Caracterização morfogênica e estrutural comparativa de cultivares de gramíneas forrageiras tropicais sob crescimento livre

Understanding of the morphogenetic characteristics allows comprehension of aspects related to the form and function of forage plants, providing opportunities to identify potentially high productive plants and distinct defoliation management requirements. The objective of this experiment was to carry out a comparative study of ten tropical forage grasses using morphogenetic and structural variables. Treatments corresponded to grasses of the Panicum genus (P. maximum cultivars Tanzânia and Mombaça) and the Brachiaria genus (B. brizantha cultivars Piatã, Marandu, Xaraés, Capiporã and Arapoty; B. decumbens cultivar Basilisk; B. humidicola cultivars Comum and Tupi), evaluated under free growth conditions.. Response variables were leaf appearance and elongation rates, phyllochron, stem elongation rate, final leaf length, number of live leaves per tiller, leaf life span and tiller appearance, death and survival rates. There was difference between cultivars for these variables, indicating a large variability within plants. Considering the morphogenetic and structural variables of leaves and tillers, B. brizantha had a similar pattern of variation to those of P. maximum, and B. Decumbens, similar to those of B. humidicola. Tiller appearance was large at the onset of the experiment and second and third generations comprised the large majority of tiller population for the cultivars Mombaça, Tanzânia, Xaraés and Capiporã. Group analysis based on plant morphogenetic and structural characteristics of leaves and tillers was an interesting way of grouping cultivars, indicating the importance and the potential of using morphogenesis in plant selection and evaluation programmes.O estudo das características morfogênicas permite compreender aspectos relativos à forma e função das plantas forrageiras além de possibilitar identificar plantas com potenciais produtivos e exigências de manejo diferentes. O objetivo deste trabalho foi avaliar, comparativamente, dez plantas forrageiras tropicais por meio de variáveis morfogênicas e estruturais. Os tratamentos corresponderam a cultivares pertencentes ao gênero Panicum (P. maximum cvs. Tanzânia e Mombaça) e ao gênero Brachiaria (B. brizantha cvs. Piatã, Marandu, Xaraés, Capiporã, e Arapoty; B. decumbens cv. Basilisk; B. humidicola cvs. Comum e Tupi), avaliados sob condições de crescimento livre. Foram avaliadas a taxa de aparecimento e alongamento de folhas, filocrono, taxa de alongamento de colmos, comprimento final da lâmina foliar, número de folhas vivas por perfilho, duração de vida das folhas e padrão demográfico de perfilhamento. Houve diferença entre cultivares para as variáveis, indicando grande variabilidade no material estudado. Considerando as características morfogênicas e estruturais de folhas e perfilhos, as B. brizantha apresentaram comportamento parecido com os P. maximum, e B. decumbens mais próximo das B. humidicola. Verificou-se que o aparecimento de perfilhos foi inicialmente elevado e que a segunda e, ou, terceira gerações contribuíram de forma significativa para o número total de perfilhos dos cultivares Mombaça, Tanzânia, Xaraés e Capiporã. A análise de agrupamento baseada nas características morfogênicas e estruturais de folhas e perfilhos foi um método interessante para agrupar cultivares, demonstrando a importância e o potencial de uso da morfogênese em trabalhos de seleção e avaliação de plantas forrageiras.FAPEMIGFederal University of Viçosa - Animal Science Departmen

Sward structure and livestock performance in guinea grass cv: Tanzania pastures managed by rotational stocking strategies

Grazing strategy is a key element in the determination of sward structure, herbage nutritive value and animal performance. We aimed to compare the herbage characteristics and performance of livestock in pastures of Panicum maximum cv. Tanzania managed, using two rotational stocking strategies, which provided either a fixed-length rest period (FRP) of 35 days in the spring and fall and 30 days in the summer, or a variable-length rest period (VRP), determined by the time required for the canopy to achieve 70 cm in height. The pastures were evaluated in the pregrazing condition for forage mass (FM); leaf (LP), stem (SP) and dead matter (DP) percentages; and nutritive value (NV). The animals were weighed every 28 days. Pastures managed with the FRPs exhibited greater FMs, SPs and DPs and lower LPs and NVs than those managed with the VRPs. The average daily livestock weight gain was greater during the spring and summer for the VRP than for the FRP pastures, resulting in an average animal weight gain per area of 990 and 860 kg ha−¹ wet period−¹ for the pastures managed with the VRPs and FRPs, respectively. Thus, pasture rest periods that were maintained after the sward reached 70 cm in height reduced the animal performance on Tanzania guinea grass

Sward structure and livestock performance in guinea grass cv: Tanzania pastures managed by rotational stocking strategies

Grazing strategy is a key element in the determination of sward structure, herbage nutritive value and animal performance. We aimed to compare the herbage characteristics and performance of livestock in pastures of Panicum maximum cv. Tanzania managed, using two rotational stocking strategies, which provided either a fixed-length rest period (FRP) of 35 days in the spring and fall and 30 days in the summer, or a variable-length rest period (VRP), determined by the time required for the canopy to achieve 70 cm in height. The pastures were evaluated in the pregrazing condition for forage mass (FM); leaf (LP), stem (SP) and dead matter (DP) percentages; and nutritive value (NV). The animals were weighed every 28 days. Pastures managed with the FRPs exhibited greater FMs, SPs and DPs and lower LPs and NVs than those managed with the VRPs. The average daily livestock weight gain was greater during the spring and summer for the VRP than for the FRP pastures, resulting in an average animal weight gain per area of 990 and 860 kg ha−¹ wet period−¹ for the pastures managed with the VRPs and FRPs, respectively. Thus, pasture rest periods that were maintained after the sward reached 70 cm in height reduced the animal performance on Tanzania guinea grass