days post-hatch. Experimental diets included the test grain and soybean meal and were formulated to be iso-energetic and iso-nitrogenous but without synthetic amino acids. Grains were hammer-milled through 4.0 mm screen before mixing and cold-pelleting. On day 28, a total of 648 Ross 308 male chicks (6 cages per treatment, 6 birds per cage) were euthanised (intra-venous injection of sodium pentobarbitone), and samples of digesta were taken from the proximal jejunum (PJ), distal jejunum (DJ), proximal ileum (PI) and distal ileum (DI) and pooled for each cage. The calculations of apparent digestibilities, mean retention time and digestion rates of protein and starch were conducted as described previously (Liu et al., 2013). There were more variations in protein digestibilities in the jejunum than ileum in broiler chickens. The CV of protein digestibilities among different ingredients were 8, 6, 2 and 2 in PJ, DJ, PI and DI, respectively; whereas the CV of starch digestibilities among different ingredients were 7, 7, 6 and 6 in PJ, DJ, PI and DI, respectively (Figure 1). There were no significant differences between protein digestion rates among the 18 cereal grains; however, the starch digestion rates varied by student t-test (P = 0.048). On average, wheat had the highest starch digestion rate (0.118 min-1), followed by barley (0.104 min-1), triticale (0.093 min-1), corn (0.087 min-1) and sorghum (0.075 min-1). The synchrony between glucose and amino acid absorption is essential for optimal feed conversion and nutrient utilisation, especially in reduced protein diets with high inclusions of crystalline amino acids. The present study showed the variations in starch digestion rates in different feed grains. Future consideration needs to take into account the differences of protein digestion rates in common protein ingredients.
AUSTRALIA - DIGESTION RATES OF STARCH BUT NOT PROTEIN VARY IN COMMON CEREAL GRAINS USED IN BROILER DIETS - Image 1
 
Liu SY, Selle PH & Cowieson AJ (2013) Animal Production Science 53: 1033-1040.
 
Abstract presented at the 30th Annual Australian Poultry Science Symposium 2019. For information on the latest edition and future events, check out https://www.apss2021.com.au/.

Liu SY, Selle PH & Cowieson AJ (2013) Animal Production Science 53: 1033-1040.

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Authors:
Dr Sonia Yun Liu
The University of Sydney
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Peter Chrystal
Baiada Poultry
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Amy Moss
The University of Sydney
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Dr. Peter Selle
The University of Sydney
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Graeme Coles
21 de marzo de 2021
In unpublished work, Rebecca Abbot has shown that in carefully controlled feeding studies with wheat, substantial variation in starch digestibility occurs due to variable levels of hindgut ferementation, with energy recovery after reverse peristalsis to the terminal ileum. Social status also conditions starch utilisation, with dominant bird overeating and wasting energy in an attempt to sequester resources, preventing their use in lower status birds.
Juarez Donzele
Universidade Federal de Viçosa - UFV
15 de marzo de 2021

Dr. Sonia Yun Liu, the variation in starch digestibility among the evaluated cereals could be partly justified based on the variation of the size, location and composition of the starch granule, as for the amylose and amylopectin fractions. The higher the proportion of amylose, the linear fraction, the lower the digestibility of starch. As for the digestibility of the protein, which I think is negatively influenced by the concentration of the non-starch polysaccharide, mainly the soluble (NSPs), what would be the possible justification for the result achieved, if the NSPs concentration varies significantly between the studied cereals? I hope that the considerations made are pertinent to the work. Thanks.

MUHAMMAD AKRAM
30 de junio de 2021
This is great information regarding digestion of starch because this is mainly source of energy for birds
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