We will present some results of an ongoing project aimed at
analysing the major biotic and abiotic factors that influence the
rainbow trout (O. mykiss) productive yield in the Trentino region
(Northern Italy). Five trout strains were compared for their overall
farming performance and suitability to be reared in the local
farms. Eyed-egg samples of different strains were obtained from
local and foreign suppliers. In the first part of the trial, the
strains were compared in terms of egg size, hatching and growth
rates up to the parr stage in a single farm and the intraspecific
genetic variability was assessed using a microsatellites technique
by analysing DNA extracted from random samples of caudal
fin tissue. Significant among-strains differences in growth
performance were found after 8 rearing months. In the second
phase of the trial, parrs of each strain were divided into 4 lots.
Then the lots of the 5 strains were transferred to 4 selected
Trentino trout farms to carry out a performance test up to a market
size of around 0.7 kg. Regardless of the location, all fish lots
were kept at the same density and were fed the same commercial
trout feed, six days a week. Individual weight and length were
measured on random samples of 100 fish per lot every 2 months.
At the same time, major water parameters were registered in the
different farms. Specific growth rate (SGR), thermal growth rate
(TGR), condition factor and feed conversion ratio (FCR) were
calculated. Statistical analyses were performed with SAS and
STATISTICA 9.0. The growth graphs fit quadratic equations and
average daily gain ranged from 1.46 to 1.77 g. Among-strains differences
in growth performance, condition factor, feed conversion
and age at sexual maturity were found at market size.
