Self‐Limiting Protein Supplements for Calves Grazing Bermudagrass Pastures

Low nutritive value of bermudagrass [Cynodon dactylon (L.) Pers.] and other warm‐season perennial grass pastures often limits acceptable animal performance of beef calves. Trials were conducted in 1986 and 1987 to determine the influence of source and level of self‐limiting protein supplements on performance of weaned, fall‐born 1/2 Simmental × 1/4 Brahman × 1/4 Hereford (Bos taunts) calves grazing bermudagrass pastures. In Trial 1, 36 steers and 36 heifers were allotted to two replicate groups of the following six treatments by weight (650 lb) and visual condition score: (i) bermudagrass pasture (PAS); (ii) PAS plus a commercially available condensed molasses block (CMB); (iii) PAS plus a condensed molasses block containing fishmeal (FMB); (iv) PAS plus a dry protein supplement (DRY); (v) DRY plus rumen‐stable methionine and lysine (DAA); and (vi) PAS plus a dry supplement containing fishmeal and monensin (FMR). The average daily gain (pounds per day) and conversion of supplement to extra gain for each treatment was PAS (1.04, 0:0), CMB (1.29,1.8:1), FMB (1.21, 2.7:1), DRY (1.52, 4.0:1), DAA (1.41, 5.9:1), and FMR (1.92,1.3:1). A comparison (P < 0.05) of treatments indicated the following average daily gain relationships: PAS = FMB = CMB < DRY < FMR, DAA = DRY, and FMB = CMB = DAA. In Trial 2, 30 steers and 40 heifers were allotted to two replicate groups by weight (620 lb) and visual condition score to the following five treatments: (i) PAS; (ii) CMB; (iii) PAS plus a dry supplement containing heat treated soybean meal, fishmeal, and monensin (SOY); (iv) PAS plus a dry supplement containing fishmeal (FIS); and (vi) FMR. The average daily gain for calves on PAS, CMB, SOY, FIS, and FMR was 0.84,1.10,1.54,1.37, and 1.49 lb/d, respectively, with conversion of supplement to extra gain at 0:0, 1.9:1, 1.5:1, 3.0:1, and 1.3:1, respectively. Treatment comparisons (P < 0.05) revealed that calf daily gains for PAS < CMB < FIS = FMR = SOY. There was a relatively efficient conversion of supplement to extra gain in both trials which suggests that low levels of supplemental protein increased bermudagrass use via intake, digestibility, or both.