INITIAL HEIGHT AND DEFERMENT PERIOD ON SIGNALGRASS PASTURES

This study aimed to evaluate the initial heights (10, 20, and 30 cm) and deferment periods (171, 141, and 109 days in 2010; and 131, 100, and 71 days in 2011) of Urochloa decumbens cv. Basilisk (signal grass). The factors were arranged in split plot, in a randomized complete block design with three replications. Pastures deferred for a short period had lower masses of forage (5,977 and 6,904 kg/ha of DM in 2010 and 2011, respectively). In 2010, pastures deferred for a short period had lower mass of live stem (942 kg/ha of DM), dead leaf blade (785 kg/ha of DM), and dead stem (1282 kg/ha of DM), higher number of vegetative tillers (797 tillers/m²), fewer reproductive tillers (2 tillers/m²), less falling index (1.4), higher mass of live leaf blade (655 kg/ha of DM). The higher pastures had fewer vegetative tillers (495 and 431 tillers/m² in 2010 and 2011, respectively), larger masses of forage (5,285 and 5,942 kg/ha of DM in 2010 and 2011, respectively), dead leaf blade (968 kg kg/ha of DM in 2010) and dead stem (1,902 kg/ha of DM in 2010). Based on the results obtained in the two years, for use in July, the signal grass can be deferred for 71-109 days with an initial height of 20 to 30 cm. The initial height of 10 cm is recommended when a deferral period above 130 days is adopted.Keywords: Brachiaria decumbens; forage mass; sward height; tiller

Longevidade de larvas infectantes de Haemonchus sp. em duas alturas de pasto de Brachiaria brizantha cv. Marandu

O objetivo deste trabalho foi quantificar a recuperação de larvas infectantes de Haemonchus sp. em capim Marandu (Brachiaria brizantha), no período da seca (inverno) e das chuvas (verão) ao longo do tempo; bem como verificar se a altura do pasto influenciou neste tempo de sobrevivência. O experimento foi conduzido em Uberlândia, durante os meses de agosto a novembro de 2014 (seca) e janeiro a março de 2015 (chuvas). Foram considerados dois tratamentos (alturas de pasto 10 e 35cm), com coleta de amostras nos dias 0, 7, 14, 28, 42, 56 e 70 dias. Houve contaminação experimental de parcelas com fezes de caprinos com média de 1600 ovos de estrongilídeos por grama (OPG). Foi realizada amostragem por cortes dos estratos inferior e superior do capim. Houve maior número de larvas recuperadas no estrato inferior no inverno (p<0,05). Não houve diferença no número de larvas recuperadas dos diferentes estratos no verão, nem entre as diferentes alturas de pasto (p>0,05). Foram encontradas larvas até o 42o dia no período chuvoso e até o fim do trabalho durante a seca, com maior quantidade de larvas (p<0,05) no 7º e 14º dia pós-contaminação. Pode se inferir a necessidade de estudos para maior conhecimento da influência das variáveis microclimáticas do pasto nas larvas infectantes de nematódeos

Forage mass and structure of piatã grass deferred at different heights and variable periods

The objective of this study was to determine the deferment period and the most adequate initial sward height of Brachiaria brizantha cv. Piatã for deferment in the region of Viçosa, Minas Gerais. For so, the following characteristics were evaluated: masses and bulk density of forage and its morphological components, light interception by the sward, leaf area index, leaf angle, sward and extended tiller height and falling index of the deferred piatã grass. The three deferment periods assessed (65, 85 and 105 days) were randomized to the plots and the three sward heights (20, 30 and 40 cm), randomized in the subplots. The experimental design was of completely randomized blocks, with three replicates, in a subdivided plots arrangement. Masses of forage, green stem and dead tissue were higher in the piatã grass managed with deferment period of 105 days. The mass of green leaf blade was higher in the piatã grass deferred with 20 cm height associated to the deferment period of 85 days, which had, as consequence, greater bulk density of green leaf blade. The interception of light by the sward was greater in the piatã grass kept longer in deferment associated with the higher leaf area index, regardless of its initial height. The heights of the sward and extended tillers were greater in the piatã grass under periods of 85 and 105 days of deferment; however, the falling index was not affected by the factors studied. In the region of Viçosa, Minas Gerais, B. brizantha cv. Piatã fertilized with 75 kg/ha nitrogen and deferred with initial height of 20 cm and for a period of 85 days, from mid April, has adequate productivity and structure for animal production

