The effect of dietary supplementation with zooplankton or fish protein hydrolysate on Atlantic cod (Gadus morhua) production traits and physiology

• Main Author: Katan, Tomer
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2014
• Subjects: atlantic cod; Gadus morhua
• Online Access: https://research.library.mun.ca/6460/; https://research.library.mun.ca/6460/1/Katan_Tomer_052014_MSc.pdf.pdf; https://research.library.mun.ca/6460/3/Katan_Tomer_052014_MSc.pdf.pdf

This thesis examined the effects of partial dietary supplementation with wild- zooplankton or fish protein hydrolysate on cod production traits, and how they related to the cod’s physiology and the expression of growth and appetite regulating genes. Atlantic cod larvae were fed three different diets: enriched rotifers / Artemia (RA); RA + fish protein hydrolysate (RA-PH); and RA supplemented with 5-10% wild zooplankton (RA-Zoo). Partial supplementation with zooplankton significantly improved the dry weight at 60 dph (by approximately 4-fold), specific growth rate (by 2.5% day-1) and the general development of cod larvae. In contrast, the protein hydrolysate enrichment did not improve growth, had a negative effect on survival, and increased the incidence of external deformities in 18 month post-hatch juveniles. Although the zooplankton fed cod were still larger at approximately 1.5 years of age, the growth advantage of this group decreased with age (the difference in wet mass decreasing from approx. 30% at 0.5 years old to 11% at 1.5 years old). Metabolic parameters, and pre- and post-stress cortisol levels, were similar in juvenile cod from the RA and RA-Zoo groups. Finally, the growth enhancement observed in the zooplankton fed larvae was not related to alterations in the mRNA expression of the main growth regulating genes [Insulin-Like Growth Factor 1 (IGF-1); IGF-2; Growth Hormone (GH); GH Receptor-1 (GHR-1); GHR-2; and myostatin] or appetite regulating hormones [(Cocaine and Amphetamine Regulated Transcript (CART) and Neuropeptide Y (NPY)]. This latter finding suggests that the transcript levels of these hormones and hormone receptors are not a valuable biomarker for growth in cod larvae.