Marcelo Maia Pereira

Non-linear growth models for bullfrog tadpoles

Describing animal growth rate using non-linear models allows a detailed evaluation of growth behavior. Four non-linear models were used to fit weight gain and total length data of bullfrog (Lithobates catesbeianus) tadpoles, as follows: Gompertz, Y = A exp (-exp (-b (t-T))); Von Bertalanffy, Y = A (1 - K exp (-B t))3; Logistic, Y = A (1+ K exp (-B t))-1 and Brody, Y=A (1 - K exp (-B t)). We used 3,240 tadpoles, with average initial weight 0.044 g and average total length 12.79 mm, stage 25 Gosner. The measurements were conducted every ten days on 10% of the animals in every tank. The criteria used to select the model that best described the growth curve were: Residual Mean Square (RMS); determination coefficient (R2); residual graphical analysis; residual mean absolute deviation (MAD). Brody mathematical model was not a good fit for weight gain and total length, while Von Bertalanffy model underestimated tadpole initial weight, thus showing the difficulty of mathematical models to describe biological data at this growth stage. However, the Gompertz and Logistic models were considered to be an adequate fitting to describe growth rate and total length of bullfrog tadpoles in captivity.

Growth in weight and of some tissues in the bullfrog: fitting nonlinear models during the fattening phase

Knowledge of the growth of animals is important so that zootechnical activity can be more accurate and sustainable. The objective of this study was to describe the live weight, development of liver tissue and fat body, leg growth, and cumulative food intake of bullfrogs during the fattening phase using nonlinear models. A total of 2,375 bullfrog froglets with an initial weight of 7.03 ± 0.16 g were housed in five fattening pens (12 m2). Ten samplings were performed at intervals of 14 days to obtain the variables studied. These data were used to estimate the parameters of Gompertz and logistic models as a function of time. The estimated values of weight (Wm) and food intake (FIm) at maturity and time when the growth rate is maximum (t*) were closer to expected values when the logistic model was used. The Wm values for live weight and liver, adipose and leg weights and the FIm value for food intake were 343.7, 15.7, 19.6, 96.03 and 369.3 g, respectively, with t* at 109, 98, 105, 109 and 107 days. Therefore, the logistic model was the best model to estimate the growth and food intake of bullfrogs during the fattening phase.

Desempenho zootécnico de girinos de rã-touro com diferentes níveis de proteína e energia digestíveis

From the digestibility values of some ingredients, it was proposed diets with different levels of digestible protein and energy, in a 3x3 factorial design for bullfrog tadpoles, aiming at evaluate the zootechnical performance. The experiment was conducted during 60 days with 810 tadpoles from the same spawning distributed into 27 polypropylene boxes at a density of 1 tadpole/L. The experimental design consisted of a factorial arrangement with three levels of digestible protein (27; 31 and 35%) and three levels of digestible energy (2700; 2800 and 2900kcal/kg) with three repetitions. Parameters evaluated at 60 days were weight gain, feed intake, dietary protein intake, feed conversion, protein efficiency rate and survival rate. Results were subjected to analysis of variance and Duncan test (95% accuracy), and presented no interaction between digestible protein and digestible energy for any parameter evaluated. As for the digestible protein, significant differences were detected in the dietary protein intake, and protein efficiency rate, evidencing inefficiency of diets with high protein values. Bullfrog tadpoles should be given diets with 27% digestible protein by having the best result for the protein efficiency rate and for the dietary protein intake, with the lowest value and similar to other levels among evaluated parameters.

