Use of ultrasonography to collect phenotypes and estimate genetic parameters of carcass characteristics in tilapia (Oreochromis niloticus)

Abstract

The growth of fish farming in Brazil and worldwide over the last decade has been evidenced by the significant increase in production and meat quality. In addition, the development of technological packages at various stages of the production cycle has contributed to boosting this productive sector. Genetic improvement is part of this set of technologies that has led to significant gains in aquaculture productivity. Among the various approaches used to select superior phenotypes, ultrasound has proved to be an important ally in this process. The use of ultrasound to collect phenotypes began in the early 2000s and has proven to be effective, but the lack of standardization of this technique can result in inaccuracies, which prevents the common incorporation of this tool into genetic improvement programs. In this context, this study aimed to standardize the collection of phenotypes by ultrasound in order to estimate genetic parameters related to carcasses. The study was divided into two stages. The first stage was carried out on 30 randomly selected animals, from which ultrasound images of the fifth, eleventh and posterior dorsal fin were collected. The device used was the VinnoQ 7 series, with the probe operating at 10 MHz and a wave depth of 3.5 cm. After the images were taken, the animals were slaughtered by medullary section and the fillets removed, weighed and divided into fillet and belly. The high phenotypic correlations obtained (0.78 - 0.99) showed that ultrasound is highly accurate and that the areas of meat measured in the images have a high coefficient of determination (R2) in the models for estimating fillet yield. The second stage of the study was carried out at the Federal University of Lavras and included 897 animals from 43 families. The collection of ultrasound images followed a previously defined pattern, using the same device and the exact locations on the fish's bodies. The meat areas of the three body points and the yields were evaluated in silico using the MTGSAM program to obtain the genetic parameters for each trait and the genetic correlations with fillet yield. The estimated heritabilities were moderate (0.25 - 0.33), and the genetic correlations between the areas obtained by ultrasound and fillet yield were high (0.83 - 0.92). The results allow us to conclude that the collection of carcass characteristics using ultrasound is efficient and can be used to obtain genetic gains correlated with fillet yield.