The voluntary intake of food by sheep and cattle in relation to their energy requirements for maintenance

Abstract

The voluntary intake and apparent digestibility of three roughages, alone and in mixtures, by six steers and six sheep were studied in 56 individual experiments. The fasting metabolism of each animal was also determined so that maintenance energy needs could be assessed. No significant differences between the voluntary intakes of roughages by cattle and sheep were found when, for all experiments with each species, voluntary intake (g./kg.W 0·73 )was regressed on apparent digestibility. Cattle, however, digested the same roughage better than did sheep and consumed more of it. Despite their higher maintenance needs/kg. W 0·73 , when given the same roughage cattle thus attained the same relative feeding level (energy apparently digested/energy required for maintenance) as did sheep, there being an indication that sheep were more efficient users of low quality roughages than cattle. Sheep with high maintenance requirements tended to eat more than those with low ones, but no such relationship could be established with cattle. When fixed amounts of higher quality roughage were given to both steers and sheep which were also given a lower quality roughage ad libitum , the total intake of food was in proportion to the voluntary intakes attained when the roughages were given separately.