NUTRITION AND FEEDING 209 



Hatchery operators also started feeding vegetable feedstuffs separately or 

 combined with meat products to provide greater quantities of finished feed. 

 One of the major problems was how to bind the mixtures so they would 

 hold together when placed in the water. In the early days of fish culture, a 

 large portion of artificial feed was leached into the water and lost. This 

 resulted in poor growth, increased mortality, water pollution, and increased 

 labor in cleaning ponds and raceways. The use of dry meals in the diet to 

 reduce feed costs compounded the problem of binding feeds to prevent 

 loss. The use of certain meat products such as spleen and liver mixed with 

 salt resulted in rubber-like mixtures, called meat-meal feeds, that were 

 suitable for trough and pond feeding. These were mixed in a cement or 

 bread mixer and extruded through a meat grinder. This type of feed pro- 

 duced more efficient food utilization, better growth, and a reduction in the 

 loss of feeds. 



However, considerable labor was involved in the preparation of the 

 meat-meal feeds. In addition, the use of fresh meat in the diet required ei- 

 ther frequent shipments or cold storage. The ideal hatchery feed was one 

 that would combine the advantages of the meat-meal feed, but would elim- 

 inate the labor involved in preparation and reduce the expense of cold 

 storage facilities. 



In 1959, the Oregon State Game and Fish Commission began to use a 

 pelleted meat-meal fish feed called Oregon moist pellet (OMP), now com- 

 mercially manufactured. .These pellets were developed because salmon 

 would not take dry feed. Use of this feed in production was preceded by 

 six years of research. The formula is composed of wet fish products and 

 dry ingredients; it has a moist, soft consistency and must be stored frozen 

 until shortly before feeding. 



Many hatcheries use the Oregon moist pellet as a standard production 

 feed because it provides satisfactory feed conversion, and good growth and 

 survival, at a competitive price. The disadvantage of the Oregon moist pel- 

 let is that it must be transported, stored, and handled while frozen. When 

 thawed, it deteriorates within 12 hours. 



By the mid 1950's, development and refinement of vitamin fortifications 

 had made possible the "complete" dry pelleted feeds as we know them to- 

 day. 



Fish feeds manufactured in the form of dry pellets solved many of the 

 problems of hatchery operations in terms of feed preparation, storage, and 

 feeding. There are several additional advantages to pellet feeding. Pellets 

 require no preparation at the hatchery before they are fed. They can be 

 stored for 90-100 days in a cool, dry place without refrigeration. When a 

 fish swallows a pellet, it receives the ingredients in proportions that were 

 formulated in the diet. There is evidence that fish fed dry pellets are more 

 similar in size than those fed meat-meal. The physical characteristics of the 



