INTAKE AND DIGESTION OF UREA-TREATED, UREA-SUPPLEMENTED AND UNTREATED RICE STRAW BY GOATS

The intake and digestion by goats of urea-treated rice straw and untreated straws given alone or supplemented with urea were measured in a Latin square design study. Intake was measured when the straws were offered ad libitum. Digestibility and nitrogen (N) balance of the diets were measured at 85% of the ad libitum intake. Organic matter intake (45.2 g kg-1 W0.75) and digestibility (578 g kg-1) of the total diet were higher for urea-treated straw than for supplemented straw (39.4; 534) or straw alone (41.1; 527). Urea supplementation of untreated straw had no significant effect on intake or digestibility. Rumen ammonia levels were similar in goats fed on urea-treated (42.7 mg l-1) and urea-supplemented (39.7 mg l-1) straw, and were much higher than those in goats fed on untreated straw (25.7 mg l-1). The positive response to urea-treated straw was thought to be due to its higher N content in the presence of higher digestible energy. The urea treatment apparently caused a change in the physical and chemical structure of the straw, resulting in increased digestible organic matter intake, whereas urea added to the diet immediately before it was consumed did not affect intake or digestibility.