Relevance of National Research Council feed composition tables in Alberta

The nutrient concentrations of selected Alberta-grown whole barley grain (Hordeum vulgare L.), three pure hays of alfalfa (Medicago sativa L.), barley, oat (Avea sativa L.), and four pure crop silages of alfalfa, barley, corn (Zea mays L.), and oat were determined and compared with nutrient concentrations of similar forages and a cereal grain reported in the National Research Council (NRC 1984 and 1989) feed nutrient composition tables. In addition, the variations in nutrient concentrations within the selected Alberta feedstuffs were assessed as an indication of whether the feedstuffs should be analysed frequently for certain nutrients. The concentrations of zinc and copper in barley grain cultivated in Alberta were 248% and 60% of the NRC values, respectively. The phosphorus, manganese, sulphur, magnesium, CP, selenium and calcium concentrations in barley hay were 17, 18, 18, 22, 32, 50 and 100% higher than NRC values. However, the concentrations of Cu and Zn were only 18 and 40% of the NRC values. Data from the present study suggest that Alberta hays, silages and barley grain are different in nutrient concentrations from similar grain and forages reported by the NRC (1984, 1989). Due to a high percentage of Alberta feeds being below the suggested NRC requirement levels of the various trace minerals, use of NRC table values for Cu, Mn, Mg and Zn for barley hay, silage and grain, oat hay and silage, alfalfa hay and silage and corn silage could result in deficiencies of these trace minerals in beef and dairy cattle with possible adverse effects on productivity. Thus, there is a need to use Alberta-derived nutrient composition values for these elements in diet formulations for cattle in Alberta. The high CVs calculated for most of the nutrients in the selected Alberta feeds suggest that these feeds should be analysed more often in order to minimise costs of production due to nutrient shortfalls or excesses in diets formulated using nutrient values without the knowledge of variability in feed composition.