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 experiment was carried out on Cynodon spp cv. Tifton 85 pastures grazed by sheep under rotational stocking, with the objective of evaluating the structural characteristics as well as the forage mass of the pastures subjected to three grazing intensities in successive cycles. Treatments were composed of three residual leaf area indices (rLAI; 2.4; 1.6 and 0.8), allocated in completely randomized blocks with seven replications, totaling 21 experimental units. Tiller population density, pasture height, leaf area index, forage morphological composition and pasture forage mass were evaluated. The rLAI modified the tiller population density, which increased linearly with decrease in the rLAI of the pastures. Dry masses of leaf blade, stem and dead material were inferior when the rLAI imposed were lower, which resulted in differentiated forage production among the treatments. Tifton 85 pastures grazed by sheep in rotational stocking under tropical conditions with different rLAI show a modified sward structure over successive grazing cycles, mainly by alteration in the height and LAI of the plants at pre-grazing and by light interception post-grazing, which change the tiller population density. The residual leaf area index of 1.6 is the most suitable for pasture management for being equivalent to the heights of entrance and exit of animals on and from paddocks of 33 and 19 cm, respectively, which avoid great accumulation of dead material and excessive stem elongation, in addition to ensuring tillering in the sward.

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.

This study was carried out to analyze the tillering profile of Guinea grass (Panicum maximum cv. Tanzania) pastures subjected to two grazing frequencies (time necessary to intercept 90 and 95% of the incoming light) and two post-grazing heights (30 and 50 cm) in the period from November 2005 to October 2006. The experimental design was of completely randomized blocks with three replications, in a 2 × 2 factorial arrangement. At the end of the spring, pastures managed with 90% light interception showed greater tiller appearance rates in relation to pastures managed with 95%, regardless of post-grazing height. In the summer and fall, pastures managed with post-grazing height of 30 cm showed higher tiller appearance rates in comparison with pastures managed at 50 cm, regardless of grazing frequency. Concerning the tiller mortality rates, in the summer, higher values were found for pastures managed at 90/50 and 95/30 (interception/ height), intermediate values at 90/30 and lower values in those managed at 95/50. Pastures managed at 90/30, 95/30 and 95/50 in the fall presented greater tiller mortality rates than those managed at 90/50. These differences do not occur in the winter/beginning of spring. The stability index remained above 1 all through the experimental period. All management strategies evaluated are adequate for Guinea grass.

The use of nitrogen fertilization in tropical grasslands is a strategy that may reduce the pressure of livestock production on biome areas with humid forests. The objective of this study was to assess the use of different doses of nitrogen in Guinea grass (Megathyrsus maximus (Jacq.) con. Mombasa) cultivated in the humid tropics. Doses of 0, 10, 20, 30, 40, and 50 kg of N ha−1 application−1 were applied during two consecutive years in experimental plots. The experimental area is located in the northeast of Pará, Brazil, with a predominantly tropical climate according to the Köppen classification. The morphogenic, production, and qualitative characteristics of the forage were evaluated. The morphogenic variables, rate of leaf appearance and rate of leaf elongation, in addition to daily accumulation of forage and crude protein content, increased with increasing doses of nitrogen. The morphological structure of the pasture was not modified. The number of cuts increased, whereas the number of days of recovery decreased, in the rainy season with increasing doses of nitrogen. The use of nitrogen fertilization does not alter the structure of the pasture; however, it improves the morphogenic, production, and chemical characteristics of Guinea grass.

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RESUMOForam avaliados os efeitos de duas doses de nitrogênio aplicadas em cobertura sobre as características morfogênicas e estruturais dos híbridos de sorgo (Sorghum bicolor (L.) Moench) BRS 801 e 0734006 cultivados em vasos ao ar livre. O delineamento experimental foi inteiramente casualizado com os quatro tratamentos arranjados em esquema fatorial 2x2 (dois híbridos de sorgo e duas doses de nitrogênio, 50 kg ha -1 e 100 kg ha -1 ) com oito repetições. Constatou-se efeito significativo da interação híbrido x adubação sobre a taxa de aparecimento de folhas, sendo que o híbrido BRS 801 se mostrou mais responsivo ao aumento da dose de nitrogênio. O filocrono, o número total de folhas e a taxa de alongamento foliar, foram influenciados tanto pela dose de nitrogênio quanto pelos híbridos utilizados. A taxa de senescência foliar não foi influenciada pelos fatores adubação e híbridos. As variações das características morfogênicas e estruturais entre os híbridos e/ou doses de adubação, indicam que, provavelmente, os híbridos respondem de maneira diferenciada às adubações de cobertura.Palavras-chave: filocrono, forrageira anual, nitrogênio, taxa de aparecimento de folhas, taxa de alongamento de folhas Morphogenetic and structural characteristics of sorghum hybrids submitted to the nitrogen fertilization ABSTRACTThe effect of two topdressing nitrogen doses was evaluated on the morphogenetic and structural characteristics of sorghum hybrids (Sorghum bicolor (L.) Moench) BRS 801 and 0734006, cultivated in vases in open-air conditions. A completely randomized design was used with four treatments arranged in factorial outline 2x2 (two sorghum hybrids and two nitrogen doses, 50 and 100 kg ha -1 ), with eight replications per treatment. There was a significant effect of interaction hybrid x fertilization on the leaf appearance rate, the hybrid BRS 801 being more responsive to the increased nitrogen dose. The phyllochron, the total number of leaves and leaf elongation rate, were influenced both by nitrogen doses and by hybrids. The leaf senescence rate was not influenced by factors fertilization and hybrids. These variations in morphogenetic and structural characteristics between the hybrids and/or nitrogen doses, probably indicate that hybrids respond in a different way to topdressing.