The experiment took place at the Aquaponics Laboratory of the Department of Aquaculture from November 2024 to January 2025. Each of the 12 plastic tanks held approximately 300 litres, with about 200 litres of clean water added after cleaning. A 20-watt submersible pump circulated wastewater to a biological filter, while an 18-watt air pump and two stiff, perforated air stones supplied oxygen continuously. Treatments were assigned according to a completely randomized design: diets containing 0%, 3%, 6% or 9% papaya leaf meal, designated T0 through T3. Each tank was treated as an independent experimental unit, providing three replicates for each diet. Fish were acclimatized for seven days before the trial and stocked at a comparable biomass of about 400 grams per tank.

The fingerlings began with a mean total length of 8.47 ± 0.27 centimetres and a mean weight of 14.79 ± 0.70 grams. They were fed twice daily, at 9:00 a.m. and 5:00 p.m., with the daily ration set at 3% of body weight. Total length and body weight were measured at 15-day intervals. The researchers calculated weight gain, percentage weight gain, specific growth rate, feed conversion ratio, feed conversion efficiency, protein efficiency ratio, survival and production. Water quality was also checked every 15 days. At the end of the 60-day period, blood was analyzed for red and white blood cell counts, haemoglobin, glucose and mean corpuscular haemoglobin. One-way analysis of variance and Duncan’s Multiple Range Test were used to compare treatments at a significance level of p < 0.05.

Papaya leaves were collected beside the experimental site, separated from their branches and dried at 40°C for two days in a homemade dryer. The dried leaves were weighed, ground into fine powder and incorporated into the feed. Proximate analysis found that the meal contained 25.25% crude protein, 16.16% crude lipid, 22.53% crude fibre, 23.21% moisture, 11.2% ash and 24.86% carbohydrate. The experimental diets also contained fish meal, soybean meal, wheat bran, rice bran, mustard oil cake, vitamins and molasses. As PLM inclusion increased from 0% to 9%, soybean meal was reduced from 33% to 24%, while the other major ingredients and total crude protein remained similar. The four diets contained 34.73% to 35.12% crude protein. Fibre rose with PLM inclusion, from 4.20% in the control diet to 5.06% at 9% PLM.

The ingredients were mixed with molasses as a binder, processed into 2-millimetre pellets, sun-dried for two days and stored in airtight containers at 20°C. Differences were recorded in several growth and feed-performance measures. Fish receiving 9% PLM had a mean weight gain of 11.44 ± 0.48 grams, compared with 8.45 ± 1.01 grams in the control group, 9.07 ± 1.55 grams at 3% PLM and 10.32 ± 0.10 grams at 6% PLM. Percentage weight gain in the 9% treatment was 82.67 ± 2.07%, versus 57.44 ± 7.04% in controls. Specific growth rate was 1.06 ± 0.02% per day at 9% PLM and 0.69 ± 0.07% per day in the control diet, with the overall differences reported as statistically significant at p < 0.05.

Feed-performance measures showed a similar pattern. The 9% PLM group recorded the highest protein efficiency ratio, 1.28 ± 0.06, and feed conversion efficiency, 0.44 ± 0.02. It also had the lowest feed conversion ratio, 2.23 ± 0.10, indicating less feed was required per unit of wet weight gained than in the control group, where the ratio was 2.93 ± 0.23. Tank production at 9% PLM was 2.04 ± 0.02 kilograms per cubic metre over 60 days, compared with 1.55 ± 0.17 kilograms per cubic metre in controls. Production was 1.66 ± 0.12 and 1.83 ± 0.12 kilograms per cubic metre at 3% and 6% PLM, respectively. Protein intake did not differ significantly among treatments, nor did survival, which ranged from 85.24 ± 3.30% to 88.09 ± 6.60%.

