Effects of dietary fish oil and corn oil on gonadosomatic and hepatosomatic index, gonadal histology, 17β-oestradiol level and fatty acids profile of mahseer (Tor tambroides) broodstock in captivity

<p>The present research was conducted to investigate the effects of fish oil (FO) substitutions with corn oil (CO) on the gonad development of female <i>Tor</i> <i>tambroides</i> broodstocks, a high value freshwater fish. Three isonitrogenous (450 g kg⁻¹ crude protein) and isolipidic (105 g kg⁻¹ crude lipid) were formulated to contain FO and CO at a ratio of 1:0, 1:1 and 0:1, respectively, and fed to female fish (<i>n</i> = 10 fish × 3 replicate × 3 treatment; average weight = 910.0 ± 130.0 g) for five months. At the end of the feeding trial, there were no significant differences (<i>p</i> > .05) on the gonadosomatic index (GSI), hepatosomatic index, 17β-oestradiol (E2) concentration and muscle fatty acids (FA) composition. However, fish fed with diet containing FO to CO at a ratio of 1:1 demonstrated higher percentage of GSI, E2 concentration (ng ml⁻¹) and the presence of vitellogenic oocytes in the histological data compared to the other two feeding diets. The FA composition also highlighted that <i>T</i>. <i>tambroides</i> broodstocks can elongate polyunsaturated FA to highly unsaturated FA. Based on these preliminary results, it shows that <i>T</i>. <i>tambroides</i> prefer diets with supplementation of both n3 and n6 oil source. However, more studies need to be done to strengthen this conclusion.</p>