PROTEIN SUPPLEMENTATION OF STEERS GRAZING LIMPOGRASS PASTURE

A decrease in average daily gain (ADG) is observed usually during mid-summer through early fall with growing cattle (Bos sp.) grazing 'Floralta' limpograss [LG; Hemarthria altissima (Poir.) Stapf et C.E. Hubb.] pasture. Reports of low crude protein (CP) concentration in LG have led to speculation that a limitation of dietary CP contributes to low ADG. In 1987 and 1988, 84-d grazing studies were conducted on Pomona sands (sandy, siliceous, hyperthermic Ultic Haplaquods) to determine the effect of N supplementation [urea plus a corn (Zea mays L.) meal carrier] on animal performance of steers grazing rotationally on LG pasture during the summer-slump period. Nonsupplemented steers (NP) gained 0.64 lb/d over the 2 yr. Supplementing steers daily with rations containing 1.29 lb corn and 0.06 lb urea (21% CP, LO) or 1.29 lb corn and 0.256 lb urea (50% CP, HI) resulted in an 80 to 100% increase in seasonal ADG over that on NP (LO, 1.17 lb/d; HI, 1.30 lb/d). Steer ADG was approximately 80% greater for an LG-aeschynomene (Aeschynomene americana L.) mixture (LA; 1.17 lb/d) than for NP, but was not different from that for the HI or LO treatments. Gain per acre was not different for LO and HI, averaging 257 lb. Gain/acre for NP averaged 150 lb and was lower than that for the supplementation treatments, but it was not different from (hat for LA (151). Steer plasma urea N concentrations were greater for HI (11.4 mg/100 ml) than for LO (8.2) or NP (6.0). Feeding a corn-urea supplement to steers grazing LG pasture may be an effective and economical approach to improving animal performance during midsummer through early fall. It appears to be more reliable than use of annual legume-LG associations because of frequent drought-induced legume stand failures.