Níveis de energia para matrizes de tartaruga (Podocnemis expansa, Schweigger, 1812) em cativeiro no Amazonas

Abstract

The commercial farming of chelonians is permitted under IBAMA Normative Instruction No. 07/2015. Animal nutrition is a key factor for the success of such enterprises. This study aimed to evaluate the effects of dietary gross energy (GE) and crude protein (CP) levels in diets for breeding females and males of the Amazon river turtle (Podocnemis expansa) raised in captivity in the state of Amazonas, Brazil. This was initially conducted through a diagnostic assessment of reproductive indices and feeding practices of P. expansa across 20 commercial farms in Amazonas, based on annual reports from 2004 to 2024 provided by IBAMA and the Wildlife Laboratory of the Federal University of Amazonas. In addition, a field experiment was performed to test the influence of different dietary GE levels (3,900 and 4,600 kcal/kg) on productive and reproductive performance, offspring development, and biochemical profiles of captive breeders. Retrospective data (2004–2024) from 20 licensed farms, comprising a total of 131,127 breeding females (374.65 ± 287.46 females/farm/year), indicate that more than 2,240 clutches and 139,000 hatchlings were produced. Dietary GE levels ranged from 2,275 to 4,337 kcal/kg, while CP ranged from 25 to 45%. All producers (100%) used commercial fish feed supplemented with coproducts or by-products. Mean female body weight was 24.4 ± 7.1 kg. Reproductive parameters included 2,240 nests (mean = 14.4 nests/farm/year), 92.9 ± 14.3 eggs per nest, 139,427 hatchlings (mean = 911.3 ± 2,542.5 hatchlings/farm/year), a hatching rate of 62.9 ± 26.9%, and 60.1 ± 26.8 hatchlings per nest. Positive correlations were observed between female body weight and the number of nests, eggs, and hatchlings. Diets containing moderate GE levels (3,000–3,900 kcal/kg) and CP levels (30–39%) were associated with improved body weight (26.7 kg), mean number of nests (24.9), eggs (2,342), hatchlings (1,793), nest productivity (7.8%), and hatchlings per female (5.5 hatchlings/female/year). However, the highest hatching rates (68.9 ± 18.2%) and hatchlings per nest (67.9 ± 21.5) were observed at lower GE (2,250–2,900 kcal/kg) and CP levels (25–29%). The field trial was conducted at Fazenda Bicho do Rio, located at km 26, AM-070 highway, Iranduba, Amazonas. Two diets were evaluated: T0 – Nutripiscis feed (28% CP; 3,900 kcal/kg GE) and T1 – Multifós feed (28% CP; 4,600 kcal/kg GE). Animals were weighed prior to the experiment to adjust feed supply to approximately 1% of body weight per day. Before and after the reproductive period, 10 females and 10 males per treatment were randomly sampled for blood collection (3 mL) to analyze biochemical parameters (total protein, glucose, triglycerides, cholesterol, urea, uric acid, calcium, and phosphorus). Reproductive data, including nesting, incubation, hatching, and sexing of offspring, were also recorded. Females fed 4,600 kcal/kg exhibited higher body weight (43.14 ± 8.59 kg) compared to those fed 3,900 kcal/kg (33.11 ± 7.55 kg). Eggs from the higher-energy treatment were larger in length (39.83 ± 1.63 mm vs. 37.61 ± 2.00 mm) and heavier (39.18 ± 3.53 g vs. 31.87 ± 4.43 g). Hatchlings from these females were heavier at birth (26.66 ± 1.97 g vs. 21.16 ± 2.78 g) and at six months of age (85.73 ± 20.77 g vs. 56.55 ± 14.45 g). However, the higher-energy diet was associated with lower hatching rates (27.85 ± 32.87% vs. 52.64 ± 33.62%) and a greater number of infertile eggs. These results indicate that maternal dietary energy level significantly influences biometric performance and reproductive investment, promoting enhanced early growth of hatchlings but negatively affecting hatching success. In females, both year and dietary energy level significantly affected most biochemical parameters, with higher concentrations of energy, protein, and mineral metabolites observed in animals fed 3,900 kcal/kg (triglycerides = 99.89 ± 71.93 mg/dL; cholesterol = 95.00 ± 34.71 mg/dL; glucose = 70.07 ± 19.72 mg/dL; calcium = 8.88 ± 2.95 mg/dL; phosphorus = 5.31 ± 2.07 mg/dL), whereas the 4,600 kcal/kg diet resulted in higher urea levels (21.71 ± 7.46 mg/dL). In males, year influenced triglycerides, glucose, calcium, and phosphorus, while dietary energy affected only plasma calcium (8.68 ± 2.69 mg/dL at 3,900 kcal/kg and 7.91 ± 3.13 mg/dL at 4,600 kcal/kg). The interaction between energy and year was significant for total protein and glucose in females and for uric acid in males. Sex had a significant effect on all evaluated parameters except calcium, with females showing higher values for most variables, except urea. Moderate dietary energy levels (3,900 kcal/kg) appear to be associated with improved physiological balance in breeding Amazon river turtles. Overall, dietary energy and protein levels significantly influence reproductive performance, highlighting the importance of proper nutritional management in captive breeding systems and ex situ conservation strategies.