Aditivos enzimáticos na dieta de tilápias do nilo e peixe ornamental

Abstract

Enzyme additives may be included in fish feed to aid the action of pancreatic enzymes such as amylase, protease and lipase, or can increase the uptake of previously unavailable nutrients by the absence of specific enzymes to degrade the physical barriers of fibrous components of the cell wall, especially the non-starch polysaccharides. The objectives of this work were to evaluate the influence of enzymatic additives composed of alpha-amylase, protease and phytase on the performance, carcass quality, ammonia excretion rate and glycemic curve of Nile tilapia, besides evaluating these enzymatic additives in the valorization of diets with high proportion of vegetable ingredients and reduction till to 2.64% in recommended levels of protein and energy and implications on performance and body composition of Nile tilapia. Also, included in the scope of this work was a study on the influence of the inclusion of the same enzymes on the performance of guppy ornamental fish. The experimental tests were carried out at the Aquaculture Laboratory of the UFPB / CCHSA. In order to evaluate the efficiency of the digestive enzyme blend on growth, body composition (chapter 2), glycemic curve and ammonia excretion as indicators of exogenous enzyme activity (chapter 3), five on top diets were elaborated: DCblend1 (DC + 100ppm phytase + 200ppm protease); DCBlend2 (DC + 100ppm phytase + 400ppm protease); DCBlend3 (DC + 200ppm phytase + 200ppm protease + 133ppm alpha-amylase); and DCBlend4 (DC + 200ppm phytase + 400ppm protease + 200ppm alpha-amylase). Enzymatic supplementation with DCBlend4 allowed higher final weight, weight gain and specific growth rate. The glycemic curves of the blood of the Nile tilapia, during 24 hours, suggest a higher absorption of glucose in the first 4 hours in the post feeding period in all evaluated treatments. Ammonia excretion peaks were observed at 2 h, 4 h and 8 h after feed supply, in diets supplemented with exogenous enzymes, probably related to the higher availability of protein. These data suggest that supplementation of on-top diets with exogenous protease and amylase enzymes may increase blood glucose concentrations and ammonia excretion rate and compromise carcass and water qualities in production systems. The next experiment was carried out to test the supplementation of the same enzymatic blends in diets with reductions of 1.32 and 2.64% of both protein and energy levels recommended. The performance and physical-chemical composition of tilapia kept at xviii sub-optimal temperature (23.15 ± 0.2ºC) were evaluated. Four diets were elaborated: Diet control "on top" (DC); Diet 2 (DC + enzyme supplementation); Diet 3 (reduction in 1.32% in CP and digestible energy - ED + enzymatic supplementation); and Diet 4 (reduction in 2.64% in CP and ED + enzyme supplementation). The enzymatic supplementation was efficient in providing nutrients supplying the deficit of up to 2.64% in PB and ED in the diet of tilapia submitted to sub-optimal temperature, since there were no differences between the parameters of weight, feed conversion, height and body width of fish. To evaluate the influence of enzymatic supplementation on the performance of guppy ornamental fish, two diets were tested, one of which was supplemented with the exogenous protease, phytase and alpha-amylase enzymes. Enzymatic supplementation positively influenced the growth and development of ornamental guppy fish. It is recommended the addition of preparations with the exogenous enzymes phytase, protease and especially alpha-amylase in diets with defict of 2.64% of protein and digestible energy due to improving the gain in growth and development of Nile tilapia and guppy fish.