Whole grain feeding: Methodologies and effects on performance, digestive tract development and nutrient utilisation of poultry

There is growing interest world-wide on the feeding of whole grains to broilers a means of lowering feed costs and because of the reported positive effects on digestive function. When finely ground, pelleted diets are fed, enlargement of proventriculus and atrophy of gizzard are observed and there is mounting evidence that these adverse effects can be effectively overcome by whole grain feeding. Whole grain feeding is also attractive as it meets the consumer demand for natural feeding in animal production systems. In addition, there is evidence that whole grain feeding may positively influence gut microflora ecology and incidence of coccidiosis. These beneficial effects have been attributed largely to the influence of whole grain feeding on the development and functionality of the gizzard. However, published data on the effects of whole grain feeding on performance of broilers are contradictory due to a number of confounding factors, including differences in experimental methodology, inclusion level of whole grain, type and quality of grain, age of birds, and feeding regime. Most published data are based on whole wheat and data on other grains are scarce. In view of absence of a comprehensive review on this important aspect in poultry nutrition, available literature on the influence of whole grain feeding on the performance, digestive tract development, intestinal microflora and nutrient utilisation are reviewed. The main factors responsible for the variable responses reported with whole grain feeding are also highlighted.