Beef production: studies on feed intake and on the use of a feed additive

Abstract

The effects of a feed additive (Monensin sodium) on intake and feed efficiency. the factors affecting the accuracy of using Cr 0 as an external indicator for digestibility and intake studies ana ihe physiological aspects of compensatory growth were reviewed. In experimental work conducted by the author, Monensin was fed as a component of a cereal-based concentrate diet to ~rowing and finishing cattle under indoor fedding ··and grazing· con~itions 'in1.977 and "197a. Monensin fed to cattle on the normal winter rations depressed silage intake during the store period in 1977 and improved LWG during the 1977 finishing period and the 1978 store period. Feed efficiency was improved in all cases. The reaeone for the different modes of action ~1Cre investigate,d. When Mone'nsin was offered •. dth concentrates on good pasture in 1977 it had no effect on either intake or UIG nor did concentrate supplementation improve feed intake or LWG. In the 1978 storo per'Lod two levels of feeding each with Monensin at two levels were compared. The effect of Monensin at the two levels of feeding was not significantly different. In 1978, the effects of the preceding winter level of feeding on the intake and !MG at pasture was studied. Intake and LWG of the cattle that had been subjected to a restricted growth rate of O.5kg/day were higher on pasture than of controls Which had grown at a rate of 1.08kg/day. The reasons for this were examined. Several detaileel studies of techniques were made. Two methods of estimating faecal output, total collection or by using an external marker (c-201) were compared. The Cr20'3gave better estimates • In the 1978 gra~ing period, two faecal sam~ling techniques, field or grab sampling were compared with the grab samples taken at three different sampling time schedules. The error associated with the Cr20 concentration of the field samples was less than with grab sampfes but the correlation between the Cr20J concentration of field and grab samples was highly significant. In the 1978 finishing period, the effect of time of access to feed on intake vas studied. Increasing the time of access to grass silage from 5 to 24hr. significantly increased total feod intake.