UBC Theses and Dissertations
UBC Theses and Dissertations
Enhancement of the non-specific immune response, pigmentation and growth of farmed Chinook salmon (Oncorhynchus tshawytscha) fed a combination of dietary flavonoids (grape seed extract, KPA®) and astaxanthin Schlicht, Alberto
Salmon farming is a flourishing aquaculture industry throughout the world and relies on intensive husbandry practices and well balanced diets to succeed. As in agriculture, genetics, health, husbandry, and nutrition are the main pillars of a successful and sustainable industry. Astaxanthin, a xanthophyll pigment with antioxidant properties, is incorporated into farmed salmon diets to provide the desirable red colour in flesh. Dietary antioxidant supplements (i.e. vitamins, flavonoids) have been shown to fight free radicals normally formed during aerobic metabolism and generated in excess during some physiological and pathological processes (i.e. exercise, disease). This research was conducted to investigate the role of dietary supplementation, with grape seed extract and astaxanthin, on pigmentation, growth and the immune response, of pre-smolt and post-smolt chinook salmon spp maintained in freshwater (FW) and saltwater (SW). Four experimental diets were formulated that contained uniform amounts of astaxanthin (60 ppm) and one of two concentrations (low and high) of grape seed extract (Kikkoman Proanthocyanidins, KPA®). The control diet (no astaxanthin, no KPA®), astaxanthin diet (astaxanthin, no KPA®), low KPA® diet (astaxanthin, 100 ppm KPA®), and high KPA® diet (astaxanthin, 1000 ppm KPA®) were fed for 32 days to pre-smolt chinook salmon in FW tanks, and 155 days to post-smolt chinook salmon in SW growout seacages. Pre-smolts fed fortified diets with the antioxidants KPA® and astaxanthin, showed a significantly (p=0.043) larger weight gain than fish groups fed the control diet after 32 days. There were no significant weight differences among the groups ingesting the antioxidant-fortified diets. The specific growth rates (SGR) and feed conversion ratios (FCR) were not significantly different between groups fed the four experimental diets in FW. Conversely, muscle astaxanthin concentrations were significantly higher (p=0.019) in groups fed the astaxanthin-containing diets compared to baseline values and fish fed the control diet. There were no significant differences either in the concentration of astaxanthin in fish muscle or on the apparent astaxanthin retention coefficients (AARC) in salmon fed either the astaxanthin, low or high KPA® diets. After a feeding period of 155 days in SW, post-smolts fed the high KPA® diet had a significantly higher deposition of astaxanthin in muscle (p=0.036), higher visual colour score in fillets as measured by the Roche Salmofan® (p=0.029), and greater wet weight gain (p<0.001) than those fed the other three diets. Following a disease challenge with Vibrio anguillarum, pre-smolts fed the high KPA® diet had a significantly lower (p=0.038) cumulative mortality among diet treatments, as well as a significantly greater (p=0.025) number of circulating leucocytes (p=0.025), neutrophils (p=0.018), and monocytes (p=0.034). Furthermore, the lysozyme activity both in plasma and head kidney, and the neutrophil respiratory burst activity were significantly greater in fish fed the high KPA® diet, (p=0.029, p=0.037, and p=0.027, respectively). It is concluded that the addition of antioxidants (proanthocyanidins and astaxanthin) to a chinook salmon diet significantly enhanced the humoral and cellular non-specific immune response factors and was related to a lower cumulative mortality after the disease challenge. Furthermore, the deposition efficiency of the carotenoid astaxanthin, and growth-related variables in farmed chinook salmon were also significantly affected by the combination of dietary antioxidants.
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