The effect of sucrose addition on intake of a tropical grass hay by sheep

Abstract

Increasing levels of sucrose (15, 30, 45, and 60% of the total dry matter intake, DMI) were added to a Control diet of a tropical grass hay (pangola grass, Digitaria eriantha) to examine the effect on DMI and digestible organic matter intake (DOMI). A pelleted lucerne (Medicago sativa) diet provided a positive Control diet with a higher metabolisable energy intake. There were positive linear and quadratic effects of sucrose addition on DMI and DOMI, reflecting increasing values from Control to 45% sucrose, which then decreased for 60% sucrose. Intake values at 45% sucrose were equivalent to 49% (DMI) and 60% (DOMI) of those shown by animals fed on pelleted lucerne. At the same time there was a decrease in hay intake and neutral detergent fibre digestibility. Rumen concentration of butyric acid increased with sucrose addition. Eating pattern changed with increasing sucrose inclusion in that meals extended over the whole day rather than most food being consumed within 5 h as occurred with the high roughage diet. Intake of sucrose was similar for all diets by 5 h, but by 24 h high sucrose diets had resulted in a higher intake of sucrose. It was suggested that the underlying characteristics of the neutral detergent fibre present in the diet regulate intake by posing a limit, which cannot be overridden.