February 15-18, 2009 Washington State Convention Center Seattle ...

GROWTH PERFORMANCE OF ATLANTIC COD Gadus morhua LARVAE FED SQUID
HYDROLYSATE PREPARED AT DIFFERENT HYDROLYSIS TIMES
Chong M. Lee*, Qing Pan, Cetin Cetiner and David A. Bengtson
Dept. of Nutrition and Food Sciences
University of Rhode Island
Kingston, RI 02881 USA
chonglee@mail.uri.edu
Squid (Loligo pealei) is currently the most abundant and highest revenue-generating resource in Rhode Island. Squid processing
plants in the region generate about 4,500 metric tons of processing byproduct waste annually. The squid byproduct (Loligo
pealei), composed of heads, viscera, skin, fins, and small tubes, was converted into concentrated hydrolysate (22% solids,
17.3% protein and 3.0 % lipid, primarily phospholipids - 11.6% EPA/ 24.5% DHA on a lipid weight basis). It was hypothesized
that growth and survival of larvae could be affected by feeding larval diet with hydrolysate prepared by different degrees of hydrolysis,
and the degree of hydrolysis should be gradually lessened with the phase of larval growth as larvae develop a gut and
are able to digest more complex proteins. Squid hydrolysates (SH) of two different degrees of hydrolysis were thus prepared at
1 and 2 h at 55°C and incorporated into microparticulate diets as a sole protein source (73% of the whole diet; 56.4% protein,
24.7% lipid, 7.3% carbohydrate and 19.97 MJ/kg, on a dry weight basis). Microdiets were prepared using drum and plate drying
and micronized to 300 µm and 500 µm.
Atlantic cod (Gadus morhua) larvae of 30 d.a.h. previously fed rotifer and Artemia were brought into aquaria at 10°C (20 fish
each in triplicate) and acclimated for 2 wk with DHA-enriched Artemia. Thereafter, larvae were on 3 different microdiets for 6
wk including Artemia for initial 3 wk as a control. Based on the initial 3 wk feeding trial, the growth performance on microdiets
was comparable to that on the Artemia control. After 3 wk feeding period, Artemia was not able to support the normal growth
as larvae passed the weaning phase. The growth performance was assessed in terms of body weight (BW), body length (BL),
body condition factor (BCF) and specific growth rate (SGR). For 6 wk feeding, 63-68% of larvae survived through the weaning
period. Results of growth performance are shown in the table below. No significant differences (p>0.05) in all parameters
studied for growth performance among microdiets prepared with SH of different degrees of hydrolysate (1 h, 2 h hydrolysis
and 2h hydrolysis diet followed by 1h hydrolysis diet). This suggests that 1h hydrolysis was sufficient for SH to be digestible
to larvae and no added benefits are expected from extended hydrolysis. In addition, a two-stage feeding regimen with 2 h SH
diet (more hydrolyzed and lower m.w. peptides) followed by 1 h SH diet (less hydrolyzed and higher m.w. peptides) did not
demonstrate expected benefits as hypothesized.
Growth performance of cod larvae during a 6 wk-feeding on squid hydrolysate microdiets
Diets IBL cm IBW g IBCF FBW (g) FBL (cm) FBCF Survival
SH2 1.76±0.14 0.04±0.01 0.72±0.07 0.505±0.04 4.01±0.08 0.77±0.02 67.7±27 5.99±0.10
SH2-1 1.76±0.14 0.04±0.01 0.72±0.07 0.474±0.01 3.88±0.03 0.79±0.01 65.0±8.7 5.85±0.03
SH1 1.76±0.14 0.04±0.01 0.72±0.07 0.517±0.06 4.04±0.12 0.78±0.04 62.9±12 6.19±0.33
SH1: 1 h hydrolysate microdiet for 6 wk feeding; SH2: 2 h hydrolysate; SH2-1: 2h hydrolysate for 3wk followed by
1 h hydrolysate for 3 wk; IBW (FBW): initial (final) body weight; IBL(FBL): initial (final) body length; IBCF
(FBCF): initial (final) body condition factor; SGR: specific growth rate
(%)
SGR
1