The mineral consumption and weight gain of grazing steers fed mineral supplements with different sodium contents and physical forms Consumo mineral e ganho de peso de garrotes mantidos em pastoreio recebendo suplementos minerais com diferentes teores de sódio e formas de apresentação

Thirty crossbred two-year-old steers, kept on pasture of Braquiaria decumbens, were used in two different experiments of 90 days each. In the first experiment, the steers were randomly assigned in five groups of six steers each to verify the influence of different percentages of sodium chloride (SC) in mineral mix (MM) containing essential macro and microelements (A - 100% SC; B - 80% SC/20% MM; C - 60% SC/40% MM; D - 40% SC/ 60 MM and E - 20% SCl/80 MM) on the consumption of the mineral supplement and the weight gain. In the second experiment, the same steers were reassigned to three groups of 10 animals each to study the effect of mineral salt (40% SC/60% MM) offered loose, partially blocked or as a hard block on the mineral consumption and weight gain. Steers fed supplement D had the highest intake followed by groups B and C; lowest intake was verified in group E. All mineral supplements but E were fed adequately to meet the Na requirement (6.3g/head/d) for a 350kg growing steer. Higher average daily gain was verified in steers of groups D and C than those of group E. The highest mineral intake was observed in steers fed loose mineral (60g/head/d) followed by partially block (45g/d); the lowest consumption occurred in the steers fed hard block mineral (27g/d). The coefficient of variation of supplement intake increased as mineral hardness increased. The higher the mineral intake, in the second experiment, the greater the average daily gain. Grazing steers should be offered mineral supplements with 40% and 60% of NaCl changed weekly in order to avoid the hardening of its contents.<br>Trinta garrotes cruzados, com dois anos de idade, mantidos em pastos de capim Braquiria decumbens, foram utilizados em dois experimentos, com duração de 90 dias cada. No primeiro deles, os garrotes foram distribuídos, ao acaso, em cinco grupos de seis animais cada, para avaliar a influência de diferentes porcentagens de cloreto de sódio (CS) na mistura mineral (MM), contendo os principais macro e microelementos essenciais, (A - 100% CS; B - 80% CS/20% MM; C - 60% CS/40% MM; D - 40% CS/ 60% MM; E - 20% CS/80% MM) sobre o consumo de suplemento mineral e o ganho de peso, no período. No segundo experimento, os mesmos garrotes foram redistribuídos, ao acaso, em três grupos de 10 animais cada, para verificar a influência da oferta de suplemento mineral na forma solta, parcialmente empedrado ou totalmente empedrado, sobre o consumo deste alimento e sobre o ganho de peso, no período. No primeiro experimento, maior ingestão de suplemento foi detectada no grupo recebendo a fórmula D, seguida pelas fórmulas B e C; menor ingestão ocorreu nos garrotes que receberam o suplemento E. Com exceção deste último grupo, o suplemento mineral dos demais foi ingerido adequadamente para suprir o requerimento diário de sódio (6,3g/cabeça) de um garrote de 350kg. Maior ganho de peso médio diário foi constatado em garrotes dos grupos D e C, comparados com os do grupo E. No segundo experimento, maior ingestão de suplemento ocorreu em garrotes que receberam mineral solto (60g/cabeça/dia), seguido pelos que ingeriram sal mineral parcialmente empedrado (45g/dia); o menor consumo foi constatado nos garrotes para os quais foram ofertados suplemento empedrado (27g/dia). O coeficiente de variação da ingestão do suplemento mineral, pelos garrotes, aumentou quanto maior foi o grau de empedramento do sal oferecido. Quanto maior foi a ingestão de suplemento mineral, ofertada aos garrotes no segundo experimento, maior foi o ganho de peso constatado. Os dados obtidos permitem concluir que garrotes em pastoreio devem receber suplementos minerais contendo 40% a 60% de cloreto de sódio nas suas fórmulas, e que os mesmos devem ser reabastecidos semanalmente, nos cochos, a fim de evitar o empedramento de seus conteúdos

Microbe-aliphatic hydrocarbon interactions in soil: implications for biodegradation and bioremediation.

Aliphatic hydrocarbons make up a substantial portion of organic contamination in the terrestrial environment. However, most studies have focussed on the fate and behaviour of aromatic contaminants in soil. Despite structural differences between aromatic and aliphatic hydrocarbons, both classes of contaminants are subject to physicochemical processes, which can affect the degree of loss, sequestration and interaction with soil microflora. Given the nature of hydrocarbon contamination of soils and the importance of bioremediation strategies, understanding the fate and behaviour of aliphatic hydrocarbons is imperative, particularly microbe-contaminant interactions. Biodegradation by microbes is the key removal process of hydrocarbons in soils, which is controlled by hydrocarbon physicochemistry, environmental conditions, bioavailability and the presence of catabolically active microbes. Therefore, the aims of this review are (i) to consider the physicochemical properties of aliphatic hydrocarbons and highlight mechanisms controlling their fate and behaviour in soil; (ii) to discuss the bioavailability and bioaccessibility of aliphatic hydrocarbons in soil, with particular attention being paid to biodegradation, and (iii) to briefly consider bioremediation techniques that may be applied to remove aliphatic hydrocarbons from soil