Caracterizações morfológica e agronômica e divergência genética em germoplasma de trevo-branco Agronomic and morphological characterizations and genetic divergence on white clover germplasm

Objetivou-se caracterizar a variabilidade existente e estimar a divergência genética de uma coleção nuclear de trevo-branco formada por 78 acessos. Dezessete plantas de cada acesso foram caracterizadas com base em nove parâmetros (oito morfológicos e um agronômico): estatura das plantas, hábito de crescimento, intensidade de florescimento, comprimento de estolão, número de nós por estolão, comprimento dos entrenós, diâmetro de estolão, produção total de MS e área foliar por planta. Pela estimativa da distância de Mahalanobis, os acessos 1 (PI 195534) e 10 (PI 419325) apresentaram a maior distância (45,4) e os acessos 58 (PI 180491) e 68 (PI 197830), a menor distância (0,19). A área foliar foi a característica com maior contribuição relativa para divergência genética (24%), seguida pela estatura da planta (20%), pela intensidade de florescimento (19%) e pela produção total de MS (15%). A análise de correlação linear simples entre as variáveis mostrou correlação positiva e significativa entre estatura e área foliar (0,92), assim como entre comprimento de estolão e comprimento de entrenós (0,90).<br>This work aimed to evaluate morphological features of the white clover core collection obtained from the United States Department of Agriculture (USDA), represented by 78 accessions, in order to characterize the existent morphological variability and to estimate the genetic divergence, using nine characters (eight morphological and one agronomic). Seventeen plants from each access were evaluated individually at the Experimental Station of the Universidade Federal do Rio Grande do Sul in Eldorado do Sul and characterized in relation to the following characters: plant height, growth habit, flowering intensity, stolon length, node number per stolon, internode length, stolon diameter, total dry matter yield and leaf area per plant. Using the estimate of Mahalanobis' distance, the results showed that the accessions 1 (PI 195534) and 10 (PI 419325) presented the greatest distance (45.4), while the accessions 58 (PI 180491) and 68 (PI 197830) presented the smallest distance (0.19). The leaf area was the character with the largest individual relative contribution to the genetic divergence (24%), followed by plant height (20%), flowering intensity (19%) and total dry matter yield (15%). There was a positive and highly significant correlation between plant height and leaf area (0.92) and also between stolon length and internode length (0.90)

Opportunities for telemetry techniques in studies on the nutritional ecology of free-ranging domesticated ruminants

The principles of domestic herbivore nutrition are well understood and have been developed through detailed physiological studies, although methods to accurately measure field-based intake still challenge herbivore nutrition research. Nutritional ecology considers an animal's interaction with the environment based on its nutritional demands. Although there are a number of theoretical frameworks that can be used to explore nutritional ecology, optimal foraging provides a suitable starting point. Optimal foraging models have progressed from deterministic techniques to spatially explicit agent-based simulation methods. The development of optimal foraging modelling points towards opportunities for field-based research to explore behavioural preferences within studies that have an array of nutritional choices that vary both spatially and temporally. A number of techniques including weighing animals, weighing herbage, using markers (both natural and artificial) and sampling forage, using oesophageal-fistulated animals, have been used to determine intake in the field. These intake measurement techniques are generally most suited to studies that occur over a few days and with relatively small (often less than 10) groups of animals. Over the last 10 years, there have been a number of advances in automated behavioural monitoring technology (e.g. global positioning systems) to track animal movement. A number of recent studies have integrated detailed spatial assessments of vegetation using on-ground sampling and satellite remote sensing; these data have been linked to behavioural preferences of herbivores. Although the recent studies still do not address nutritional interactions over months or years, they do point to methods that could be used to address landscape scale nutritional interactions. Emerging telemetry techniques used to monitor herbivore behavioural preferences and also to determine detailed landscape vegetation mapping provide the opportunity for future herbivore nutritional ecology studies