EFFECTS OF FLOURENSIA-CERNUA INGESTION ON INTAKE, DIGESTA KINETICS, AND RUMINAL FERMENTATION OF SHEEP CONSUMING TOBOSA

Tarbush (Flourensia cernua DC.) contributes substantially to the Chihu ahuan Desert shrub biomass, but is browsed sparingly by livestock. Thi s study was designed to assess nutritional benefits and/or toxicosis o f ingestion of pre-bloom tarbush leaves by sheep fed a low quality nat ive grass diet. Sixteen ruminally cannulated sheep (46 kg) housed in i ndividual pens were randomly assigned to 1 of 4 treatments for 28 days . Treatments were ground tobosa grass (Pleuraphis mutica Buckl.) subst ituted with 0, 10, 20, or 30% (dry matter basis) whole tarbush leaves (19% CP). At 20 and 30% of the diet, tarbush increased (P = 0.0049) dr y matter intake during week 3, and sheep consuming 30% tarbush tended to increase dry matter intake during week 2 (P = 0.0559). Dietary tarb ush did not affect any variable associated with ruminal fluid kinetics , particulate digesta kinetics, or in situ degradation rates of tobosa dry matter or neutral detergent fiber (P > 0.05). Molar butyrate prop ortions (P = 0.0032) and total volatile fatty acid concentrations (P = 0.0064) were greater for the 30% tarbush treatments. Ruminal ammonia was greater (P < 0.0029) at 6, 8, and 12 hours postfeeding for the 30% tarbrush treatment. Sheep lost body weight regardless of treatment; h owever, sheep not fed tarbush tended (P = 0.0945) to lose more weight. Serum clinical profiles (day 0, 7, 15, and 21) confirmed nutritional stress but did not suggest toxicosis.