Intestinal responses in pacu (Piaractus mesopotamicus) exposed to fasting and refeeding nutritional management

Fasting is a practice in the aquaculture industry that aims to reduce feed costs. This practice can affect the gastrointestinal system of fish. The intestine plays a pivotal role in the nutrition and overall health of fishes. The present study sought to evaluate the effects of fasting and refeeding on body weight, intestine somatic index (ISI), intestinal histometry (area, height, and thickness of the villi), and goblet cell volume (acidic and neutral mucins) of pacu (Piaractus mesopotamicus). To this end, the effects of 10, 20, and 30 days of fasting and 15 and 50 days of refeeding were evaluated. The results demonstrated that fasting resulted in notable alterations in all assessed parameters. The body weight and ISI of fasted pacu were significantly reduced compared to those of the control group. The levels of acidic and neutral mucins were elevated after 10 days of fasting, whereas the area and height of the villi decreased after 20 days of fasting. Following the 15-day refeeding period, pacu exhibited an increase in body weight and ISI. However, a 50-day refeeding period was required to observe an increase in villus height, which differed from that in the control group. After 50 days of refeeding, the fish exhibited intestinal conditions that were restored to the levels observed in the control specimens. Feed deprivation alters intestinal biometry and histomorphology. However, the effects of fasting were attenuated and even improved with subsequent refeeding. These results suggest that a fasting/refeeding management strategy is appropriate for pacu farming.