Natali Miwa Kunita

Associação entre características de desempenho de tilápia-do-nilo ao longo do período de cultivo

The objective of this work was to estimate the structure and heritability of genetic correlations between the performance traits of Nile tilapia (Oreochromis niloticus) of the GIFT lineage during different stages of the production cycle. The Nile tilapias were grown in net cages. Daily total weight gain, live weight, and daily weight gain were measured in four periods, in approximately 30-day intervals. One-trait analyses were performed for all biometric measurements, and, in the two-trait analyses, measurements of the same traits were combined in pairs and to daily total weight gain. Estimated heritabilities ranged from 0.15 to 0.11 for live weight, from 0.16 to 0.09 for daily weight gain, and from 0.17 to 0.12 for daily total weight gain in the one-trait analyses. Estimated values of genetic correlation for live weight and daily weight gain, associated with daily total weight gain, ranged from 0.37 to 0.98 and from 0.74 to 0.88, respectively. The high genetic correlation estimated between live weight in intermediate biometric measurements and daily total weight gain suggests that selection for growth rate may be performed earlier.

Resposta à seleção de características de desempenho e morfométricas de tilápia-do-nilo ao longo do período de cultivo

The objective of this work was to study the selection response for performance and morphometrics traits in Nile tilapias (Oreochromis niloticus) in different measurements of farming. The one-trait analysis was performed for all traits studied and the two-traits analysis, were associated with the daily total weight gain in four measurement among performance and morphometrics traits in the fourth measurement. The heritabilities estimated for live weight, height and head length were higher in one-trait analysis than two-traits analysis. The genetic correlations, phenotypic, Pearson and Spearman among weight gain and all other measurements were higher along the farming. The indirect response was estimated at over 87% of direct response, which indicates that the selection may be performed early, using the daily total weight gain as selection criteria in intermediate measurement, without significant losses in genetic gain and contributing to reduction of cost production.

Avaliação genética de características morfométricas em tilápias do Nilo cultivadas

Breeding values, the differences in responses to selection, the (co)variance components and genetic parameters of the morphometrics traits of Nile tilapia (O. niloticus) reared in cages were estimated. Morphometric and performance traits of 1824 animals were analyzed. The estimated heritability ranged from 0,08541 to 0,194 and the proportion of the variation due common environ-mental/hatchery and nursery effects ranged from 0,07402 to 0,1586 and 0,00087 to 0,079, respectively. The values of genetic correlations and ranking indicated a strong association between genetic traits. The largest genetic gains were for weight and daily weight gain, and the best response to indirect selection was checked for weight. Selection for growth rate led to genetic gain in morphometric traits.

Respostas à seleção de características de desempenho em tilápia‑do‑nilo

The objective of this work was to estimate genetic parameters and direct and indirect responses to selection for performance traits in Nile tilapia ( Oreochromis niloticus ), as well as to evaluate the impact of selection on genetic gain. Information about Nile tilapia, under selection in a genetic improvement program, grown in a net‑tank system, from 2008 to 2010, was used. Heritability and genetic correlations for the traits daily weight gain, and, immediately after catching, weight, width, height, and trunk length were estimated, besides the genetic gains obtained by the estimation of genetic tendencies and of the responses to selection for these traits. Heritability estimates were around 30%. The estimates of genetic and rank correlations had high magnitude. The direct genetic gain for daily weight gain was 7.9, 5.18, and 9.43% in 2008, 2009, and 2010, respectively. The genetic gains obtained from the genetic tendencies were 6.36, 6.30, 1.62, 1.65, and 1.51%, respectively, for daily weight gain, and trunk weight, width, height, and length. The increased growth rate through selection positively impacts performance traits in Nile tilapia.

Genetic parameters in female reproductive traits of Nile tilapia (Oreochromis niloticus)

Genetic parameters for reproductive traits in female Nile tilapia were estimated in this study using Bayesian inference method. The data set presented information from 451 Nile tilapia females that were evaluated at two different places in Maringá - Paraná - Brazil (hapas of 1 and 10 m³) and at one location in Alfenas - Minas Gerais - Brazil. A spawning examination was conducted once a week from October 2012 to March 2013 for a total of 23 weeks of evaluation. Single-trait analyses for spawning success, multiple spawning, spawning frequency, and volume of eggs/female were performed by using the software MTGSAM Threshold. The heritability estimates were 0.14, 0.16, 0.53, and 0.08 for spawning success, multiple spawning, spawning frequency and volume of eggs/female, respectively, indicating it is possible to achieve a substantial genetic gain using these reproductive traits as selection criteria.

Avaliação genética de tilápias‑do‑nilo durante cinco anos de seleção

The objective of this work was to estimate genetic parameters and breeding values for body weight at harvest and daily weight gain of Nile tilapia (Oreochromis niloticus), evaluated in cages for five years. The data set contained records of 6,650 animals, with predicted breeding values of 8,590 animals in the relationship matrix. The number of animals evaluated was 2,196 (33 families) in 2008; 1,721 (58 families) in 2009; and 2,733 (78 families) in 2010. Single and two-trait analyses from the data set were performed using Bayesian inference methodology by the computer program MTGSAM. The obtained heritability estimates were of medium magnitude, as follows: 0.273, for daily weight gain; and 0.282, for body weight at harvest. The participation of common environmental effects in the total variation was of 15% for larvae and 5% for nurseries. The genetic and phenotypic correlations were of 95%, indicating a strong association between the traits. Genetic gain was 3.8% per generation, with accumulated 15% over four generations. There were genetic progress and changes caused by the selection of Nile tilapia in the evaluated growing conditions. The selection for weight gain allows of indirect gains associated to weight.