EFFECTS OF DIETARY VEGETABLE, ANIMAL AND MARINE LIPIDS ON MUSCLE LIPID AND HEMATOLOGY OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

The effects of dietary vegetable and animal fats on the growth, nutrition, and tissue lipid profiles of rainbow trout raised to market size on a commercially available diet were examined. Rainbow trout of 80 g mean initial weight were fed pellets prepared according to Oregon Moist Pellet (OMP) specifications for 20 weeks. Salmon oil (OMP-1), soybean oil (OMP-2), linseed oil (OMP-3), chicken fat (OMP-4), pork lard (OMP-5) and beef tallow (OMP-6) were used for the lipid component of the diets. No differences in feed conversion or growth rate were observed across diet groups. Hematological tests revealed oxidative stress caused by the OMP-1 diet, as measured by hemolysis, while hematocrit and percent hemoglobin values fell within a narrow range across diet groups. Only 10-12% of lipid in trout on diets OMP-2-6 was deposited as 20:5n-3 plus 22:6n-3 despite the availability of dietary precursor (18:3n-3) to further elongate and desaturate to 20:5n-3 and/or 22:6n-3. Dietary ratios of 20: 1 20:1, ranging from 0.6 to 0.8, also were modified to 0.5 in the muscle tissue of trout on all diets. This consistent pattern suggests that a physiologically optimum level of long chain fatty acids is maintained in rainbow trout. © 1990.