NUTRIENT INTAKE OF RANGE SHEEP ON A BUFFELGRASS (CENCHRUS-CILIARIS) PASTURE

This study was conducted to estimate and compare the organic matter (O M), energy and mineral intakes of grazing lambs in a buffelgrass pastu re during 1 year. Vegetation in the study area (10 ha) consisted mainl y of buffelgrass (70% of covered area) and shrubs such as blackbrush ( Acacia rigidula), pale verde (Cercidium macrum) and cenizo (Leucophyll um texanum), Shrubs comprised about 27% of the covered area. From Janu ary through December 1989, five 3-year-old castrated male lambs (Pelib uey X Rambouillet), weighing about 39 kg, were used to determine month ly total fecal output. Feces were collected during 4 days, after a 5 d ay adjustment period. The in vitro organic matter digestibility (IVOMD ) was determined using esophageal extrusa samples collected from six e sophageally fistulated male lambs. Differences (P < 0.05) were found i n OM intake (OMI) among months (annual mean, 818.6 g day). In general, lambs consumed more OM during May, June and July. Digestible energy ( DE) intake was different (P < 0.05) among months. Annual mean was 1436 kcal DE per day. Lambs consumed more DE during May, and least during February. Crude protein intake was highest (P < 0.05) during July (189 .7 g day) and lowest in January (90.1 g day). Neutral detergent fiber intake (NDFI) was also dissimilar (P < 0.05) among sampling periods, t he highest NDFI being in July (974.3 g per day) and the lowest in the winter months. Acid detergent fiber intake of lambs followed a similar pattern to that of NDFI. Macro minerals consumed by lambs (K, Ca, Mg and Na) were in general higher (P < 0.05) during the summer months com pared with other months. Trace minerals (especially Cu and Fe, Zn and Mn) consumed by lambs also varied seasonally. In general, the results of this study indicate that only during the summer months do lambs con sume nutrients that meet or exceed their requirements.