Blood measurements differed among the dietary treatments. At the end of the trial, red blood cell counts in fish receiving 9% PLM averaged 3.10 ± 0.95 × 10^6 cells per cubic millimetre, compared with 2.20 ± 0.87 × 10^6 in controls. The corresponding values were 2.70 ± 1.33 × 10^6 at 3% PLM and 2.60 ± 1.46 × 10^6 at 6%. White blood cell counts were highest in the 9% treatment at 132.98 ± 2.26 × 10^3 cells per cubic millimetre, compared with 93.83 ± 2.44 × 10^3 in the control, 114.79 ± 2.8 × 10^3 at 3% and 103.351 ± 3.08 × 10^3 at 6%.

Haemoglobin concentration was 9.68 ± 0.61 grams per decilitre in controls and 12.15 ± 0.68 grams per decilitre in fish receiving 9% PLM. Glucose was lower in the 9% group, at 90 ± 2.3 milligrams per decilitre, compared with 113.33 ± 3.80 milligrams per decilitre in the control; the 3% and 6% groups recorded 92 ± 2.5 and 105.67 ± 3.88 milligrams per decilitre, respectively. Mean corpuscular haemoglobin did not differ significantly among diets. These results establish changes in the measured blood variables, but the experiment did not test disease resistance or use the blood measurements to demonstrate improved immune function in the fish.

Length and weight were strongly correlated within all four diets, with coefficients from 0.94 to 0.96. The regression exponents were 2.0549 for the control, 2.0526 at 3% PLM, 2.1286 at 6% and 2.1669 at 9%. Because each value was below 3, the analysis classified the observed growth as negative allometry, describing the relationship between length and mass during the trial. Water quality did not differ significantly among treatments and remained within the ranges described as suitable for tilapia. Mean temperature was 22.80°C, pH ranged from 6.95 to 7.34, dissolved oxygen ranged from 4.55 to 5.20 parts per million, and total dissolved solids ranged from 191.17 to 201.50 parts per million. Ammonia showed a slight upward trend toward the end of the trial but did not differ significantly among diets.

The proximate composition of the fingerlings also varied. Crude protein was highest in fish receiving 6% PLM, at 15.56 ± 0.04%, compared with 13.34 ± 0.01% in controls. The 9% PLM group had the highest crude lipid, 2.34 ± 0.02%, and ash, 3.67 ± 0.01%. The researchers discussed papain and other bioactive compounds in papaya leaves as possible contributors to improved protein digestion, while micronutrients were proposed as a possible influence on haemoglobin and cellular measurements. These mechanisms were interpretations rather than variables directly isolated by the experiment. Overall, the controlled results show that replacing part of the soybean meal with up to 9% papaya leaf meal improved several growth and feed-performance measures in the tested Nile tilapia fingerlings without a statistically detectable change in survival. Whether the same inclusion rate produces comparable results in longer trials, other production systems or commercial farms remains to be determined.

Subject of Research: Effects of dietary papaya leaf meal on growth and blood measurements in recirculating-system-reared Nile tilapia fingerlings

Article Title: Effect of Dietary Papaya (Carica papaya) Leaf Meal on Growth Performance and Haematological Responses of Nile Tilapia (Oreochromis niloticus) Fingerlings Reared in a Recirculating Aquaculture System

Article References: Farhad, F. B., Ritu, F. Y., Mustafi, M., Salam, M. A., & Hashem, S. (2026). Effect of Dietary Papaya ( Carica papaya ) Leaf Meal on Growth Performance and Haematological Responses of Nile Tilapia ( Oreochromis niloticus ) Fingerlings Reared in a Recirculating Aquaculture System. Veterinary Medicine and Science, 12(6), Article e71271. https://doi.org/10.1002/vms3.71271

Image Credits: AI Generated

DOI: 10.1002/vms3.71271

Keywords: Nile tilapia, papaya leaf meal, aquaculture feed, growth performance, feed conversion, blood parameters, recirculating aquaculture, plant-based feed, tank production, Effect, Dietary, Papaya