The effects of forage digestibility and concentrate supplementation on the nutritive value of the diet and performance of finishing cattle

Abstract

Hays varying from 58 to 75% organic matter digestibility (OMD) were offered ad libitum to steers weighing approximately 400 kg, together with concentrates at rates varying from 0·0 to 8·5 g organic matter (OM)/kg live weight per day. Total digestible OM intake (DOMI) increased linearly by 0·75 g/g concentrate OM intake (OMI) for a hay of 58% OMD, but by only 0·26 to 0·36 g/g concentrate OMI for hays above 70% OMD. With hays above 70% OMD, supplementary feeding had little effect on the overall OMD of the diet but significantly depressed the cellulose digestibility of the diet. With the hays of lower digestibility, supplementary feeding increased the OMD of the diet by an average of 0·90% units/unit concentrate OMI, and had no significant effect on the cellulose digestibility of the diet. Live-weight gain increased with increasing digestibility of the hay and with increasing level of supplement.In multiple regression equations, variations in hay digestibility and concentrate intake accounted for from 77 to 91% of the variation in hay intake, diet digestibility and total DOM intake.