The relevance of starch and protein digestive dynamics on broiler performance: A Meta-analysis

Although nutrient digestibility (dig) is traditionally assessed in the distal ileum, the majority of starch and protein digestion and absorption occurs in the jejunum. Increasing attention has been directed toward the synchronization of starch and protein and their impact on growth performance and feed efficiency. The objective of this meta-analysis is to validate the relevance of starch and protein digestive dynamics on growth performance and to evaluate the validity of jejunal dig of nutrients as the indicator for digestion rate. A total of 260 data points extracted from 32 published papers were included in the analysis, covering a wide range of broiler ages and dietary compositions. A multiple-level meta-analysis was employed, which accounts for both between-study and within-study variations. The results indicate that the nutrient dig exhibits greater variation in the proximal jejunum (PJ) compared to more distal sections of the intestine. Both ileal and jejunal dig of starch and protein impacted on body weight gain (BWG) and feed conversion ratio (FCR). When ileal digestible nutrients are not limiting, optimizing proximal jejunal starch and distal jejunal protein dig would benefit BWG and FCR. Synchrony of starch and protein utilisation is essential for BWG where the maximal BWG is predicted to be 1703 g/bird when the ratio of digestible starch and protein in the PJ equals to 4.01. In conclusion, when digestion rate data is difficult to generate, proximal jejunal digestible starch and distal digestible protein can be reliable indicators of the rate of digestion to predict growth performance in broiler chickens.