Effect of monensin, avoparcin and grass supplementation on utilization of urea-treated rice straw by sheep and goats

Abstract

The experiment of 80-day duration investigated effects of supplementing 5% urea-treated rice straw (ad libitum) plus concentrate (35 g/kg M 0.75/day) with grass (3% of body weight (BW) on a fresh matter basis), monensin (25 ppm) and/or avoparcin (30 ppm) on digestibility, voluntary intake and BW of sheep and goats. All the diets were offered to 48 ram lambs (8/treatment), and diets, except those containing avoparcin, were fed to 16 goats (4/treatment). Animals were housed individually in pens with wooden slatted floors. Mean apparent digestibility of nutrients was higher for goats than sheep, but mean voluntary intake of DM and digestible nutrients and also, average daily gain (ADG) and feed conversion efficiency (FCE) were higher for sheep than goats. Due to the poor quality of the grass relative to that of the basal diet, no improvement ( p > 0.05) was noted when it was supplemented with grass. For sheep, although no significant effect of monensin or avoparcin on digestibility was detected, monensin gave slightly better digestibility results. Though not significant monensin caused decreased feed intake and increased ADG. In contrast when avoparcin was fed there was a significant decrease in feed intake and lower ADG. Both growth promoters resulted in slight improvements in FCE by sheep. For goats, there was no effect ( p > 0.05) of monensin on digestibility, intake nor BW. It was concluded that diets based on urea-treated rice straw supplemented with grass and/or monensin were utilized more efficiently by sheep than goats.