The voluntary intake of oat straw by adult cattle as affected by the method of dietary presentation of a concentrated solution of urea, minerals and vitamins

Abstract

SUMMARYThree experiments were conducted to assess the effects of several methods of dietary presentation of 250 g/day of a fully soluble liquid supplement (LS) on the voluntary intake of oat straw by non-productive cows fitted with a rumen fistula (Expt 1), pregnant beef cows (Expt 2) and lactating beef cows (Expt 3). In each case the cows received fixed daily amounts of barley (2 kg for Expts 1 and 2; 3 kg for Expt 3). LS contained (g/kg) about 1100 crude protein (as urea), 30 calcium, 15 phosphorus and 50 salt plus trace elements and vitamins. In Expt 1, provision of LS in either the drinking water, or via the rumen fistula or sprayed on to the straw increased voluntary straw intake by about 12%. In Expt 2, provision of LS, whether by spraying on the straw or in a molasses lick, increased straw consumption, but giving LS in the drinking water did not. In both Expts 1 and 2 the digestibility of the oat straw was not significantly affected by the dietary supplement, any increases in metabolizable energy intake being reflexions of increased intakes. In Expt 3 there was no difference in the voluntary intake of oat straw by group-fed lactating beef cows offered LS in either the drinking water or as a molasses lick.Giving LS sprayed on the straw, or incorporating it into a molasses lick to housed animals, are convenient and practical methods of supplementing ruminant diets to increase their voluntary straw consumption. Inclusion of LS in drinking water gave inconsistent results, but the method warrants further investigation.