EFFECTS OF FEEDING SMALL AMOUNTS OF AMMONIA TREATED STRAW ON DEGRADATION RATE AND INTAKE OF UNTREATED STRAW

Four sheep, each fitted with a rumen cannula, were fed barley straw either untreated plus urea (10 g kg-1) (Control), treated with ammonia (AS) at 35 g kg-1, or untreated plus urea supplemented with 200 g or 400 g AS (200 AS or 400 AS) in a Latin square design. The straws were supplemented with minerals and vitamin. Daily intake of untreated straw was 641, 816 and 667 g per animal on Control, 200 AS and 400 AS diets. Total straw dry matter intake was 641, 1003, 1019 and 1152 g day-1 per animal on Control, 200 AS, 400 AS and AS diets, respectively (P < 0.01). Studies on degradation rate in the rumen were carried out to provide some explanation for the changes in intake. Degradability studies using the nylon bag method showed that the rate of degradation of untreated straw was increased from 0.024 h-1 to 0.031 and 0.041 in the rumens of sheep fed 400 AS and AS diets, respectively (P < 0.05). Rumen fluid from the sheep was also used as an inoculum to ferment untreated straw in vitro. Rate of gas production was observed to be significantly higher (P < 0.05) when rumen fluid from animals fed 200 AS, 400 AS and AS diets was used to ferment the straw. The extent of degradation or total gas production was not affected by diet. Differences in straw intake were attributed to differences in degradation rate caused by the stimulatory effect in the rumen of the increased supply of fermentable energy provided by the ammonia treated straw.