An assessment by in vivo methods of grain quality for ruminants

For the purpose of this review, grain quality refers to the efficiency with which a grain supports growth in cattle fed diets which contain grain as a major component. Grains are fed as concentrated sources of energy. Their q uality depends on the energy content of the grain, the amount eaten, and th e efficiency, both of extraction of nutrients from the diet and of conversi on of nutrients to weight gain. This paper briefly describes the fermentati ve and digestive processes involved in releasing energy from grain and in e nsuring an adequate supply of other essential nutrients to the animal. Meth ods are then described for measuring net energy storage, nutrient release i n various sections of the tract, and storage of energy and protein both dir ectly and indirectly in studies of growth. It is recommended that in vivo a ssessment of the energy content of grains for ruminants be conducted in sta ges. Digestibility in the whole tract should be used to rank a range of gra ins, then comparisons made between grains using growth studies. Discrepanci es arising from these assessments should then be investigated using more de tailed measurements, particularly starch digestion in the stomach and intes tines.