The nutritional value to farm livestock of low bushel weight wheat

Abstract

Bushel weight is a measure of grain density which is affected by the level of filling of the grain, by grain morphology and by grain dry matter. Variations in bushel weight due to level of filling are reflected in changes in chemical composition. Bushel weight is used as the international standard for the trading of wheat, and also for the assessment of 'quality' at the point of entry to both flour and animal feed mills. The relationship between bushel weight and the composition of wheat is variable, with bushel weight being related closest to cell wall and starch and poorest to protein, soluble non-starch polysaccharides and oil.

There is no clear picture of the relationship between bushel weight and energy value for pigs and poultry, though it is generally recognised that poultry are sensitive to non-starch polysaccharides (NSP). Thus, if low bushel weight wheats also contain elevated levels of NSP giving rise to problems with digesta viscosity, reduced energy value to poultry might occur. Bushel weight was not found to be a good predictor of the nutritive value of wheat. However, determination of an alternative reliable predictor will require substantial commitment and investment.

It is apparent from the literature that the relationship between the chemical composition of wheat and its quality is not simple. The key components which contribute to variation in nutritive value in wheat, over a wide range of bushel weight, should be determined. Areas which should be investigated include viscosity, amino acid availability, and bushel weight determined on ground material. Rapid and accurate prediction of feed value should then be feasible at the point of entry of wheat to the feed mill and payments by compounders to producers should then reflect true variations in the nutritional quality of wheat.

4. With the aid of yield mapping combines, it is possible to envisage simple but powerful experiments which would throw light on interactions between soil variability and husbandry practices, to the greater benefit of all forms of agronomy.

5. When fields are sub-divided into multiple units, the complexity of decision-making will be considerable, and farmers will need information and decision support systems to guide them and help them manage the information. Such systems will need to analyse and display spatial data (yield maps, soil maps, sensed information) and apply decision rules to guide the farmer towards action. Given the complexity and consequent uncertainties of some of the issues, the main purpose of such systems may be to visualise the main zones, present the variable information clearly, and suggest (rather than automatically dictate) responses. These systems will also need to turn the decisions into instructions for variable applications.