SUPPLEMENTING RAINBOW TROUT BROODSTOCK DIETS WITH CHOLINE AND METHIONINE IMPROVES OFFSPRING GROWTH

Four treatment diets were produced by top-dressing a commercially available finfish broodstock diet (38% protein, 10% fat) with 1) choline (final 7400 ppm), 2) DL-methionine (final 12000 ppm) or 3) choline + DL-methionine.  The fourth diet was the base-diet top dressed by the nutrient vehicle (distilled water) and served as the control.  Six families of female rainbow trout were fed treatment diets at or just below satiation beginning 18 months post-hatch through spawning (n=3 tanks per diet).  Eggs were collected and fertilized using milt from a single family of unrelated males.  Offspring families were reared individually until they were PIT-tagged at approximately 10 g and comingled in three triplicate tanks.  Offspring consumed a single commercially available diet (42% protein, 16% fat) for the majority of the grow-out period.  Lengths and weights were recorded every 2 months.  

There were no differences in maternal body weight, body condition, egg size, or egg yield at spawning that were attributed to broodstock dietary treatments.  There was an effect of broodstock diet on offspring growth performance that was age-dependent (Table 1). Offspring fry from choline-treated broodstock (diet #1) were smaller than fry from other treatment groups through 146 days post hatch (dph, ~11g).  However, by 259 dph, offspring from broodstock that received choline (diets #1 and #3) exhibited greater body weights than offspring from broodstock that received the control feed (diet #4).  By 377 dph body weights of offspring from methionine-treated broodstock (diet #2) also exceeded controls.  Offspring condition factor did not exhibit a consistent response to broodstock diet.  These findings provide strong evidence that dietary intervention strategies in broodstock can affect performance of the offspring.