|Title||Effects of Flourensia cernua ingestion on nitrogen balance of sheep consuming tobosa|
|Publication Type||Journal Article|
|Year of Publication||1996|
|Authors||King D., Fredrickson E.L., Estell R.E., Havstad K, Wallace J.D., Murray L.W.|
|Journal||Journal of Range Management|
|Keywords||alfalfa, blood chemistry, body weight, cholesterol, digestible protein, dry matter, feed intake, Flourensia, grasses, Leaves, New Mexico, nitrogen balance, nitrogen retention, Pleuraphis mutica, sheep, urea, weed palatability|
Flourensia cernua DC. (tarbush) is a deciduous shrub with potential as a high-protein forage source for livestock. Twenty-four Polypay x Rambouillet wethers housed in metabolism crates were used to evaluate tarbush as a N source for sheep fed a low quality grass diet. Treatments were 100% ground tobosa grass (Pleuraphis mutica Buckl.) or tobosa substituted with 10, 20, or 30% whole pre-bloom tarbush leaves (n = 5) or 26% ground alfalfa (n = 4, Medicago sativa L.) on a dry matter basis (dmb). Sheep were fed ad libitum for 11 days, after which feed was restricted to 1 % (dmb) of body weight for 11 days to reduce sorting and maintain uniform intake. Apparent dry matter digestibility was not improved (P = 0.2646) with tarbush or alfalfa. Fecal N was similar (P = 0.1626), but urinary N varied (P = 0.0008) among treatments. Apparent N digestibility differed (P = 0.0042) among treatments (43, 46, 50, 56, and 63% for sheep consuming 0, 10, 20, or 30% tarbush or alfalfa, respectively). All treatments resulted in similar (P = 0.1569) but negative N retentions (-2.4, -2.2, -2.8, -2.0, and -1.5 g day-1 for sheep consuming 0, 10, 20, or 30% tarbush or alfalfa, respectively). Serum clinical profiles (day 22) confirmed all sheep were nutritionally stressed, but did not indicate toxicosis. Although neither tarbush nor alfalfa N compensated for the low quality basal diet, N from 30% tarbush was utilized with similar efficiency to alfalfa N. The major impediment for using tarbush as a N source appeared to be low palatability.