O incentivo ao consumo e à produção em grande quantidade na sociedade atual gera, exageros de resíduos sólidos urbanos que, em alguns casos, podem ser utilizados para a geração de energia. Neste sentido e visando reduzir os resíduos dos aterros municipais e gerar energia, buscou-se produzir briquetes com mistura de rejeitos de resíduos sólidos urbanos (RRSU) e resíduos de madeira de Eucalyptus grandis. Os briquetes foram fabricados com 0, 5, 10, 15, 20 e 25% de RRSU na mistura com resíduos madeireiros contendo 12% de umidade. Os parâmetros analisados para a escolha da melhor mistura, foram: análise de combustibilidade x cinzas, resistência e energia utilizável. Os briquetes com até 10% de RRSU se mostraram com baixa resistência e os acima de 15% apresentaram grande aumento no teor de cinzas; portanto, os que melhor atenderam aos requisitos combustibilidade x cinzas e resistência mecânica, foram aqueles com 15% de RRSU, pois não se conhece a procedência das cinzas. Considerando-se a energia utilizável, o briquete com 25% de RRSU é o que apresenta maior poder calorífico útil na ordem de 17.175 kJ kg-1 motivo pelo qual se indica a produção de briquetes com adição RRSU; ressalta-se, porém, a necessidade de estudos sobre a emissão de gases.

No abstract

a b s t r a c tThe objective of this work was to evaluate carbon turnover and half-life in feces and blood from sheep fed on C 3 and C 4 plant diets, using the stable isotope technique. Eight Santa Ines sheep were randomly distributed between two treatments: the first consisted of animals that were fed alfalfa hay, and the second consisted of animals that were fed corn silage only. Function of time was used to measure carbon turnover rate. At steady state, the half life for carbon isotopic enrichment between food and feces is 1.2 and 1.0 days for alfalfa hay and corn silage treatments, respectively. For blood data collection the time was insufficient to reach the isotope equilibrium level, indicating a slow carbon exchange between diet and blood. It is concluded that blood has a slow turnover, indicating the isotope signal for the former diets. Feces, by contrast, have a quick turnover, indicative of their recent diets.

Stable isotope analyses have helped in assessing dietary switches if the diet undergoes metabolic alteration (isotopic exchange). However, when considering the effects over time of switching from one diet to another, one can assess how quickly the new diet is incorporated into tissues via the isotopic renewal or incorporation rate, or turnover. Turnover is obtained using exponential curves that fit the original data, allowing the determination of practical order parameters such as the half-life (T) and the turnover constant (k). Researchers have found that metabolic incorporation can be fractionated. The resulting fractions, called metabolic pools, are identified using the linearization of the isotopic exchange model and its linear fit. This fractionation methodology is still not well defined. The objective of this study was to assess the behaviour of the metabolic renewal rate (turnover) in fractionated form, explain the theory, and apply it to data from the avian duodenal mucosa and albumen. We concluded that the duodenal mucosa has one metabolic pool, with a half-life of 1.23 days, and that the albumen has two metabolic pools, with half-lives of 1.89 and 6.32 days.

The objective of the study was to evaluate body growth and age at onset of puberty on lambs fed two specific diets for low and high growth rates. A herd of 20 Brazilian Bergamasca lambs was divided in two groups (n= 10) and kept confined throughout the experimental period, two animals of the same treatment/pen. Two phases were established: Phase 1, from 90 days of age until the onset of puberty; and Phase 2, from puberty onset up to 1 year old. For Phase 1, two distinct diets were formulated, being: Treatment A, which was formulated to obtain an average daily gain of approximately 150g; and Treatment B, for an average daily gain of about 250g. In Phase 2, a balanced, equal diet was provided to both groups. Every 14 days, the animals were weighed and given average daily gain, average daily dry matter intake and body condition score. From the 5 th month of age on, in each group, a vasectomized male was used to detect estrus, establishing age at puberty onset and estrus interval for each lamb. Blood samples were collected every 28 days to determine plasma growth hormone concentration. Treatment B lambs gained more weight and had higher body condition score (P<0.05) and there was no difference for age at puberty onset and plasma growth hormone levels (P>0.05) between treatments. It was found that both treatments showed satisfactory performances. Thus, treatment A may be indicated as a reasonable feeding system to achieve positive responses on confined ewe lambs during growth phase.