Comparisons of the starch equivalent (SE) and metabolisable energy (ME) systems in feeding cattle

Rations were formulated for dairy cows and for growing and fattening cattle by the starch equivalent (SE) and the new metabolisable energy (ME) system, to show in quantitative terms the differences that are recognised between the two systems. For a low-yielding cow, rations formulated by both systems are very similar, but for a high-yielding cow the SE system greatly underestimates energy requirement: at a production of 40 kg (8.8 gal) milk daily an extra 2 kg (4.4 lb) of a barley-soyabean concentrate is needed daily to meet the energy requirement according to the ME system. For a particular rate of gain in young newly weaned animals and in older animals gaining weight at a moderate rate on a high roughage diet, the energy level recommended by the ME system is lower than that by the SE system. The difference corresponds in each case to about 0.5 kg of a barley-soyabean concentrate daily. For older animals gaining weight rapidly on a high concentrate diet the ME system requires slightly more energy for a given weight gain, than the SE system.