Dietary starch to lipid ratios influence growth performance, nutrient utilisation and carcass traits in broiler chickens offered diets with different energy densities.

Ali Khoddami,Sonia Yun Liu,Peter H Selle,Peter V Chrystal,Cristina Óvilo

doi:10.1371/journal.pone.0205272

Abstract

Twelve experimental diets with three levels of energy densities (11.25, 12.38 and 13.50 MJ/kg) and fours levels of starch to lipid ratios (14:1, 12:1, 7:1, 4:1) were offered to 288 male Ross 308 broiler chickens. All the diets were formulated to contain consistent digestible lysine to metabolisable energy ratios (0.87 g digestible lysine/MJ AMEn) and ideal amino acid ratios. Growth performance was monitored from 7 to 27 days post-hatch and parameters of nutrient utilisation (AME, AMEn, AME:GE ratios, N retention) were determined from 24 to 26 days post-hatch. Apparent protein (N) and starch digestibility coefficients, carcass yield and composition were determined at 27 days post-hatch. There were no interactions between energy densities and starch to lipid ratios on growth performance and carcass weights (P > 0.05). Feed intake was reduced with increased energy densities (P < 0.001). Weight gain and FCR were improved with increased dietary energy densities (P < 0.0001). Starch to lipid ratios linearly increased weight gain (r = 0.448, P = 0.001) and feed intake (r = 0.509, P < 0.001) without influencing FCR (P > 0.75). Both nutrient densities and starch to lipid ratios significantly impacted on carcass weight and yield. Heavier carcass weights and higher yields were observed in broiler chickens offered diets with high nutrient density (P ≤ 0.001). Carcass weight (r = 0.441, P < 0.005) was positively correlated with starch to lipid ratios and this tended to be the case for carcass yield (r = 0.277, P = 0.057) too. However, there were interactions on lipid concentrations in carcass (P < 0.001) as broiler chickens offered diet containing the lowest nutrient density and the highest starch to lipid ratio had the highest lipid carcass concentration of 12.94%. In conclusion, protein and energy need to be considered in tandem in practical diet formulation, especially in diets containing high crystalline amino acid inclusions. The impact of lipid on feed intake and starch on carcass lipid concentrations should also be taken into consideration.

Highlights

The influence of protein and energy on growth performance and carcass traits in broiler chickens have been intensively studied in the literature and the investigation is ongoing because the performance of modern broiler chickens improve every couple of years as a result of successfully selective breeding program
The average weight gain and feed conversion ratios (FCR) for all the experimental treatments from 7 to 27 days post-hatch was 1591 g/bird and 1.407, respectively, which were clearly superior to the 2014 Ross 308 performance objectives of 1292 g/bird weight gain with and FCR of 1.463
Feed intake was reduced by 6.4% with increased energy densities (2314 versus 2167 g/bird, P < 0.001) and weight gain and FCR were improved with increased dietary energy densities by 10.5% (1511 versus 1670 g/bird) and 15.3% (1.533 versus 1.298), respectively (P < 0.001)

Summary

Introduction

The influence of protein and energy on growth performance and carcass traits in broiler chickens have been intensively studied in the literature and the investigation is ongoing because the performance of modern broiler chickens improve every couple of years as a result of successfully selective breeding program. Starch and lipid are the two major source of energy in typical broiler diets and little information about the influence of starch and lipid on bird performance and nutrient utilisation has gained in the literature. Liu et al [1] reported a significant 8.8% reduction in feed intake in birds offered diets containing higher lipid concentrations and such responses are often seen in practice. This could be due to dietary lipid negatively impacting on pellet quality [2], and/or delaying gastric emptying [3]. The influence of dietary starch to lipid ratios on growth performance, carcass compositions and nutrient utilization was investigated

Methods

Results

Conclusion