Summary

Under whole grain feeding (WGF) regimes broiler chickens are provided with a bi-phasic ration in which 25% may consist of whole grain coupled with a 75% ‘balancer’, usually a pelleted concentrate. Anecdotally, WGF regimes first met with acceptance in Europe, especially in Scandinavian countries; however, presently in Australia WGF regimes apply to the majority of broiler chickens. This acceptance of WGF is somewhat surprising because the number of reported investigations is quite limited and their interpretation is complicated by tangible differences in methodologies and objectives across the relevant studies.
It is generally accepted that WGF increases relative gizzard weights, improves feed conversion ratios (FCR), reduces mortality rates and enhances gut integrity. Any improvements in FCR are obviously advantageous and these improvements partially stem from increases in gizzard weight and function, which enhance the initiation of protein digestive processes. However, WGF has been shown to increase energy utilisation and this may be due to WGF-induced generation of more slowly digestible starch, which benefits energy utilisation and FCR. Also, WGF provides birds with the “choice” of selecting relatively high or low protein intakes, which may be advantageous.
Thus the objectives of this project are to define the positive responses generated by WGF and identify the strategies so that these positive responses may be maximised. In addition, the intention is to clarify the genesis of positive responses to WGF, which probably include the provision of slowly digestible starch, enhanced gizzard function and the ‘choice-feeding’ opportunity that WGF extends to broiler chickens.

Program

Chicken Meat

Research Organisation

The University of Sydney

Objective Summary

This project has two prime objectives. The first is to define the positive growth performance and nutrient utilisation responses promoted by WGF and to clarify the underlying mechanisms. The second, and more applied, objective is to identify the most appropriate WGF strategies including the proportion and type of whole grain to be offered.
From a preliminary review, WGF increases relative gizzard weights, improves feed conversion ratios (FCR) and reduces mortality rates. Reductions in mortality rates are advantageous and may stem from enhanced gut integrity. Improvements in FCR are more advantageous and one explanation is that increased gizzard weights and function enhance the initiation of protein digestive processes culminating in improved feed efficiency. However, the positive impacts of WGF may not stem entirely from increased gizzard weights. The first additional factor to be considered is the real possibility that WGF generates more gradually digestible starch, which benefits energy utilisation and FCR. The second is that WGF provides birds with the “choice” of selecting relatively high or low protein intakes, which may be beneficial.
Several variables merit investigation to identify the most appropriate WGF strategies. These include the most suitable cereal to feed as whole grain and proportions of whole grain to be offered during the various feeding phases. The protein content of the pelleted concentrate may be critical and is partially dependent on the proportion of whole grain being offered. The efficacy of phytases, proteases and reducing agents may be impacted by WGF but this has not been fully investigated.