|Lima, Gf Da - UNIVERSITY OF FLORIDA|
|Sollenberger, L - UNIVERSITY OF FLORIDA|
|Kunkle, W - UNIVERSITY OF FLORIDA|
|Moore, J - UNIVERSITY OF FLORIDA|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 17, 1999
Publication Date: February 17, 1999
Citation: Lima, G.C., Sollenberger, L.E., Kunkle, W.E., Moore, J.E., Hammond, A.C. 1999. Nitrogen fertilization and supplementation effects on performance of beef heifers grazing limpograss. Crop Science.39(6): 1853-1858. Interpretive Summary: Warm-season perennial grasses used as pasture or hay in Florida often do not meet the nutrient requirements of growing cattle. Floralta limpograss is an important perennial forage in the State because of its adaptation to poorly drained sites, relatively high digestibility, and better cool-season growth than other warm-season grasses. Low protein concentration of Floralta limpograss, however, limits gains of growing animals grazing pastures during summer. Objectives of this study were to determine the effect of increasing nitrogen fertilization rate of limpograss pastures on herbage protein concentration and forage digestibility, and to quantify the effects of pasture fertilization on weight gain of heifers (female cattle) grazing those pastures. In these experiments, we found that both nitrogen fertilization and heifer supplementation can be used to overcome protein deficiencies of heifers grazing limpograss.
Technical Abstract: This research evaluated management alternatives for increasing summer gains of beef replacement heifers (Bos spp.) on limpograss (Hemarthria altissima) pastures in Florida. During 1992 and 1993, a factorial arrangement of two pasture N fertilization rates (50 and 150 kg ha*1) and three diet supplements (NONE, corn [Zea mays L.] plus urea [CU], and CU plus rumen undegradable protein [CUUP]) were studied in two replications of a completely randomized design. Supplementation with CU increased heifer average daily gain (ADG) from 0.06 (NONE) to 0.41 kg on pastures fertilized with 50 kg ha*1 of N, but there was no ADG response to CU on pastures that received 150 kg ha*1 of N. When no supplement was fed, increasing pasture N fertilization from 50 to 150 kg ha*1 increased ADG from 0.06 to 0.36 kg and gain per hectare from 37 to 232 kg. Heifers receiving CUUP had greater gain per hectare (335 vs. 244 kg) and had (N rate of 50 kg ha*1) or tended to have (N rate of 150 kg ha*1) greater ADG than those receiving CU. Heifer blood urea N (BUN) concentration was low (4.2 mg dL*1) when no supplement was fed and pastures received 50 kg ha*1 of N, suggesting that low CP was limiting ADG. These data indicate that N deficiencies of cattle grazing limpograss can be overcome by increasing rate of pasture N fertilization or by providing N supplements.