Effects of Flourensia cernua ingestion on intake, digesta kinetics, and ruminal fermentation of sheep consuming tobosa

Tarbush <i>(Flourensia cernua </i>DC.) contributes substantially to the Chihuahuan Desert shrub biomass, but is browsed sparingly by livestock. This study was designed to assess nutritional benefits and/or toxicosis of ingestion of pre-bloom tarbush leaves by sheep fed a low quality native grass diet Sixteen ruminally cannulated sheep (46 kg) housed in individual pens were randomly assigned to 1 of 4 treatments for 28 days. Treatments were ground tobosa grass <i>(Pleuraphis mutica </i>Buckl.) substituted 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) dry matter intake during week 3, and sheep consuming 30% tarbush tended to increase dry matter intake during week 2 (P = 0^.0559). Dietary tarbush 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>^.05). Molar butyrate proportions <i>(P </i>- 0^.0032) and total volatile fatty acid concentrations <i>(P = </i>^.0064) were greater for the 30% tarbush treatments. Ruminal ammonia was greater (P<^.0029) at 6,8, and 12 hours postfeeding for the 30% tarbrush treatment. Sheep lost body weight regardless of treatment; however, 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.