RESUMO

Variance components and heritabilities for daily weight gain (DWG) were estimated for Nile tilapia farmed in cages across nine generations (G1-G9) of selection in a breeding program in Brazil. DWG was measured in 16,272 accumulated tagged animals representing 535 full- and half-sib families of Nile tilapia under cage farming. The additive genetic variance showed a slight variation (0.051-0.066), and heritability estimates ranged from 0.20 to 0.33. The common environmental effect accounted for a higher proportion of the total variance in DWG, especially in the last generations (6%-24%). A genetic trend based on all data available showed a substantial increase in the DWG (about 3.3% per generation) of Nile tilapia across nine generations of selection. Furthermore, our results demonstrate ample scope for further genetic improvement.

Assuntos

RESUMO

Nile tilapia (Oreochromis niloticus) is the major fish species produced in Brazil, a country with a vast territory and great climate diversity. This study assessed the effects of the genotype × environment interaction on heritability estimates and selection responses in Nile tilapia (Tilamax strain) cultivated in earthen ponds and net cages. The weight at harvest, trunk length, and head percentage of 4400 individuals were determined. Trait heritabilities were higher in pond fish (0.27-0.52) than in caged fish (0.09-0.33). Genetic correlations between farming systems were lower than 0.5 for the three traits. The rank position of the top 10 families differed according to the environment, as did the response to direct and indirect selection. The results revealed significant genotype × environment effects on the heritability of Nile tilapia farmed under different systems.

Assuntos

RESUMO

Improvement of fillet traits and flesh quality attributes are of great interest in farmed tilapia and other aquaculture species. The main objective of this study was to estimate genetic parameters for fillet traits (fillet weight and fillet yield) and the fat content of fillets from 1136 males combined with 2585 data records on growth traits (body weight at 290 days, weight at slaughter, and daily weight gain) of 1485 males and 1100 females from a third generation of the Aquaamerica tilapia strain. Different models were tested for each trait, and the best models were used to estimate genetic parameters for the fat content, fillet, and growth traits. Genetic and phenotypic correlations were estimated using two-trait animal models. The heritability estimates were moderate for the fat content of fillets and fillet yield (0.2-0.32) and slightly higher for body weight at slaughter (0.41). The genetic correlation between fillet yield and fat was significant (0.6), but the genetic correlations were not significant between body weight and fillet yield, body weight and fat content, daily weight gain and fillet yield, and daily weight gain and fat content (- 0.032, - 0.1, - 0.09, and - 0.4, respectively). Based on the genetic correlation estimates, it is unlikely that changes in fillet yield and fat content will occur when using growth performance as a selection criterion, but indirect changes may be expected in fat content if selecting for higher fillet yield.

Assuntos

RESUMO

The goals of this study were to evaluate the effects of a mannan-oligosaccharide (MOS) and a frutoligosaccharide (FOS) mixture in a 1:1 ratio added to a commercial diet for dogs before the extrusion process on the coefficient of total tract apparent digestibility (CTTAD) of the diets and on the metabolizable energy (ME), nitrogen metabolism (postprandial blood urea curve, organic nitrogen balance, fecal concentration of ammonia and excretion of urinary urea) and fecal fermentation parameters (fecal pH and concentrations of short chain fatty acids). Eighteen adult Beagle dogs were used and randomly distributed into two treatments, being a control diet plus one diet in which the mixture of prebiotics was added before the extrusion of the ration. There was no difference in digestibility, metabolizable energy, fecal ammonia content and short-chain fatty acids (acetic, propionic and butyric) between the control diet and the one with the addition of prebiotics. However, the dogs supplemented with prebiotics before extrusion, had a lower fecal pH (p 0,05) compared to those in the control diet and a reduction in the post prandial blood urea concentration (p 0,01) was also observed in the animals receiving prebiotics, observed by the areas below the curve of urea and its increment. The possible mechanism involved in the effect of prebiotics on the reduction in the concentrations of blood urea is thereduction in the formation and intestinal absorption of ammonia, favored by the reduction of intestinal pH. These findings can be considered in the use of prebiotics in clinical nutrition.(AU)

