Before a breeding goal for a breeding programme is determined, scientists document to what extent the variation of each characteristic can be attributed to genes and to the environment. Genetic variation in a characteristic is a prerequisite for improving performance through breeding. The breeding goal also accounts for how important each characteristic is to the industry (this is normally expressed in economic terms).
Breeding goals can vary between species, e.g. red fillet colour is an extremely important characteristic in salmon, while late sexual maturation is an important breeding goal in cod. There are a variety of direct and indirect methods that can be used or hold potential for assessing an animal's performance with relation to the different characteristics in a breeding goal. The following are examples of some of the characteristics that have been included in the breeding goals of programs with which we work, and some of the methods we are developing to measure these characteristics:
Growth
Growth is one of the most important economic characteristics in aquaculture. A fish that grows rapidly will produce more in a shorter time. In breeding, this characteristic is registered as weight at the normal time of slaughter. Salmon provide one example that breeding works: After five generations of breeding for growth, the salmon halved the time required to reach slaughter weight and in doing so the efficiency with which the salmon utilised energy and protein in the feed increased by 25 percent. The opportunity remains for further improvements.
Health
The possibility of outbreaks of contagious diseases at fish farms makes aquaculture a risky business. Heritable variation in resistance to different diseases has been proven in several species. The animals with the best resistance characteristics can be identified by testing the relatives of potential broodstock (in terms of their performance when infected with the disease). But new methods are on the way. Research at Nofima has shown that with the virus disease infectious pancreatic necrosis (IPN), a single gene is 70 percent responsible for the resistance characteristic that lies in the salmon's genes. This is a surprising finding since we believe that disease characteristics are normally controlled by a large number of genes. The gene technology behind this knowledge can now be utilised in breeding programmes. Such knowledge is useful because it tells us something about the risk the animal has of being infected, and by selecting animals with this technology, it reduces the need to screen or infect a large number of animals with the disease.
Nofima's scientists have found a genetic connection between high growth rates in cod and spinal deformities, which means that unbalanced selection of the fish's good growth abilities can lead to an increased problem with deformities in the future. Consequently, it is important that selection decisions for the cod breeding program are made with both rapid growth and low levels of deformity in mind.
Product quality
Genes can explain part of the variation in quality characteristics, and consequently it is relevant to improve these characteristics through breeding. Product quality considerations may include breeding fish for higher fillet yields or a redder muscle colour (salmon). It is advantageous when the characteristics can be measured on the animal itself without it needing to be slaughtered. New technology (near infrared spectroscopy (NIR) developed at Nofima makes this possible.
Research implemented at Nofima shows that we can control the quality characteristics such as slaughter yield and solidity of cod through breeding.
Further description