Marandu palisade grass management strategies at the beginning of the deferment period and effects on tillering

Pasture mowing at the beginning of deferment stimulates tillering and can be used in different ways. The aim of this study was to understand how the mowing of Urochloa brizantha cv. Marandu Syn. Brachiaria brizantha cv. Marandu (marandu palisade grass) prior to the deferment period modifies tillering activity and the characteristics of young, mature, and old tillers. Three mowing strategies were evaluated: canopies kept at a height of 15 cm for five months before deferment (15/15 cm); canopies kept at 30 cm (30/15 cm) or 45 cm (45/15 cm) for five months before deferment and posteriorly cut to 15 cm at the start of the deferment period. The structural characteristics of young, mature, and old tillers of marandu palisade grass were compared only at the end of the deferment period. The tiller appearance rate was greater before (16.0%) than during (6.4%) the deferment period, but a contrasting response pattern was observed for the tiller mortality rate. The defoliation strategies that resulted in greater numbers of tillers in the canopies were 30/15 cm (2,098 tillers m-²) and 45/15 cm (2,160 tillers m-2). The defoliation strategy that generated the greatest percentage of young tillers in the canopy was 45/15 cm (26.1%), while the percentage of old tillers was greater in the canopies submitted to the 15/15 cm (64.1%) and 30/15 cm (61.5%) strategies. Weight and percentage of live stems of mature and old tillers were greater in relation to young tillers. The percentage of live leaves was grater in young tillers (52.6%), intermediate in mature tillers (41.4%), and lower in old tillers (21.3%). Regarding the percentage of dead leaves, the opposite trend was observed, where the percentage was greater in the old than in young tillers. Leaf area was greater in mature tillers (55.3 cm²) than in old tillers (29.2 cm²). Mowing of the marandu palisade grass to 15 cm at the beginning of the deferment period increases the number of young tillers, which have a more favorable morphological composition than mature and old tillers

Number and morphology of tiller age groups during summer in Marandu palisadegrass pastures previously used under deferred grazing

The relative contribution of young, mature and old tillers in the canopy influences the production and structure of the pasture. The objective with this work was to evaluate the balance between tiller appearance and tiller death (BAL) during spring and early summer, the morphology and percentages of young, mature and old tillers in Brachiaria brizantha cv. Marandu (marandu palisadegrass) with three conditions in late winter: short (24.1 cm), tall (49.0 cm) and tall (50.0 cm)/mown (8 cm). Tall and tall/mown pastures presented higher BAL in September and October, respectively. In January, BAL was higher in short and tall/mown pastures than in tall pasture. The tiller number was higher in short pasture, intermediate in tall/mown pasture and lower in tall pasture. The percentage of old tillers was higher in short and tall pastures compared to tall/mown pasture. The percentage of live leaf lamina reduced, while the percentage of dead leaf lamina increased with tiller age. Mowing of the tall marandu palisadegrass pasture in late winter increases the renewal of tillers in the spring and decreases the percentage of old tillers in the summer. The old tillers present worse morphology than young tillers

Mowing and lowering the marandu palisadegrass sward height at late winter improve the sward structure

The structure of the sward is important because it influences the responses of plants and animals in grazing conditions. The objective with this work was to evaluate the structural characteristics of the Marandu palisade grass pasture (Brachiaria brizantha syn. Urochloa brizantha) during spring and summer, depending on the condition of the sward at the end of winter. Four grazing conditions at the end of winter were evaluated: short (24.1 cm), short (25.2 cm)/mown (8 cm), tall (49.0 cm) and tall (50.0 cm)/mown (8 cm). The foliar area index was lower in the tall pasture than in the tall/mown pasture. The mass and the volumetric density of dead stem were higher in the tall pasture, intermediate in the short pasture, and lower in mowed pastures. At the beginning of the grazing period, the live stem mass was higher in the tall pasture. At the beginning and middle of the grazing period, the volumetric density of dead leaf lamina was lower in mowed pastures. At the beginning of the pasture period, the short pasture had a higher tiller number (TN). In the middle of the grazing period, the short and short/mown pastures had higher TN. At the end of the pasture period, the lowest TN value occurred in the tall pasture. The tall pasture at the end of winter presents an unfavorable structure to the animal in grazing, while the mowing and reduction in the height of the marandu palisade grass improves the structure of the sward in spring and summer