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Effects of days-fasting and refeeding on growth, biochemical and histometric liver parameters in pacu Piaractus
K N N Farias1,2, A L N Silva1,2, T V Silva1,2
1Universidade Federal de Mato Grosso do Sul - UFMS, Faculdade de Medicina Veterinária e Zootecnia, Programa de Ciência Animal, Campo Grande, MS, Brasil.
Insights
Fasting and refeeding pacu (Piaractus mesopotamicus) did not impact fish growth. However, a 50-day refeeding period may enhance compensatory growth in pacu, offering insights for aquaculture feeding practices.
Area of Science:
- Aquaculture and Fish Physiology
- Nutritional Studies in Aquatic Organisms
Background:
- Understanding the physiological impacts of nutritional strategies is crucial for optimizing aquaculture.
- Pacu (Piaractus mesopotamicus) is an important freshwater fish species in aquaculture, requiring efficient feeding management.
Purpose of the Study:
- To evaluate the effects of a 30-day fasting period followed by 50 days of refeeding on growth, biochemical, and hepatic parameters in juvenile pacu.
- To determine the recovery potential and compensatory growth of pacu after a period of nutritional deprivation.
Main Methods:
- Juvenile pacu were subjected to a 30-day fasting period followed by 50 days of refeeding, with a control group fed continuously.
- Biometric parameters (weight, relative condition factor, hepatosomatic index), liver assessments (hepatocyte density, nuclear volume, glycogen), and plasma biochemical parameters were measured.
- Sampling occurred at multiple time points during both fasting and refeeding phases.
Main Results:
- Fasting significantly reduced hepatocyte density, liver glycogen, and hepatocyte nuclear volume, while increasing cholesterol, blood vessel, and sinusoidal density.
- The relative condition factor remained unchanged during fasting.
- After refeeding, all measured parameters returned to control levels, with the hepatosomatic index being significantly higher on day 50 of refeeding.
Conclusions:
- Fasting followed by refeeding did not negatively affect overall growth in pacu.
- A 50-day refeeding period appears sufficient for physiological recovery and may promote compensatory growth in pacu.
- These findings provide valuable insights for developing effective feeding strategies in pacu aquaculture.
Abstract:
This study evaluated the effects of days-fasting followed by days-refeeding on growth, biochemical, and hepatic parameters in pacu (Piaractus mesopotamicus). One hundred and twenty juveniles P. mesopotamicus with initial average weight and length of 47.7 ± 9.2 g and 13.4 ± 0.9 cm were randomly distributed into six experimental units (20 fish per unit) and subjected to treatments: 30 days-fasting followed by 50 days-refeeding, and control group, fed continuously throughout the period. During the fasting period, samples were collected at 10, 20, and 30 days, while during the refeeding period at 15 and 50 days. Animals in the control group were sampled at the same periods. Weight (g), relative condition factor (Kn), and hepatosomatic index (biometric parameters) were measured. Liver assessments were performed. Additionally, glucose, plasma biochemical parameters levels were measured. After 30 days of fasting, hepatocyte density (73.8 ± 1.09%), liver glycogen (14.9 ± 0.87%) and hepatocyte nuclear volume (27.3 ± 0.30 µm3) were lower compared to the control group (82.0 ± 0.67%, 19.4 ± 0.74% and 43.40 ± 0.48 µm3 respectively). The relative condition factor remained unchanged. Cholesterol values, blood vessels, and sinusoidal density increased significantly during fasting. After refeeding, parameters were restored to the control level. On the 50th day of refeeding, the hepatosomatic index was significantly higher than the control group. The results showed that fasting associated with refeeding did not affect fish growth. The period over 50 days of refeeding may influence the pacu's compensation compared to daily-fed animals. The effects of fasting and its relationship with the pacu's physiological response through nutritional status become useful in contributing to feeding practices in P. mesopotamicus fish farming.
