Rtm. Baker, THE EFFECTS OF DIETARY ALPHA-TOCOPHEROL AND OXIDIZED LIPID ON POSTTHAW DRIP FROM CATFISH MUSCLE, Animal feed science and technology, 65(1-4), 1997, pp. 35-43
DL-alpha-tocopheryl acetate was added at different concentrations (20
or 100 mg kg(-1)) to catfish diets containing either fresh or oxidised
(rancid) oil to determine the effects on tissue alpha-tocopherol leve
ls, fatty acid composition and post-thaw exudative moisture loss from
fillets of African catfish (Clarias gariepinus). Following a 56-day fe
eding trial in which duplicate groups of twenty 15.7-g catfish were fe
d diets at a ration level of 3% body weight per day, it was recorded t
hat for any given oil status, muscle alpha-tocopherol responded signif
icantly (P < 0.05) to elevations in dietary DL-alpha-tocopheryl acetat
e. Oil quality exerted a profound effect on muscle alpha-tocopherol le
vels, with fillets from fish fed oxidised diets exhibiting significant
ly (P < 0.05) lower alpha-tocopherol concentrations, despite similar d
ietary tocopherol-ester contents. Decreased PUFA content was recorded
in fillets from fish fed rancid-oil diets, although dietary alpha-toco
pherol was successful in lessening the effect. Post-thaw exudative moi
sture losses from fillets after refrigerated storage for 48 h was sign
ificantly (P < 0.05) greater in treatments fed oxidised- rather than f
resh-oil diets. Within the oxidised treatments, elevated dietary alpha
-tocopheryl acetate inclusion resulted in a lessening of the moisture
loss, thus demonstrating the protective effect of vitamin E against fr
eeze damage of muscle-tissue membranes. After 96 h, the significant di
fferences (P < 0.05) in exudative losses between treatments was solely
due to muscle alpha-tocopherol concentration. Hence, alpha-tocopherol
was shown to be the most important factor in the maintenance of post
mortem membrane stability. In this investigation supplemental dietary
vitamin E afforded some degree of protection to Clarias tissues, again
st the stresses involved with the consumption of rancid feeds. (C) 199
7 Elsevier Science B.V.