Comparison of diets based on grass silage, hay or oat straw supplemented with four levels of concentrates in the feeding of growing Ayrshire bulls

Authors

• Ilmo Aronen Agricultural Research Centre of Finland, Institute of Animal Production, FIN-31600 Jokioinen, Finland
• Martti Lampila Agricultural Research Centre of Finland, Institute of Animal Production, FIN-31600 Jokioinen, Finland
• Helena Hepola Department of Animal Science, P.O. Box 28, FIN-00014 University of Helsinki, Finland

DOI: https://doi.org/10.23986/afsci.72684

Abstract

This experiment was conducted during three consecutive years with 144 Ayrshire bulls of an initial age of 185 days and live weight of 186kg. The experimental period lasted for 224 days. The ad libitum fed roughages were grass silage, hay and oat straw, each supplemented with four levels of concentrates, the number of treatments thus being 12. Daily supplements of concentrates were 0,1, 2 or 3 kg on grass silage feeding, 1,2, 3 or 4 kg on hay feeding and 2,3, 4 or 5 kg on straw feeding. Barley was used as a concentrate on grass silage feeding, but part of it was replaced by rapeseed meal and urea in the hay and straw feeding groups to balance the nitrogen intake. An increase in concentrate intake was found to decrease the roughage intake with each type of roughage, but the total intake of dry matter (DM) was increased. Increasing the level of concentrates enhanced both the rate of daily live weight gain (LWG) and carcass gain. However, 2 kg more concentrates was needed on hay feeding than on grass silage feeding to obtain similar carcass gain. On straw feeding, 4 kg of concentrates was not sufficient to obtain a comparable carcass gain as with grass silage alone. The response to concentrate supplementation on grass silage feeding indicated, however, that the growth potential of the bulls receiving silage alone or silage with small amounts (1 or 2 kg/day) of concentrates was not completely utilized. The study showed that LWG is an inadequate measure of animal performance when diets with different fill characteristics are compared. With coarse diets, a relatively large proportion of LWG is rumen contents. Comparisons of animal performance and feed conversion should, instead, be done in terms of carcass gain.