Growth, nitrogen metabolism and fat metabolism in Salmo gairdneri, rich

Abstract

• 1.

  1. Studies of growth and nitrogen balance were made on individual fish. The effects of temperature and diet change were investigated.

• 2.

  2. Feeding a low fat content diet tended to confirm the finding of other workers that 12°C is approximately the optimum temperature for trout growth.

• 3.

  3. 12°C is a compromise between efficient absorption in the gut and high energy demands at 16°C, and an inefficient absorption and low energy demands at 8°C.

• 4.

  4. Feeding high content diets resulted in fish at 16°C showing greater growth rates than those kept at 12°C.

• 5.

  5. Accompanying this, there was a greater reduction in ammonia excretion and a higher proportion of ingested nitrogen was retained for growth.

• 6.

  6. With temperature rise, a greater percentage of ingested fat was absorbed by the fish.

• 7.

  7. In these diets, fat replaces nitrogenous compounds as an energy source, and increasingly so with rise in temperature.