Deposição de nutrientes na carcaça de girinos de rã-touro

O objetivo deste trabalho foi determinar a deposicao de nutrientes na carcaca de girinos de ra-touro (Lithobates catesbeianus) por meio de modelo nao linear. Foram utilizados 2.700 girinos com peso medio inicial de 0,039 g. Racao comercial farelada com 55% de proteina bruta foi fornecida ad libitum. Os animais foram pesados e avaliados a cada dez dias para analise dos conteudos de proteina bruta, extrato etereo, agua e sais minerais. Os parâmetros do modelo Gompertz foram estimados pelo metodo de Gauss-Newton modificado, e as taxas de deposicao (g por dia) em funcao do tempo foram calculadas por meio da derivada da equacao. Os valores encontrados para os parâmetros da equacao de Gompertz, para descrever a deposicao dos nutrientes na carcaca de girinos, apresentaram interpretacao biologica. A taxa maxima (t*) de deposicao foi observada aos 36,2331 dias para proteina, aos 37,1420 dias para agua, aos 35,2971 dias para sais minerais, e aos 41,3547 dias para gordura. O consumo de nutrientes da dieta e maior do que a taxa de deposicao na carcaca dos girinos.

Nonlinear models for morphometric analysis in Bullfrog Tadpoles

As relacoes biometricas sao importantes para ilustrar o processo de crescimento dos animais. Estas, quando ajustadas a modelos nao-lineares, podem revelar informacoes importantes para a melhoria das tecnicas de criacao. O conjunto de dados morfometricos em funcao do peso, de quatro experimentos com girinos de ra-touro, foram ajustados aos modelos nao-lineares de Gompertz, Logistico, Von Bertalanffy e Brody, com objetivo de verificar o melhor ajuste. Apos a adequacao dos parâmetros para os diferentes modelos em cada experimento seguiu-se com a comparacao dos mesmos, por meio dos intervalos de confianca (α = 0,05). Os criterios para selecionar os modelos foram: interpretacao biologica, quadrado medio do residuo, coeficiente de determinacao, analise grafica e o numero de iteracoes. Os dados de comprimentos padrao e total em funcao do peso dos girinos convergiram nos quatro modelos. Os modelos Logistico e Gompertz nao apresentaram interpretacao biologica para alguns conjuntos de dados. O quadrado medio do residuo e numero de iteracoes em todos os experimentos e variaveis estudadas apresentaram os menores valores para o modelo de Brody. Os valores de K dos modelos de Brody para comprimento total, quando comparados ao padrao, apresentaram-se menores, indicando que os animais apresentaram um crescimento inicial maior em comprimento padrao. O modelo de Brody foi o mais indicado para descrever o comprimento padrao e total em funcao do peso para girinos de ra-touro.

Diferentes níveis protéicos na dieta de girinos de rã-touro (Lithobates catesbeianus) e seus efeitos sobre o tecido hepático

To verify the occurrence of liver morphological changes, bullfrog tadpoles were fed three diets: an experimental diet with 32.68% crude protein and two commercial diets with 37.92% and 57.53% crude protein. Tadpoles were distributed into a completely randomized design (CRD) with three treatments and four replications. Liver samples were collected twice, on the 30th and 60th day of the experiment. Tadpole livers were fixed in Bouins solution, then subjected to routine histotechnology procedures, and stained with hematoxylin - eosin (HE). Microscopic evaluation of liver tissue showed several morphological changes like disorganization and vacuolization of hepatocytes; periportal, multifocal and diffuse mononuclear inflammatory infiltrate, eosinophilic inflammatory infiltration, congestion, hemorrhage, hemolysis and necrosis. The liver changes found in this study suggest that diets used for bullfrog tadpoles, did not meet their dietary needs, what affected their homeostasis, thus compromising their health.

Qualidade de luz no desempenho da rã-touro na fase de terminação

Os fatores abioticos temperatura, umidade e fotoperiodo influenciam o desenvolvimento e o metabolismo dos anfibios, a partir disto objetivou-se verificar a influencia das luzes vermelha, azul e verde no desempenho da ra-touro na fase de terminacao. Foram utilizadas 480 ras-touro divididas em tres tratamentos e quatro repeticoes. Os parâmetros avaliados foram peso vivo do animal, do corpo adiposo, da carcaca e da pele, ganho de peso por dia, o indice lipossomatico e os rendimentos de carcaca e pele. Os resultados encontrados para os parâmetros avaliados nao diferenciaram (p>0,05) para as diferentes cores de luz. As luzes de cor vermelha, azul e verde nao influenciaram o desempenho da ra-touro na fase de terminacao, mais estudos devem ser realizados sobre outros aspectos relacionados a criacao desta especie.