Factors affecting the nutritive value of wheat for poultry

Abstract

In the United Kingdom the importance of wheat as an ingredient in diets for poultry, where it can supply up to 80% of the metabolisable energy and 40% of the amino acid requirements, cannot be understated. This study set out to examine the effects of agronomy on those components of wheat which make important contributions to the nutrition of poultry. Particular attention was directed at factors which were considered likely to affect metabolisable energy.

It was shown that neither the level of irrigation nor the location of the cultivation site had a significant effect on the nutrient content of wheat or its value to birds. Application of nitrogen fertilisers, however, increased the total nitrogen, true protein nitrogen and total amino acid contents. The concentrations of the essential amino acids, cysteine, methionine, lysine and threonine, were all significantly improved by levels of fertiliser addition up to 350 kg nitrogen/ha. The application of fungicide during growth reduced the ash content but decreased the total amino acid content, threonine being the essential amino acid most adversely affected.

The varieties Alexandria, Apollo, Avalon, Galahad, Mandate, Mercia, Mission, Sperber and Tonic were consistently shown to have the most desirable amino acid profiles. Sperber also tended to have a high gross energy which was well metabolised by adult birds. In contrast the varieties, Brock, Hornet, Rendezvous and Riband had rather poorer amino acid profiles, although Hornet's metabolisable energy content was relatively high, as was that of Slepjner. Amino acid digestibility coefficients appeared to be unaffected by wheat variety or site of growth, but those for the essential amino acids tended to be low, the value for lysine (81.1%) being particularly poor.

Dry matter was shown to be the single most important piece of information to use in adjusting the metabolisable energy value of wheat. Strong correlations were established between wheat density and metabolisable energy, but, because of differences between years of harvest, it was not possible to derive a prediction equation based on density for general use.