Gro Ingunn Hemre

Atlantic Salmon (Salmo salar): The “Super-Chicken” of the Sea?

In this article, the definition of sustainability is discussed, particularly in relation to the use of marine feed resources. The current review gives an overview of the development of Atlantic salmon (Salmo salar) aquaculture and how it has evolved due to changes in legal and management framework conditions. Atlantic salmon production is characterized with high utilization of nutrients, a high yield of production, and a large demand for rendered by-products. All of these factors compare favorably to production of most terrestrial farm animals. Historically, salmon feed has contained fishmeal and fish oil as the primary protein and fat source. Rising demand for feed ingredients has not increased pressure on forage fish resources. Rather, there has been an increased use of plant protein and fat sources. Increased utilization of plant ingredients may not be as sustainable as often claimed. Provided that marine harvest is carried out within legal frames, harvesting the marine ecosystem is a sustainable operation, and at present, the only significant source of long chain n-3 fatty acids. It is concluded that Atlantic salmon farming can be compared to raising a marine “super chicken” being among the most sustainable meat products in the world food market.

Digestibility of dry matter, protein, starch and lipid by cod, Gadus morhua: comparison of sampling methods

Atlantic cod were fed 11 different extruded diets spanned by a multiple simplex design. The dietary ranges of protein, fat and starch were 36-66%, 8-28% and 8-18%, respectively. All diets contained 0.1% yttrium oxide as an inert marker. After several months of feeding, faeces were sampled, either by stripping or by dissecting the last part of the intestine, which in turn was frozen and faecal matter removed while still partly frozen. No significant differences were found in average digestibility results of dry matter, protein, starch or lipid when comparing the two methods of sampling. All groups showed high digestibility of dry matter, protein and lipid, with minor variations, and only extreme feed compositions resulted in changed digestibility of dry matter and protein. A larger variation was found in apparent starch digestibility, from 60% to 90%, however, independent of dietary level when this was below 17% of dry matter, in agreement with findings for this nutrient as concerns other carnivorous fish. No difference was detected for any of the compared digestibility coefficients when evaluating the four centre points of the multiple simplex design. In conclusion, no difference between methods gives the opportunity to freely choose sampling method, and either stripping or dissection of faecal matter can be used to determine apparent digestibility values in cod.