Carlos Augusto Brandão de Carvalho

Desempenho de ovinos e respostas de pastagens de tifton 85 (Cynodon spp.) sob lotação contínua

ABSTRACT: The use of pastures for feeding ruminants is increasing in recent years due to its low cost comparativelyto other sources of feed. In that sense, forage plants with good performance under grazing and presenting highflexibility of utilisation have raised a great deal of interest. In this context, pasture and animal performance wereevaluated on Cynodon spp. (cultivar Tifton 85) swards kept in four steady state conditions (50, 100, 150 and 200 mmsward surface heights - SSH) with sheep grazing under continuous stocking and variable stocking rate from august/1998 to april/1999. Treatments corresponded to the SSH and were allocated to experimental units according to acomplete randomised block design with four replications. Individual experimental units (400 2 each) were grazed,mat least, by two lambs to estimate animal responses, with three exclosure cages for herbage accumulationmeasurements. Experimental responses evaluated were: crude protein (CP), neutral detergent fiber, acid detergentfiber and lignin, and

Dry matter accumulation dynamics in grazed Tifton 85 bermudagrass swards

Herbage dry matter accumulation from forage plants results from the balance between growth and senescence. Agronomic practices may influence both processes in different ways and, therefore, alter the quantitative and qualitative patterns of dry matter production. This study aimed at evaluating the process of dry matter accumulation through measurements of growth and senescence. Experimental treatments corresponded to four sward state conditions (5, 10, 15 and 20 cm of sward surface height - SSH) generated by sheep grazing under continuous stocking and variable stocking rate. The experimental design was a complete randomised block, with four treatments and four replicates. Pasture responses evaluated were: stem elongation, leaf lamina elongation, senescence, phyllochron and number of leaves per tiller. The results showed a seasonal pattern of herbage production with the highest growth and senescence rates observed at the highest SSH studied (15 and 20 cm). Phyllochron varied according to time of the year and SSH, revealing an intimate relationship with air temperature variation, soil water availability and sward leaf area index. SSH of 15 and 20 cm resulted in the highest dry matter production. The same principles and relationships originally described for herbage accumulation in temperate grass pasture species are valid for tropical areas within the framework of the physiological and environmental constraints inherent to each condition.

Índice de área foliar, interceptação luminosa e acúmulo de forragem em pastagens de Cynodon spp. sob diferentes intensidades de pastejo

Leaf area index (LAI), light interception and herbage accumulation were evaluated for three Cynodon spp. cultivars (Tifton-85, Florakirk and Coastcross) submitted to four grazing intensities (5, 10, 15 and 20 cm) established by sheep under a continuous stocking management. A complete randomised block design was used with four replications, with treatements in a split-plot arrangement. Grass cultivars were allocated to plots and grazing intensities to sub-plots. The largest values of LAI were observed for Tifton-85. Rates of dry matter accumulation were similar for all treatments. Tifton-85 presented a narrower optimal range for pasture conditions (5 to 15 cm) as compared to Florakirk (5-20 cm) and Coastcross (5-20+ cm). Different grass cultivars presented different grazing management requirements in situations where the efficient use of light and high levels of herbage utilisation were targeted.

Índice de área foliar, coeficiente de extinção luminosa e acúmulo de forragem em pastagens de Cynodon spp. sob lotação contínua

Leaf area index, light extinction coefficient and herbage accumulation were evaluated in three Cynodon spp. cultivars (Tifton85, Florakirk and Coastcross) submitted to four grazing intensities (5, 10, 15 and 20cm) imposed by sheep under a continuous stocking management. The experimental design was a complete randomized blocks with four replications, with treatments in a split plot arrangement. Grass cultivars were allocated to plots and grazing intensities to subplots. The largest values of LAI were observed for Tifton85. Light extinction in the sward was a function of grass cultivar, time of the year and phenological state of pasture plants. Florakirk presented the highest values of light extinction coefficient (k), but k was higher for lower grazing intensities. No differences were observed in herbage accumulation rates among the grass plants studied.

Dinâmica do perfilhamento em capim-elefante sob influência da altura do resíduo pós-pastejo

The objective of this work was to evaluate the effects of two stubble heights (50 and 100 cm) on tiller dynamics, dry mass for tiller and dry mass herbage accumulation of basal and aerial tillers in elephantgrass pastures managed under grazing. A complete randomized block design with split plot arrangement and four replications were used. The stubble heights did not influence the population density, tiller mortality and birth percentage, dry mass per tiller and herbage accumulation of basal and aerial tillers. Basal and aerial tillers showed increase of 47% and reduction of 16% on population density between spring and summer, respectively. Tillers with leaves were 92% of aerial tillers and 52% of basal tillers. Tiller birth percentage was the highest determinant of population density variations. The dry mass herbage accumulation was larger for basal tillers during spring, and the aerial tillers increased it during summer.

Production and quality of milk from Mantiqueira dairy cows feeding on Mombasa grass pasture and receiving different sources of roughage supplementation

Production and quality of milk from dairy cows grazing exclusively on Mombasa grass pasture, during the spring-summer period and fed roughage supplementations, during the autumn-winter, were evaluated in two consecutive years. The pasture of 11.4 ha was divided into 57 paddocks of 2,000 m2 each, including three replications with 19 paddocks each. The pasture was managed with two occupation days and 36 resting days. During the spring-summer period, cows received only grass pasture. In the autumn-winter period, they had access to Mombasa grass pasture and received roughage supplementations (black oat pasture; sorghum silage or sugarcane + urea) and pasture every 28 days, alternately. The animals had access to mineral mix and water and received 500 g of concentrated in each of the two milking times. The experimental design used was for response to continuous flow in rotational trial, similar to the Latin square model. In the spring-summer period, the average milk production was 12.2±2.2 and 14.0±3.8 kg/cow per day; for the autumn-winter period, the milk production was 13.5±2.9 and 12.1±2.5 kg/cow per day in the black oat pasture; 11.8±2.5 and 10.9±2.3 kg/cow per day in the sorghum silage and 11.3±1.8 and 8.4±1.5 kg/cow per day in the sugarcane + urea, for 1st and 2nd years evaluated, respectively. The black oat was the roughage supplementation that yielded the highest average daily milk production. There were no differences in the milk chemical composition between roughage supplementations.