Warm-season grasses require N fertilization to achieve their full production potential; however, increased costs have limited the use of N by beef cattle (Bos spp.) producers. Th e objective of this study was to test the eff ects of two grazing frequencies (2 and 4 wk) on production, nutritive value, and persistence of 'Argentine' (tetraploid), 'Pensacola', 'Tift on 9', and 'UF Riata' (diploids) bahiagrass (Paspalum notatum Flügge) cultivars fertilized with 60 kg N ha -1 yr -1 . Th e study was conducted in Ona, FL, from January 2010 to December 2011. Treatments were eight factorial combinations of two grazing frequencies (2 and 4 wk) and four bahiagrass cultivars. Th e four cultivars were grazed by beef cows (505±30 kg) for approximately 8 h to a 7.5-cm stubble height at 2-or 4-wk intervals. Diploid cultivars had greater herbage accumulation (HA) in the spring; however, Argentine had greater annual HA in 2010 and 2011. Plots grazed at 4 wk had approximately 50% greater HA than 2-wk grazing frequency. Argentine and Pensacola had greater root and rhizome mass than Tift on 9 and UF Riata when grazed every 2 wk, while Argentine had greater cover than any of the diploids when grazed at the 2-wk frequency. Results show that Argentine is a productive and persistent bahiagrass for beef cattle producers using limited N fertilization and frequent grazing in Florida. Decreasing grazing frequency is an eff ective management practice to increase bahiagrass HA and persistence, particular the upright-growing Tift on 9 and UF Riata.

Brachiaria 'Mulato II' is a hybrid brachiaria grass with superior nutritive value when compared with other warmseason grasses. The performance of 2 new brachiaria grass hybrids was compared with that of Mulato II in terms of herbage accumulation, nutritive value and ground cover in a series of experiments. In Experiment 1, Mulato II and lines BR02/1752 (now cv. Cayman) and BR02/1794 were harvested at 3-and 6-wk regrowth intervals in South Florida. Mulato II had greater herbage accumulation and ground cover than Cayman and BR02/1794, while Mulato II and Cayman had greater in vitro digestible organic matter (IVDOM) concentration than BR02/1794. Regrowth interval did not affect herbage accumulation and ground cover but herbage harvested at 3-wk intervals had greater nutritive value than 6-wk regrowth. In Experiment 2, Mulato II had similar IVDOM and CP concentrations to but greater herbage accumulation, ground cover and plant density than Cayman in North-Central Florida. In Experiment 3, Mulato II and Cayman plots were grazed at 2-, 4-or 6-wk intervals, and herbage accumulation and nutritive value were similar for both cultivars. Herbage nutritive value decreased and ground cover increased linearly as regrowth interval increased from 2 to 6 wk, and Mulato II had greater ground cover than Cayman. The new hybrids displayed no production or nutritive value advantages over Mulato II; regrowth intervals of less than 3 wk should be avoided to maintain Brachiaria hybrid stands in this subtropical environment. ResumenEl híbrido de braquiaria Mulato II es un cultivar (cv.) con valor nutritivo superior al de otras gramíneas de clima cáli-do. En la Florida se compararon, en 3 experimentos, 2 nuevos híbridos de braquiaria: las líneas BR02/1752 (ahora: cv. Cayman) y BR02/1794, con cv. Mulato II, en términos de producción de forraje, valor nutritivo y cobertura del suelo. En el primer ensayo, conducido en el sur de la Florida y con intervalos de corte de 3 y 6 semanas, el cv. Mulato II presentó mayor producción de forraje y cobertura que el cv. Cayman y la línea BR02/1794, mientras que los cvs. Mulato II y Cayman presentaron mayor digestibilidad in vitro de la materia orgánica (DIVMO) que la línea BR02/1794. El intervalo de corte no afectó la producción de forraje y la cobertura pero en los cortes cada 3 semanas el valor nutritivo fue mayor que en los cortes cada 6 semanas. En el segundo ensayo, conducido en el centro-norte de la Florida, Mulato II presentó valores de IVDMO y concentración de proteína cruda similares a cv. Cayman, pero mayor producción de forraje, cobertura y densidad de plantas. En un tercer ensayo, también en el centro-norte de la Florida, los cvs. Mulato II y Cayman fueron sometidos a pastoreo cada 2, 4 y 6 semanas. Aquí, la producción de forraje y el valor nutritivo de ambos cultivares fueron similares. El valor nutritivo disminuyó mientras que la cobertura aumentó en forma lineal a medida que el intervalo de pastoreo aumentó de 2 a 6 semanas; el cv. Mulato II tuvo mayor cobertura que el cv. Cayman. ...

