Abstract :
A study was conducted to evaluate soybean hulls (SH) as a replacement of tifton bermudagrass
hay (TH) in diets of goats containing high levels of spineless cactus. Ten mature bucks
(five ruminally fistulated) were used in a 5×5 Latin square experiment with 21-day periods.
Soybean hulls replaced 0, 250, 500, 750 and 1000 g/kg of TH in the experimental diets.
All diets contained 600 g/kg spineless cactus (dry matter basis). Intakes of dry matter (DM),
organic matter (OM) and non-fiber carbohydrates and chewing activities decreased linearly
(P < 0.01) as the level SH in the diet increased. In vivo digestibility of DM, OM and neutral
detergent fiber increased linearly (P < 0.01) as the level of SH in the diet increased. Addition
of SH linearly increased (P < 0.05) N retention without affecting microbial N supply (g/kg
of digestible OM intake) to the small intestine. Ruminal pH and NH3-N decreased linearly
(P < 0.05) while total volatile fatty acid (VFA) concentration increased linearly (P < 0.05)
as proportion of SH in diets increased. It was concluded that inclusion of SH in cactusbased
diets had a negative impact on intake and chewing activities but improved total tract
nutrient utilization by goats. Replacing TH with SH resulted in a concentrate type ruminal
fermentation (i.e., low ruminal pH and high VFA concentration).
