PERFORMANCE OF YEARLING AND WEANLING CATTLE GRAZING BERMUDAGRASS PASTURES WITH A SELF-LIMITING PROTEIN-SUPPLEMENT

The stocker cattle grazing enterprise in the southeastern USA has been hindered by unacceptable performance of animals grazing bermudagrasse s [Cynadon dactylon (L.) Pers.] and other warm-season perennial grasse s, particularly during the latter stages of the grazing season. The ob jective of this study was to determine the effect of a self-limiting p rotein supplement on performance of yearling and weanling cattle (Bos taurus x B. indicus) grazing bermudagrass pastures. The 2-yr study was conducted in 1990 and 1991 and included 180 yearling cattle and 80 we anling calves that were randomly allocated to replicate groups of the following two treatments: (i) bermudagrass pasture alone (BGPAS); and (ii) bermudagrass pasture supplemented with a 28% crude protein conden sed molasses block (PMB). Stocking rates of three yearlings or five we anlings per acre were maintained throughout the study. Durations of th e grazing seasons for 1990 and 1991 were 112 and 152 d, respectively. Yearlings fed PMB had average daily gains, total gains, and final weig hts that were 0.31 lb/d, 39 lb, and 41 lb heavier (P < 0.03), respecti vely, than those grazing BGPAS alone. Daily gains and final weights of PMB-supplemented weanlings were 0.23 lb/d and 40 lb greater (P < 0.09 ), respectively, than non-supplemented weaned calves. Average daily co nsumption (lb/d) and conversion of supplement intake to additional gai n (lb:lb) were 0.85 and 2.74:1 for yearlings, and 0.77 and 3.35:1 for weanlings. Individual sales value of supplemented yearlings and weanli ngs tended to be higher (P < 0.12) than that of unsupplemented cattle. Both age groups responded beneficially to the PMB supplement during t he early portion of the grazing season, but supplementation failed to offset the reduced daily gains that occurred during the latter part of the grazing season.