Effect of concentrate supplement to ewes on nutritive value of ingested Caatinga native forage nutritive value as affected by season.

The objective of this study was to identify by microhistological technique the reference chemical components for use as indicators of the nutritive value of Caatinga plants forage grazed by sheep throughout the year. A flock of twenty mixed-race meat ewes, multiparous, in production, with an average 34.84 ± 1.75 kg live weight and 36 months of age was assigned to supplement treatment of 0, 200, 350, and 500 g concentrate/head/day for 3 years. The experiment was designed as a randomized complete design with repeated measures over time. Supplementation with concentrate did not influence chemical composition of selected forage. In contrast, season heavily influenced diet chemical composition. Canopy stratum, season, and plant botanical family of selected species affected forage chemical composition selected by ewes. The ewes selected forage with greater nutritive value during the rainy season. Based on principal component analysis of the nutritive value of the primary forage species selected, ewes preferentially grazed plants contained greater neutral detergent fiber, acid detergent fiber, crude protein (CP), C fraction of nitrogenous compounds, and carbohydrate fractions A + B1 and C compared to the average native Caatinga herbage. Rangeland botanical composition and ewe diet varied during the year, affecting forage nutrients on offer, with the best diet selected during the rainy season because of the presence of dicotyledonous herbaceous species rich in CP as well as soluble carbohydrates and nitrogenous compounds. Concentrate supplement strategies for ewes on rangelands, such as Caatinga, should be determined by herbaceous species nutritive value during the rainy season and deep-rooted perennial dicotyledons during the dry season. These include the need to monitor ewe selection of forage species and their nutritive value, which is effectively accomplished with fecal microhistological techniques.

Desempenho animal e produtividade de pastagens tropicais no noroeste do Rio Grande do Sul / Animal performance and productivity of tropical pasture in Northwest of Rio Grande do Sul

Avaliou-se a produtividade do capim-elefante anão e do tifton 85 sob pastejo contínuo no noroeste do Rio Grande do Sul, utilizando-se 12 vacas da raça Holandesa, multíparas e com cerca de 100 dias de lactação. Foi aplicada a técnica dos animais reguladores para ajustes da carga animal de forma a manter a oferta de lâminas foliares de 4 por cento. No primeiro ano experimental, o capim-elefante anão e o tifton 85 apresentaram diferenças significativas quanto às taxas médias de acúmulo de lâminas foliares (31,2 vs 22,6kg/ha/dia) e produção animal (17,4 vs 20kg de leite/vaca/dia). No segundo, o tifton 85 foi superior ao capim-elefante anão quanto à taxa de acúmulo de matéria seca de lâminas foliares (38,8 vs 21,9kg/ha/dia), capacidade de suporte (2157 vs 1084kg de peso vivo/ha) e produções por área (70 vs 41,3kg de leite/ha/dia). No segundo ano, em relação ao primeiro, o tifton 85 manteve 88 por cento da capacidade de suporte e 80 por cento da produção por área, enquanto o capim-elefante anão apenas 46 por cento e 56 por cento. A produção média de 17kg de leite/vaca/dia indica um potencial pouco explorado das gramíneas tropicais em sistemas de produção de leite, especialmente na região Sul do Brasil.

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 percent 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 percent of stocking rate and 80 percent of production per area, while dwarf elephantgrass only 46 percent and 56 percent, 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.