Submitted to: International Aquatic Animal Health Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2014
Publication Date: 9/1/2014
Citation: Lapatra, S.E., Leeds, T.D., Wiens, G.D. 2014. From the laboratory to the field: The performance of a selectively bred line of Rainbow Trout (Oncorhynchus mykiss) under commercial production conditions [abstract]. International Aquatic Animal Health Symposium Proceedings. Paper No. 302.
Technical Abstract: Selective fish breeding programs for disease resistance comprise an increasingly important role in aquaculture production and offer an additional management tool for reducing bacterial-caused disease losses. Bacterial cold water disease (BCWD) is one of the most frequent causes of elevated mortality in juvenile salmonids, and a genetic line of rainbow trout has been selectively bred by the USDA-ARS for resistance to BCWD. This line is designated ARS-Fp-R (resistant) and has been shown to be significantly less susceptible than randomly-mated control and industry reference lines following standardized laboratory challenges with the causative agent of BCWD, Flavobacterium psychrophilum. Further, there has been no clinical diagnosis of BCWD in the ARS-Fp-R line in five completed field trials to date where exposure to the pathogen was confirmed and BCWD was diagnosed in contemporary fish. However, this line was shown to potentially have increased susceptibility to infectious hematopoietic necrosis (IHN) virus in one laboratory evaluation. In 2013, a production lot farm trial utilizing 300,000 eyed-eggs obtained from the ARS-Fp-R line was initiated at Clear Springs Foods (CSF), Inc. and survival was monitored from hatching through harvest. Survival during hatch-house rearing was high and fish were vaccinated against ERM and IHN virus utilizing standard CSF protocols. Feeding and mortality were normal until day 189 post-hatch. At this point, elevated mortality occurred and systemic or hematopoietic IHN was diagnosed concomitantly with a minor gill flavobacterial infection. Fish were treated with chloramine-T three times during one week. Subsequently, over the course of 25 days an estimated 19% of the fish were lost to IHNV (n=14,284) before mortality returned to baseline. No additional mortality events were recorded following this outbreak through harvest (~385 days post-hatch). Feed conversion rate and fillet yield were judged to be favorable and within typical production limits. Based on results from this farm trial and historical experience with IHN virus mortality at CSF, the ARS-Fp-R line appears to potentially have increased IHNV susceptibility compared to other commercial rainbow trout lines. Additional production trials are planned or in progress with this and other selected USDA-ARS lines of rainbow trout.