Effects of hay inclusion on intake, in vivo nutrient utilization and ruminal fermentation of goats fed spineless cactus (Opuntia ficus-indica Mill) based diets

A study was conducted to determine the minimum level of tifton bermudagrass hay (TH) required to maximize cactus intake by buck goats without compromising nutrient utilization or ruminal fermentation. Five ruminally fistulated goats were used in a 5 x 5 Latin square experiment with 17-day periods. Experimental diets contained (g/kg dry matter (DM) basis) 765, 670, 572, 473 and 373 spineless cactus and 50, 150 250, 350, and 450 TH, respectively. Intake of DM increased quadratically (P<0.05) while intake of organic matter (OM), crude protein (CP) and neutral detergent fiber (aNDF) increased linearly (P<0.05) as the level of TH in the diet increased. However, intake of non-fiber carbohydrates (NFC) decreased quadratically (P<0.05) as a result of TH inclusion. Total tract digestibility of DM (average 0.71), OM (average 0.74), CP (average 0.80), aNDF (average 0.55) and NFC (average 0.90) were not influenced by TH level in the diet. Nitrogen retention and microbial N supply to the small intestine were similar for all dietary treatments. Hay inclusion linearly increased (P<0.05) ruminal pH and NH3-N concentration, and rumen content of DM and aNDF. Inclusion of TH in cactus based diets improved feed intake without adversely affecting in vivo nutrient utilization or ruminal fermentation and inclusion of 150 g/kg TH (DM basis) was sufficient to maximize cactus intake. (C) 2007 Elsevier B.V. All rights reserved.