EFEITOS DA RESTRIÇÃO ALIMENTAR E REALIMENTAÇÃO SOBRE PARÂMETROS BIOMÉTRICOS, BIOQUÍMICOS E MORFOLÓGICOS EM PACU (Piaractus mesopotamicus)

Abstract

In the fish sector, food is one of the most expensive inputs within the production system, due to which some work has been carried out with the implementation of the technique of food restriction and later the refeeding, with the intention of reducing the costs with the feed. In this technique, the restriction adjustments associated with the return of feeding provide compensatory growth responses, due to the food offer, suppressing the appetite of these specimens. However, in response to this management, the fish show body changes with the absence of food. Therefore, this work was carried out with the objective of evaluating the effects of total food restriction (10, 20 and 30 days) and refeeding (15 and 50 days) in Piaractus mesopotamicus on biometric parameters (weight, hepatosomatic index, relative condition factor Kn, and somatic intestine index), structural density (%) (hepatocytes, sinusoids, blood vessels and liver glycogen), liver histometry (hepatocyte volume and hepatocyte nuclear volume), plasma biochemistry (glucose, cholesterol and triglycerides), intestinal histometry (area, height, and thickness of the villus), and volume of goblet cells (acidic and neutral mucins). For biometric and biochemical analysis, 12 fish were used, and six fish for other analyses, for each treatment/group. The fish were standardized with an initial weight of 47.7 ± 9.0 g. Necropsy of the specimens was performed to remove liver fragments (weighing (g) and determination of the hepatosomatic index (%)), and intestine fragments (weighing (g) and determination of the somatic intestine index (%)) that were processed by the histological technique. For structural volumetric density, and histometric evaluations were prepared on hematoxylin and eosin (H&E) staining. For analysis of hepatic glycogen density, samples were stained with Periodic Acid Schiff. Histometric evaluations were performed using the Motic Plus 2.0 program. Plasma biochemistry was measured by a COBASS automation device. To determine the volume of goblet cells, the slides were stained with periodic acid Schiff (neutral mucins) and alcian blue (acidic mucins) also evaluated in Motic Plus 2.0. Total food restriction showed changes in virtually all evaluated parameters. With reduced body weight, hepatosomatic index, and intestine somatic index (P<0.05), and no change in relative condition factor Kn. Density of hepatocytes and liver glycogen were lower, while blood vessels and sinusoids increased (P<0.05). For liver histometry; hepatocyte volume, and hepatocyte nuclear volume decreased (P<0.05). Glucose and triglyceride values decreased, while cholesterol increased (P<0.05). For intestinal histometry; the villus area and height showed a reduction only after 20 days of restriction, and the values of acidic and neutral mucins increased (P<0.05) at 10 days of restriction, being subsequently reduced. With refeeding, the weight of the fish at 50 days was similar to the weight of the control animals, showing total compensation (P>0.05). Hepatosomatic index values increased at 15 days, being similar to the control, while somatic intestine was higher than the control (P<0.05). Hepatocyte density and liver glycogen were restored at 50 days (P>0.05). Blood vessels and sinusoids were similar to the control after 15 days of refeeding. On histometry, hepatocyte volume and hepatocyte nuclear volume increased (P>0.05). Glucose, triglycerides and cholesterol parameters returned to normal. The height of the intestinal villus increased at 50 days of refeeding (P<0.05). Therefore, it is concluded that Piaractus mesopotamicus on food restriction for a prolonged period of 30 days showed alterations in the biometric, biochemical, and liver and intestines parameters of the histological , without affecting the well-being of the specimens, but suggestive of a reduction in intestinal absorption, inferring immunoinflammatory responses by the intestinal microbiota, influencing the increase in the volume of acidic goblet cells. The refeeding for a period of up to 50 days verified the adaptation of the pacu, through the reestablishment of the evaluated parameters and the total compensation, even after a long period of restriction.