Physiological Responses Of Rainbow Trout Research Articles

EFFECT OF PROPYLENE GLYCOL ON FEED DIGESTIBILITY AND THE GROWTH AND PHYSIOLOGICAL RESPONSE OF RAINBOW TROUT

The effect of supplementing from 0 to 10% propylene glycol (replacing corn starch on an equal weight basis) to a low-energy trout diet on the feed digestibility and the growth and physiological response of rainbow trout was determined. Propylene glycol had no significant effect on the growth, feed:gain ratio, final carcass composition and feed digestibility coefficients of the trout. However, propylene glycol was apparently unstable and/or volatile during feed processing and storage which may have confounded a clear interpretation of the digestibility and growth studies. The trout reared on the 10% propylene glycol supplemented diet also had a slower feeding response than the other groups which may ultimately affect the growth of the trout. It was concluded that propylene glycol was not a cost effective source of dietary energy to the trout and a level of 10% in the diet appeared to be tolerated by the trout. Key words: Trout, propylene glycol, energy, feed utilization, digestibility

Physiological responses of rainbow trout in a pulp and paper mill recipient during four seasons

The toxicity of pulp and paper mill effluents was estimated by exposing rainbow trout to the effluents in situ during four seasons. The experiments were carried out using one control group and three test groups at different distances from the discharge. After a 10-day exposure mainly hematological parameters were determined from the caged fish. The caging site affected most of the 15 parameters analyzed (blood Hct, MCHC, erythrocyte, and leucocyte counts; plasma gluc, prot, urea, Ca 2+, Mg 2+). Some changes were detected even at the farthest caging site, 8 km from the discharge. The time of year strongly influenced the results. Seasonal variation exceeded the variation caused by caging site. In addition, the season influenced the responses of rainbow trout to the effluent in many parameters. None of the responses detected were observed in all the experiments. The only significant changes in the median values of the parameters from the caging experiments were a decrease in the plasma Mg 2+ and an increase in the plasma K + concentration.

Histopathological and physiological responses of rainbow trout ( Salmo gairdneri richardson) to sublethal levels of lead

Rainbow trout ( Salmo gairdneri) were exposed to sublethal levels of water-borne or dietary lead for 32 weeks. The study included a histopathological assessment of all organs, examination of red cell morphology, and a comparison of oxygen consumption in liver homogenates from exposed and control fish. No effects of lead toxicity were noted in these parameters. The most sensitive and reliable indicator of lead toxicity was the development of black tails and spinal curvature. These changes were observed in 30% of trout exposed to 120 ± 31 μg Pb 1 −1 of water-borne lead after 30 weeks. No other effects of lead toxicity were noted.

Response of rainbow trout (Salmo gairdneri) to increased levels of available carbohydrate in practical trout diets.

1. The physiological response of rainbow trout (Salmo gairdneri) reared on different levels of available carbohydrate in practical trout diets having the same levels of energy and nitrogen for 16-24 weeks was determined. 2. Weight gain was significantly reduced in trout reared on the highest level of available carbohydrate, 210 g cerelose (alpha-glucose) kg, and there was a significant linear regression (R2 0.88 of dietary carbohydrate on weight gain. 3. Liver: body-weight values and liver glycogen levels increased in relation to increased dietary carbohydrate. 4. Liver glucose-6-phosphate dehydrogenase (EC 1.1.1.49) activity increased and liver phosphoenolpyruvate carboxykinase (EC 4.1.1.32) activity decreased per kg body-weight of fish with increasing dietary carbohydrate. However, no significant effect was noted on the activity of these liver enzymes above a dietary cerelose level of 140 g/kg. 5. Liver fructose diphosphatase (EC 3.1.3.11) activity increased with increasing dietary carbohydrate has been interpreted as meaning a recycling of triosephosphate to glucose-6-phosphate. 6. Dietary carbohydrate level had no significant effect on the liver pyruvate kinase (EC 2.7.1.40) activity, the rate of glucose utilization or the percentage conversion of [14C]alanine to glucose in the plasma of trout. 7. The results indicate that rainbow trout have a limited ability to adapt to increased dietary carbohydrate and a level in excess of 140 g/kg of the diet is not efficiently utilized.

Effect of extrusion processing and steam pelleting diets on pellet durability, pellet water absorption, and the physiological response of rainbow trout ( Salmo gairdneri R.)

The effect of extrusion processing and steam pelleting on pellet durability, pellet water absorption and the physiological response of rainbow trout reared upon these diets was investigated. Extruded pellets were observed to be more durable, had superior water stability and absorbed more water than steam pellets. Trout reared on extruded pellets had prolonged gastric emptying in comparison with those reared on steam pellets; this may have been responsible for the reduction in daily feed consumption. Trout reared on extruded pellets also showed significantly lower weight gain but higher feed efficiency than those reared on steam pellets. Liver: body weight ratio and percent liver glycogen were significantly higher in trout reared on the estruded pellets as compared with those reared on steam pellets. Thus, extrusion processing may increase the bioavailability of carbohydrate in the diet and the enlarged livers and increased liver glycogen content could impair liver function.

Physiological Response to Hooking Stress in Hatchery and Wild Rainbow Trout (Salmo gairdneri)

Abstract This study evaluated the physiological response of rainbow trout to hooking stress after being played under standardized conditions (0–5 min) and estimated the time needed for recovery (to 72 h). Plasma osmolality and chloride measurements were used to evaluate osmoregulatory disturbances and gill ion-exchange function, and plasma glucose was used as an index of the generalized nonspecific physiological stress response. Hooking stress caused more severe blood chemistry differences in hatchery fish than in wild trout. Also, hooking stress imposed a greater stress on larger than on smaller hatchery rainbow trout. Higher water temperatures aggravated the delayed hyperglycemia and hyperchloremia in both hatchery and wild trout but only about 3 days were needed for recovery at 4, 10, or 20 C.