Detoxificação de farelos de crambe e tungue e avaliação na resposta nutricional do jundiá (Rhamdia quelen)

Abstract

The vegetable meals are pointed out as the main alternative sources of the protein with widespread availability, low cost and nutritional potential to replace the fish meal in aquaculture diets. However, they have lower protein content, higher fiber and antinutrients, requiring a thorough study for broad and secure applicability. Processing techniques or pretreatment may extract and/or inactivate antinutrients improving the nutritional value of the sources. In this sense, we measured nutrients and antinutrients and dynamics of in vitro protein digestibility of tung and crambe meal in nature and after chemical treatment in acid-alcohol solution. This procedure reduced the levels of fat, calcium, phosphorus, condensed tannins and phytic acid in tung meal, increased neutral detergent fiber and did not change crude protein, ash, phenolic compounds, total and hydrolysable tannins. For crambe meal the treatment increased the fiber and ash contents and reduced crude protein, fat, calcium, phosphorus, total phenols, tannins (total, hydrolysable and condensed) and phytic acid. However, there was no effect of chemical treatment on the in vitro protein digestibility of the meals. The crambe or tung meals were also pretreated with exogenous microbial enzymes, non-commercial phytase (phytase and tannase action 1400 U and 1100 U/Kg) and commercial phytase (Natuphos/BASF, 1400 U/Kg). The commercial phytase showed higher efficiency on the tung meal, reducing phytic acid concentration and non-commercial phytase acted more effectively on the tannins in crambe meal. The replacement of fish meal and meat and bone meal by in natura crambe or tung meal (integral form) or chemically or enzymatically detoxified in feeding of silver catfish (Rhamdia quelen) was evaluated for nine weeks, with the study of growth, digestive parameters, metabolic and body nutrient deposition. Growth response similar to the control was observed since the beginning of the study in animals fed with crambe meal in the integral or chemically detoxified forms. These animals showed minimal enzymatic and metabolical changes. The inclusion of integral tung meal or chemically detoxified caused slower growth of animals. In the diet containing the integral form of meal, these results were observed until the end of the experimental period and were summed the lower digestive enzymatic and metabolic changes and lower survival of the animals. Tung meal chemically treated caused greater growth compared to the integral form, possibly due to removal of antinutrients and toxic substances. The inclusion of vegetable meals (both forms of enzymatically treatment) reduced fish growth since the first evaluation, but the response was more pronounced in animals that received tung meal. The increase in the digestivosomático index and intestinal quotient can demonstrate a physiological adaptation of these animals to the consumption of diets with tung meal, which showed the highest fiber content. With regard to body composition, ash, crude protein and phosphorus were not changed between treatments containing vegetable meals under study, but treatments with inclusion of tung meal provided lower dry matter and fat content in animals.