Temperature and dehydration effects on metabolism, water uptake and the partitioning between respiratory and cutaneous evaporative water loss in a terrestrial toad.

Terrestrial anurans often experience fluctuations in body temperature and hydration state, which are known to influence evaporative water loss through the skin (EWLSkin) and lungs (EWLResp). These effects arise from associated changes in skin permeability, metabolism and lung ventilation. Herein, we determined the rates of EWLSkin and EWLResp in the terrestrial toad Rhinella diptycha at different temperatures and hydration states. We measured oxygen uptake rates to verify whether alterations in the partitioning between EWLSkin and EWLResp were associated with metabolism-induced changes in pulmonary gas exchange. We also measured the influence of hydration and temperature on water uptake (WU) through the skin. Finally, as estimates of skin resistance to evaporation (Rs) are usually inferred from total evaporative water loss (EWLTotal), under the assumption of negligible EWLResp, we calculated the potential error in accepting this assumption for different temperature and hydration states. EWLSkin and EWLResp increased with temperature, but this response was greater for EWLResp, which was attributed to the temperature-induced elevation in metabolism and lung ventilation. Dehydration caused a decrease in the relative contribution of EWLSkin to EWLTotal, mirrored by the concurrent increase in the contribution of EWLResp, at all temperatures. Thus, Rs increased with dehydration. WU rates were dictated by dehydration with little influence of temperature. The partitioning between EWLSkin and EWLResp was affected by both temperature and hydration state and, under some conditions, considering EWLResp as negligible led to significant errors in the assessment of skin resistance to evaporation.

Suplementacao de zinco orgânico na racão de frangos de corte alojados em cama nova ou reutilizada / Organic zinc supplementation in the diet of broilers housed in new or reused litter bedding

Vários fatores podem interferir no desenvolvimento do frango de corte, dentre eles podemos destacar a nutrição e o manejo. No contexto nutricional, a suplementação mineral é uma prática necessária, pois, de modo geral, as dietas não contêm esses elementos em quantidade suficientes para atender as necessidades das aves. O zinco é um micromineral essencial à vida, participando de várias funções importantes ao organismo. Geralmente o zinco é adicionado a dietas das aves nas formas inorgânicas (oxidos, sufatos ou carbonatos), entretanto em sua forma orgânica ou quelatada apresenta-se mais biodisponível. Objetivou-se com o presente estudo avaliar o efeito dos níveis de zinco orgânico (ZnO) na ração de frangos de corte de 1 a 42 dias, alojados em cama nova ou reutilizada. O experimento foi conduzido no setor de avicultura da Unidade Especializada em Ciências Agrárias da EAJ/UFRN. Foram utilizados 576 pintos de 1 dia da linhagem comercial Cobb, distribuídos em delineamento inteiramente casualizado em esquema fatorial 4x2 com quatro níveis de ZnO 0; 40; 80 e 120 ppm e dois ambientes, cama nova (CNo) e cama reutilizada (CRe), resultando em 8 tratamentos com 6 repetições de 12 aves. Na fase pré-inicial houve efeito linear crescente dos níveis de ZnO sobre o consumo de ração e efeito quadrático sobre o peso vivo e o ganho de peso. Os níveis de 72,41 e 70,05 ppm de ZnO na ração de pintos melhoraram o peso vivo e o ganho de peso, respectivamente. Houve interação entre ZnO e o tipo de cama utilizada. O ZnO não afetou o desempenho das aves na fase de crescimento. Houve interação entre os níveis de ZnO e o tipo de cama utilizada. Os níveis de 61,50 e 85,30 ppm de zinco orgânico melhora a imunidade e aumenta a deposição de zinco na tíbia de frangos de corte aos 42 dias, respectivamente. O ZnO também aumenta a resistência de pele dos frangos aos 42 dias de idade. O uso de CRe melhora o desempenho de frangos de corte de 1 a 42 dias de idade.

Abstract: Several factors can affect the development of the broiler, among them we can highlight nutrition and management. In the context nutritional, mineral supplementation is a necessary practice because, in general, the diets did not contain these elements in sufficient quantity to meet the needs of poultry. Zinc is a trace mineral essential to life, participating in several important functions in the body. Generally zinc is added to diets of birds in inorganic forms (oxides, carbonates or sufatos), however in its organic form or chelated presents more bioavailable. The objective of this study was to evaluate the effect of levels of organic zinc (ZnO) in the diet of broilers from 1 to 42 days, housed in new or reused litter. The experiment was conducted in the poultry sector of the Special Unit for Agricultural Sciences EAJ / UFRN. 576 chicks were used 1 day of commercial strain Cobb, distributed in a completely randomized in a 4x2 factorial arrangement with four levels of ZnO 0, 40, 80 and 120 ppm and two environments, new bed (COn) and reused litter (CRE) resulting in eight treatments with six replications of 12 birds. In the pre-initial responses were linearly increasing levels of ZnO on feed intake and quadratic effect on body weight and weight gain. The levels of 72.41 and 70.05 ppm of ZnO in the diet of chicks improved body weight and weight gain, respectively. There was interaction between ZnO and the type of bedding used. The ZnO did not affect broiler performance in the growing phase. There was an interaction between levels of ZnO and type of bed used. The levels of 61.50 and 85.30 ppm organic zinc improves immunity and increases the deposition of zinc in tibia of broilers at 42 days, respectively. ZnO also increases the resistance of the skin of broilers at 42 days of age. Using Cre improves performance of broilers from 1 to 42 days old.