FORAGE SELECTION BY RANGE SHEEP ON A BUFFELGRASS (CENCHRUS-CILIARIS) PASTURE

During 1989, six esophageally fistulated male lambs (Pelibuey X Rambou illet), weighing 38.8 +/- 1.8 kg, were used to collect monthly extrusa on a buffelgrass (Cenchrus ciliaris) dominated pasture. Sampling peri ods (January through December) lasted 9 days (5 days adaptation follow ed by 4 days for extrusa collection). Monthly extrusa were separated i n two portions; one was subjected to micro histological analysis and t he other to chemical analysis. Botanical composition of the study area (10 ha) was measured monthly. Preference indices of lambs for forage species were also determined. Vegetation of the covered area was compo sed of 71.7%, 27.7% and 0.6% grasses, shrubs and forbs, respectively, Plant contribution of grasses, shrubs and forbs to the annual diets av eraged 85.2%, 14.0% and 0.8%, respectively, Major shrubs in diets were soap brush (Porlieria angustifolia), black brush (Acacia rigidula), p ale verde (Cercidium macrum) and cenizo (Leucophyllum texanum). Soap b rush was the main preferred shrub by lambs throughout the year. Prefer ence indices for forbs were inconsistent. Buffelgrass was preferred by lambs during all months, comprising 85.1% of the annual diets. This s tudy suggested that the presence of shrubs and forbs in diets of lambs increased the levels of crude protein and in vitro organic matter dig estibility. Even though cell wall constituents (neutral detergent fibe r and acid detergent fiber) in forage selected by lambs were variable (P < 0.05) among months, percentages of these fractions were in agreem ent with published values. Mixed palatable native shrubs and forbs wit h buffelgrass in the pasture could improve the nutritive value of the dry matter available in the forage.