Guilherme Ebling Rossi

Avaliação de espécies forrageiras de inverno na Depressão Central do Rio Grande do Sul

The experiment was carried out to evaluate the herbage production of cool season forage species and cultivars from Instituto Nacional de Investigacion Agropecuaria- INIA/Uruguay breeding program. The following species and cultivars were evaluated: Italian ryegrass (Lolium multiflorum Lam.): Cetus, Estanzuela 284 and Titan; Oats (Avena byzantina): RLE 115a and 1095a; White clover (Trifolium repens L.): Estanzuela Zapican; Red clover (Trifolium pratense L.): Estanzuela 116 and Birdsfoot trefoil (Lotus corniculatus L.) Sao Gabriel. Dry matter production, structural components percentage and production, canopy height, neutral detergent fiber, and crude protein percentages were determined. It was used a split-plot arrangement in a randomized block design, where the subplots were the evaluation dates, with four replications. Among the grasses, Italian ryegrass Titan presented the greatest herbage production of DM, with 7.2 t/ha and higher leaf proportion. The production of Birdsfoot trefoil and Red clover were similar and had greater DM production than White clover. The tested species and cultivars were adapted to the local conditions, even with rainfall deficit occurrence during the experimental period.

Sistemas de alimentação para a recria de ovinos a pasto: avaliação do desempenho animal e características da forragem

Um experimento foi conduzido na Fundacao Estadual de Pesquisa Agropecuaria (FEPAGRO), em Sao Gabriel, Rio Grande do Sul (RS), com objetivo de avaliar o desempenho de cordeiras em recria, as caracteristicas da pastagem, a composicao quimica e a cinetica de degradacao nas alternativas: pastagem cultivada de milheto (Pennisetum americanum (L.) Leeke) (PCM), pastagem natural (PN) e pastagem natural melhorada (PNM), que constituiram os tratamentos. O periodo de pastejo foi de 29 de janeiro a 14 de abril de 2005, sendo este caracterizado por uma forte estiagem. A PNM apresentou valores medios de massa de forragem superiores aos demais tratamentos, pela grande quantidade de material morto de azevem presente na forragem disponivel. A PCM apresentou maior proporcao de folhas em relacao a PN e a PNM. A carga animal media de 914kg de PV ha-1 da PCM foi superior a de 261kg de PV ha-1 e de 467kg de PV ha-1 da PN e da PNM, respectivamente. O ganho medio diario (GMD) no tratamento PCM (0,151kg dia-1) foi superior ao da PN (0,053kg dia-1) e da PNM (0,058kg dia-1), proporcionando maior peso vivo final (36kg de PV.animal-1) e escore corporal final (3,7 unidades) na PCM. Foram observados maiores valores de proteina bruta e menores de FDA e FDN na PCM em relacao a PN e a PNM. O volume final de gas, a taxa de degradacao e o tempo de colonizacao refletiram com precisao a composicao quimica e os ganhos de peso observados, sendo melhores para a PCM.

Structural and morphogenical characteristics of black oats and Italian ryegrass on pasture submitted to two grazing intensities

Morphogenical and structural characteristics of black oats (Avena strigosa Schreb.) and Italian ryegrass (Lolium multiflorum Lam.) on pastures managed under two grazing intensities were quantified by using marked tiller technique. The expected intensities of disappearance of forage mass initial value were 35% (low) and 65% (high). Experimental animals were sheep and interval among grazing was determined through 300 degree-day thermal sum. The experimental design was completely randomized with two grazing intensities and two replicates. Leaf blades of oats and ryegrass were removed at an average proportion of 57.5% of their initial length for both grazing intensities. Among the morphogenical characteristics of oats, only elongation rate of defoliate leaf differed between grazing intensities, with values of 0.059 and 0.081 cm/degree-day for low and high intensities, respectively. Grazing intensities did not alter structural characteristics of oats mixed with ryegrass and red clover. High grazing intensity enables maintenance of a higher number of ryegrass expanding leaves (1.7 leaves/tiller), thus it is suggested for management of pastures with oats mixed with Italian ryegrass and red-clover on intermittent grazing.

Valor nutritivo de gramíneas nativas do Rio Grande do Sul/Brasil, classificadas segundo uma tipologia funcional, sob queima e pastejo

Aiming to determinate the nutritive value and functional types classification consistency, crude protein and in vitro digestibility analysis were performed in leaf blades of the most frequent native grasses, in central RS. Species were evaluated under fire and grazing regimes: unburned and grazing excluded area (UE), burned and grazing excluded area (BE), unburned and grazed area (UG), burned and grazed area (BG) between 2007/September and 2008/May at Universidade Federal de Santa Maria experimental area. Crude protein ranged from 4.5 to 10.7% and digestibility showed greater variation, from 37 to 69%. Grazing affected positively crude protein in all species (7.9% in grazed area and 5.6% inexcluded area). Fire use promoted increase in grasses average digestibility (50.5% in burned area and 46.6% in unburned area). Crude protein and digestibility confirmed functional typology based in leaf traits, dry matter content and specific leaf area, based on which species are classified. Disturbances, grazing and fire, affect leaf blade nutritive value of several native grasses. Grazing increase mainly crude protein and fire increase digestibility.

Desempenho animal e produtividade de pastagens tropicais no noroeste do Rio Grande do Sul

Productivity of dwarf elephantgrass (Pennisetum purpureum Schum. cv. Mott) and tifton 85 (Cynodon dactylon x Cynodon nlemfuensis) pastures was evaluated under continuous grazing, in the Northwest area of Rio Grande do Sul. Twelve multiparous Holstein cows, at 100 days of lactation were evaluated and the put-and-take technique was used to regulate the stocking rate to maintain 4% of leaf lamina on offer. In the first year, dwarf elephantgrass and tifton 85 were different in leaf accumulation rates (31.2 vs 22.6kg/ha/day) and animal production (17.4 vs 20kg of milk/cow/day). In the second year, tifton 85 had higher leaf accumulation rates (38.8 vs 21.9kg/ha/day), stocking rate (2,157 vs 1,084kg of live weight/ha), and production per area (70 vs 41.3kg of milk/ha/day) than dwarf elephantgrass. Comparing the second to the first years, tifton 85 maintained 88% of stocking rate and 80% of production per area, while dwarf elephantgrass only 46% and 56%, respectively. Average individual production of 17kg of milk/cow/day indicates an unexplored potential of tropical grasses in dairy production systems, especially in the South of Brazil.