Effects of isoacids, urea and sulfur on ruminal fermentation in sheep fed pineapple tops

Abstract

Eight Tabasco rams were used in a 2 3 factorial crossover experiment conducted in two 4 × 4 quasi-Latin squares to study effects of supplementary isoacids, urea and sulfur on ruminal fermentation of pineapple tops. ‘Isoacids’ (ISO) refers to an equal-weight mixture of isobutyrate, 2-methylbutyrate, isovalerate and valerate. Treatments in g kg BW −1 day −1 were: ISO, 0.07 and 0.14; urea, 0 and 0.43; sulfur (S), 0 and 0.086. After each weekly experimental period, the rate of ruminal acetate production was taken as a measure of ruminal fermentation. There was significant interaction only between ISO and S. Acetate production ranged from 0.17 to 0.44 mol h −1 per sheep for the eight treatment combinations. Acetate was increased ( P < 0.05) by 0.17 mol h −1 per sheep, or 81%, when ISO were fed at the high level in diets supplemented with S. When S was added to diets containing a high level of ISO, acetate production increased ( P < 0.01) by 0.14 mol h −1 per sheep, or 56%. When urea was added to high ISO and S, acetate production was 33% higher (0.33 vs. 0.44 mol h −1 per sheep). Optimum N:S ratio was 5:1, and this apparently was more important than absolute concentration of rumen ammonia. Ruminal fermentation of pineapple tops appears to be improved by supplementing the diet with 0.14 g ISO, 0.43 g urea and 0.086 g S per kg BW of sheep.