Neste trabalho, objetivou-se avaliar os efeitos de uma mistura de mannan-oligossacarídeos (MOS) e frutoligossacarídeos (FOS), na proporção de 1:1 adicionados a uma dieta para cães, antes ou após o processo de extrusão, sobre os coeficientes de digestibilidade aparente das dietas, energia metabolizável, metabolismo do nitrogênio (curva de uréia sérica pós-prandial, balanço orgânico de nitrogênio, concentração fecal de amônia e excreção de uréia urinária) e parâmetros fermentativos fecais (pH fecal e concentrações de ácidos graxos de cadeia curta). Foram utilizados 18 cães adultos da raça Beagle, distribuídos ao acaso em três tratamentos, sendo uma ração controle mais duas dietas em que a mistura dos prebióticos foram adicionados antes ou após o processo de extrusão das rações. Não houve diferença na digestibilidade, energia metabolizável, teor de amônia fecal e de ácidos graxos de cadeia curta (acético, propiônico e butírico) entre as dietas controle e com adição dos prebióticos. Entretanto, os cães suplementados com prebiótico, antes ou após a extrusão, apresentaram menor pH fecal (p 0,05) em relação à dieta controle e foi observado ainda redução na concentração pós-prandial de uréia sérica (p 0,01) nos animais que receberam prebióticos, observados pelas áreas abaixo da curva de uréia e do seu incremento. O processo de extrusão não afetou os efeitos biológicos destes prebióticos sobre os parâmetros avaliados nos cães. Possíveis mecanismos implicados no efeito dos prebióticos sobre a redução nas concentrações de uréia sérica são a diminuição na formação e absorção intestinal de amônia, favorecidas pela redução no pH intestinal. Estes achados podem ser considerados no uso de prebióticos em nutrição clínica.(AU)

Assuntos

RESUMO

The goals of this study were to evaluate the effects of a mannan-oligosaccharide (MOS) and a frutoligosaccharide (FOS) mixture in a 1:1 ratio added to a commercial diet for dogs before the extrusion process on the coefficient of total tract apparent digestibility (CTTAD) of the diets and on the metabolizable energy (ME), nitrogen metabolism (postprandial blood urea curve, organic nitrogen balance, fecal concentration of ammonia and excretion of urinary urea) and fecal fermentation parameters (fecal pH and concentrations of short chain fatty acids). Eighteen adult Beagle dogs were used and randomly distributed into two treatments, being a control diet plus one diet in which the mixture of prebiotics was added before the extrusion of the ration. There was no difference in digestibility, metabolizable energy, fecal ammonia content and short-chain fatty acids (acetic, propionic and butyric) between the control diet and the one with the addition of prebiotics. However, the dogs supplemented with prebiotics before extrusion, had a lower fecal pH (p 0,05) compared to those in the control diet and a reduction in the post prandial blood urea concentration (p 0,01) was also observed in the animals receiving prebiotics, observed by the areas below the curve of urea and its increment. The possible mechanism involved in the effect of prebiotics on the reduction in the concentrations of blood urea is thereduction in the formation and intestinal absorption of ammonia, favored by the reduction of intestinal pH. These findings can be considered in the use of prebiotics in clinical nutrition.

Neste trabalho, objetivou-se avaliar os efeitos de uma mistura de mannan-oligossacarídeos (MOS) e frutoligossacarídeos (FOS), na proporção de 1:1 adicionados a uma dieta para cães, antes ou após o processo de extrusão, sobre os coeficientes de digestibilidade aparente das dietas, energia metabolizável, metabolismo do nitrogênio (curva de uréia sérica pós-prandial, balanço orgânico de nitrogênio, concentração fecal de amônia e excreção de uréia urinária) e parâmetros fermentativos fecais (pH fecal e concentrações de ácidos graxos de cadeia curta). Foram utilizados 18 cães adultos da raça Beagle, distribuídos ao acaso em três tratamentos, sendo uma ração controle mais duas dietas em que a mistura dos prebióticos foram adicionados antes ou após o processo de extrusão das rações. Não houve diferença na digestibilidade, energia metabolizável, teor de amônia fecal e de ácidos graxos de cadeia curta (acético, propiônico e butírico) entre as dietas controle e com adição dos prebióticos. Entretanto, os cães suplementados com prebiótico, antes ou após a extrusão, apresentaram menor pH fecal (p 0,05) em relação à dieta controle e foi observado ainda redução na concentração pós-prandial de uréia sérica (p 0,01) nos animais que receberam prebióticos, observados pelas áreas abaixo da curva de uréia e do seu incremento. O processo de extrusão não afetou os efeitos biológicos destes prebióticos sobre os parâmetros avaliados nos cães. Possíveis mecanismos implicados no efeito dos prebióticos sobre a redução nas concentrações de uréia sérica são a diminuição na formação e absorção intestinal de amônia, favorecidas pela redução no pH intestinal. Estes achados podem ser considerados no uso de prebióticos em nutrição clínica.

Assuntos