‘Jiggs’ bermudagrass [Cynodon dactylon (L.) Pers.] is a productive forage in the southeastern United States; however, there is limited information on grazing management of this bermudagrass ecotype. The objective of this study was to test the effects of different stocking rates on animal performance and herbage characteristics of Jiggs pastures. The experiment was conducted in Ona, FL, from May to August 2011 and 2012. Treatments were three stocking rates, 3.0 (low), 7.5 (medium), and 12.0 animal units (AU = 450 kg liveweight [LW]) ha−1 (high). The animals received 10 g kg−1 LW concentrate supplement daily during the experimental period. Heifer weight was recorded every 28 d and herbage parameters were measured every 14 d. There was a linear decrease (P < 0.01) in herbage mass (HM, from 3.8 to 2.4 Mg ha−1), light interception (from 94 to 71%), forage height (from 17 to 9 cm), and herbage allowance (HA, from 2.3 to 0.4 kg dry matter kg−1 LW) with increasing stocking rate. There was no effect (P > 0.10) of stocking rate on herbage nutritive value. Jiggs ground cover decreased (P < 0.01) from 95 to 39% with increasing stocking rates. Heifer average daily gain decreased (P < 0.01, from 0.7 to 0.3 kg d−1) and gain per hectare (P = 0.01, from 692 to 1064 kg ha−1) increased as stocking rate increased. Despite greater gain per hectare with increasing stocking rate, continuously stocked Jiggs should not be grazed below 17‐cm stubble height during the growing season to maintain the stand.

The objective of this study was to evaluate the effects of monensin supplementation on animals receiving warm-season grass with limited supplementation. In Exp. 1, treatments were a factorial combination of 2 stocking rates (1.2 and 1.7 animal unit [AU] [500 kg BW]/ha) and supplementation with monensin (200 mg/d) or control (no monensin) distributed in a complete randomized design with 3 replicates. Thirty Angus × Brahman crossbred heifers (Bos taurus × Bos indicus) with initial BW of 343 ± 8 kg were randomly allocated into 12 bahiagrass (Paspalum notatum) pastures and supplemented with 0.4 kg DM of concentrate (14% CP and 78% TDN) daily for 86 d. Herbage mass (HM) and nutritive value evaluations were conducted every 14 d, and heifers were weighed every 28 d. There was no effect (P ≥ 0.97) of monensin on HM, herbage allowance (HA), and ADG; however, animals receiving monensin had greater (P = 0.03) plasma urea nitrogen (PUN) concentrations. The stocking rate treatments had similar HM in June (P = 0.20) and July (P = 0.18), but the higher stocking rate decreased (P < 0.01) HM and HA during August and September. Average daily gain was greater (P < 0.01) for the pastures with the lower stocking rate in August but not different in July and September (P ≥ 0.15). Gain per hectare tended to be greater on pastures with the higher stocking rate (P ≤ 0.06). In Exp. 2, treatments were 3 levels of monensin (125, 250, and 375 mg/animal per day) and control (no monensin) tested in a 4 × 4 Latin square with a 10-d adaptation period followed by 5 d of rumen fluid collection and total DMI evaluation. Blood samples were collected on d 4 and 5 of the collection period. Ground stargrass (Cynodon nlemfuensis) hay (11.0% CP and 52% in vitro digestible organic matter) was offered daily. The steers received the same supplementation regimen as in Exp. 1. Total DMI was not different among treatments (P = 0.64). There was a linear increase (P ≤ 0.01) in propionate and a tendency for decreased acetate (P ≤ 0.09) concentrations in the rumen with increasing levels of monensin; however, there was no effect (P ≥ 0.19) of monensin levels on ruminal pH and ruminal concentrations of butyrate and ammonia. In addition, there was no effect (P ≥ 0.73) of monensin levels on plasma concentrations of glucose, insulin, IGF-1, and PUN. In summary, monensin supplementation effects were not detected at either stocking rate and may not be effective in increasing performance of beef cattle grazing low-quality warm-season grasses with limited supplementation.

Despite scientific evidence suggesting that warm‐season grasses can respond favorably to K and P fertilization, the increasing costs of fertilizers limit the extent to which these nutrients are used in pastures and hayfields. Two field studies evaluated ‘Jiggs’ bermudagrass [Cynondon dactylon (L.) Pers.] and ‘Floralta’ limpograss (Hemarthria altissima Stapf. and Hubbard) herbage accumulation (HA), nutritive value, and persistence to reduced fertilization strategies during 2012 to 2014. Treatments were allocated in a split‐plot design with N (90 or 180 kg N ha−1, bermudagrass study) or harvest frequency (6 vs. 12 wk, limpograss study) as the main factors and P (0, 8.7, and 17.4 kg P ha−1) and K (0, 33, and 66 kg K ha−1) levels as subplots. Bermudagrass HA increased linearly (up to 377% in Year 3) as K level increased. Similarly, K fertilization increased limpograss HA from 8.4 to 11.6 Mg ha−1 in 2013 and from 5.8 to 15.7 Mg ha−1 in 2014 as K levels increased from 0 to 66 kg K ha−1; however, no effect was observed in 2012. Bermudagrass HA and ground cover decreased from 2012 to 2014 in all K treatments. Conversely, decreases in limpograss HA and ground cover over time were observed only in the control (no K) treatments. Bermudagrass and limpograss crude protein concentrations generally decreased with increased K level. No effects of N or P were observed. Continuous aboveground removal without proper K fertilization is detrimental to bermudagrass and limpograss production and persistence.