Two experiments were conducted to assess the effect of pre‐grazing heights and proportions of defoliation on morphological and chemical composition of the grazing layer of two warm‐season perennial grasses of contrasting structures (tall tufted grass—elephant grass, Exp. I; small size stoloniferous grass—kikuyu grass, Exp. II) under intermittent stocking management. The treatments were as follows: Exp. I—factorial arrangement between two pre‐grazing heights (90 and 120 cm) and two proportions of defoliation (removal of 50% or 70% of the initial pre‐grazing heights); Exp. II—four pre‐grazing heights (10, 15, 20 and 25 cm) combined with the same proportion of defoliation (50% of the initial pre‐grazing heights). Forage samples were collected at pre‐grazing heights and clipped into the grazing layer (cutting heights defined by treatments). The following variables were analyzed: (a) forage mass; (b) proportion of leaves, stems, and dead material; (c) crude protein, neutral detergent fiber, and acid detergent fiber contents. In a general way, there were no significant differences in morphological and chemical composition of the grazing layer of treatments with proportions of defoliation of 50%. Although the treatments of 70% (Exp. I) and 10 cm (Exp. II) showed some differences, both targets impaired the grazing process and were considered as unpractical under field situations. It was concluded that forage chemical composition of warm‐season perennial grasses does not change in the upper half of the sward within a range of pre‐grazing heights, provided moderate proportions of defoliation (around 50%) are used.

The morphogenetic and structural characteristics of forage plants and the processes of growth and senescence in tissues may

The milk and meat from animals with a pasture-based diet have higher proportions of CLA and C18:3 and lower omega-6:omega-3 ratios than products from animals with diets based on corn silage and concentrate. However, most of the published studies have evaluated fatty acid profiles in temperate climate grasses and the literature with tropical grasses is scarce. Thus, the aim of this study was to evaluate the morphological and fatty acid compositions in the vertical strata of elephant grass (Pennisetum purpureum Schum.) swards subjected to grazing heights (90 or 120 cm pre-grazing heights) and levels of defoliation (50% or 70% removal of the initial pre-grazing height). There were no interactions among pre-grazing height, the level of defoliation and grazing stratum. However, higher proportion of C18:3 (58% and 63%) was found in the 90-cm swards and in the half upper stratum. A higher proportion of C18:3 was associated with a higher leaf proportion and crude protein content. Thus, the upper stratum of sward or a grazing management scheme (e.g. first-last stocking) resulting in a higher proportion of leaves and crude protein both provide higher proportions of C18:3 to animals grazing in elephant grass swards.

Defoliation may play a role in source-

A aplicação de dessecantes pode influenciar na qualidade fisiológica das sementes de trigo e ainda não há herbicidas dessecantes recomendados para uniformizar a maturidade das lavouras. Objetivou-se neste trabalho avaliar a qualidade fisiológica das sementes de trigo cultivar CD 123, colhidas em diferentes estádios fenológicos e colorações dos grãos, provenientes de plantas submetidas à aplicação de duas doses de três herbicidas dessecantes em pré-colheita. O experimento foi conduzido em delineamento de blocos ao acaso, com quatro repetições, em esquema fatorial 7 x 4. Foram avaliados os dessecantes: carfentrazona etílica, glufosinato-sal de amônio e flumioxazina em duas doses de aplicação (recomendada e metade da dose recomendada) mais a testemunha totalizando 7 tratamentos e quatro graus de maturidade visual das espigas na colheita (estádio 89-verde, 89-madura, 91-verde e 91-madura). Os dados foram sumetidos à ANOVA e as médias comparadas pelo teste de Scott-Knott, a 5% de probabilidade. A aplicação do dessecante carfentrazona em dose cheia afetou negativamente a germinação das sementes colhidas de plantas no estádio fenológico 89 com coloração verde dos grãos. Os demais dessecantes quando aplicados em meia dose resultaram em maiores índices de germinação. A produçãos de sementes por planta não foi afetada pelos dessecantes e suas respectivas doses, tendo influência somente dos graus de maturidade, em que os grãos verdes resultaram em menor produção de sementes por planta. Sementes colhidas precocemente, ainda com coloração verde tem menor qualidade que as colhidas com a coloração típica madura. Os herbicidas glufisinato e flumioxazina (meia ou dose cheia) possibilitam colheita de sementes de qualidade e não afetam a o desempenho produtivo das plantas dessecadas.