B. E. March

Processing of canola meal for incorporation in trout and salmon diets

Canola meals (two commercial meals and one low-heat meal) were processed to reduce fiber content, then washed with selected solvents to reduce the content of antinutritional substances and further concentrate protein. The meals, fiber-reduced meals, and washed meals were used to provide 40% of total protein (26–38% of feed) in the diets of 6-g rainbow trout for 3 weeks or 25% of total protein (21–31% of feed) in the diets of 23-g chinook salmon for 11 weeks. Air-desolventized (low-heat) canola meal, as compared to commercial meal, provided no protein quality advantage in trout feeds. Fiber reduction processing of commercial meal increased meal protein content by 11–16% and reduced crude fiber by 23–50%, but did not have any effect on the quality of protein for trout or salmon. Solvent-washing of fiber-reduced meal improved fish response to canola meal, probably due to reduced glucosinolate content, but possibly also due to reduced sinapine content and alterations in protein availability. Protein concentration was increased by 25–40% by washing, and glucosinolate concentration was reduced by 40–90%.

Intestinal absorption of astaxanthin, plasma astaxanthin concentration, body weight, and metabolic rate as determinants of flesh pigmentation in salmonid fish

Abstract Experiments were conducted to determine whether poor intestinal absorption of astaxanthin or some other metabolic factor is primarily responsible for pigmentation failure in white chinook salmon and small juvenile fish of other salmonid species. None of the fish studied failed to absorb astaxanthin from a single oral dose of the pigment. Intensity of flesh pigmentation in coho ranging in weight from 30–400 g, and fed a diet supplemented with astaxanthin, was significantly correlated with body weight. There was no correlation, however, between flesh colour and plasma astaxanthin concentration or between body weight and plasma astaxanthin concentration. Dietary triiodothyronine reduced both flesh pigmentation and plasma astaxanthin. It is concluded that poor flesh pigmentation results from rapid metabolism of absorbed pigment to colourless derivatives rather than from failure of the fish to absorb pigment.

Muscle Pigmentation and Plasma Concentrations of Astaxanthin in Rainbow Trout, Chinook Salmon, and Atlantic Salmon in Response to Different Dietary Levels of Astaxanthin

Abstract Pigmentation development was studied in rainbow trout Oncorhynchus mykiss, chinook salmon O. tshawvytscha, and Atlantic salmon Salmo salar fed similar practical diets supplemented with 40, 70, or 100 mg astaxanthin/kg of diet. The initial mean body weights of the respective species were 158, 198, and 191 g. The rainbow trout were reared in freshwater at 6.0–11.3°C, the chinook salmon in seawater at 8.8–14.4°C, and the Atlantic salmon in seawater at 7.1–12.7°C. The response of flesh pigmentation to dietary pigment was most rapid in rainbow trout and slowest in Atlantic salmon. Chinook salmon showed the greatest variation in response to the different dietary concentrations of astaxanthin, followed by rainbow trout and Atlantic salmon. In both rainbow trout and Atlantic salmon, pigmentation was most intense in the distal section and decreased anteriorly. In chinook salmon, pigmentation was most intense in the midsection, followed by the anterior section and then the distal section. Postprandial plas...

Carotenoid pigmentation in two strains of chinook salmon (Oncorhynchus tshawytscha) and their crosses

Abstract In order to study the inheritance of flesh pigmentation in chinook salmon, a 6×6 factorial cross was set up by fertilizing eggs from three white (W)- and three red (R)-fleshed chinook salmon with milt from three W- and three R-fleshed salmon to give 36 full-sib families. During the last 7 months before colour-scoring all fish were fed a diet supplemented with astaxanthin added in an oil carrier. Flesh pigmentation was measured against a colour fan at approximately 120 weeks of age and scored on a scale of 1–8. Progeny from RR matings were more pigmented than progeny from WW matings and the pigmentation in the progeny from the crosses was more dependent on the pigmentation of the dam than the sire. There was no significant correlation between the degree of pigmentation and the lipid concentration of the flesh. The results demonstrated that chinook salmon, fed the same diet containing astaxanthin, may show wide variation between strains as well as among families within strains in ability to utilize the dietary pigment. Such heterogeneity among parents within strains suggests that the expression of pigmentation is controlled by a small number of genes with large non-additive effects.

Techniques for evaluation of dietary protein quality for the rainbow trout (Salmo gairdneri)

Abstract Selection of the test fish for uniformity of body weight allowed bioassays for protein quality to be conducted within a 3-week period with small numbers of fish. Slope-ratios from the linear responses of body weight gain to graded levels of protein intake gave practical comparisons of the quality of protein sources. The use of different dietary concentrations of protein sources under test may indicate responses to factors other than those associated with protein per se. The slope-ratio technique lends itself to simultaneous estimations of the relative efficiency of protein energy utilization, which are important in evaluation of plant protein concentrates.

Communications: A Method for Assessment of the Efficacy of Feed Attractants for Fish

Abstract A procedure is described for the testing of feeding response to dietary attractants by juvenile rainbow trout Oncorhynchus mykiss, The fish were maintained in a controlled environment with minimum visual and auditory stimulation. They were fed once daily following a scotoperiod of 12 h. Feed consumption was recorded over a period of 4 min at successive 1-min intervals. The feeding response could be assessed as early as 2 min after dispensing feed. The attractants examined to test the procedure were hydrolysates of krill, These were supplied to the control diet in liquid or dried form, as a component of the pellets or as a surface dressing. There was a positive response to the krill hydrolysate, which was greater when the attractant was applied to the surface of the pellets. Incidental to the development of the technique was the observation that the use of feeding attractants may modify feeding behavior to reduce feed wastage, The technique affords a rapid, sensitive, and repeatable method for eva...

A comparison of survival and growth of two strains of chinook salmon (Oncorhynchus tshawytscha) and their crosses reared in confinement

Abstract The growth rate and survival of the Capilano (hatchery) and Harrison (wild) strains of chinook salmon ( O. tshawytscha ) of British Columbia and their hybrids reared in confinement were compared both during the fresh-water phase and the sea-water phase. Eggs stripped from the Capilano females had better fertility, fingerlings of the Capilano strain were heavier at 25 weeks of age and had a higher average specific growth rate. The Capilano fish were also heavier both in live weight and gutted weight after 1.5 years in sea-pens. No heterosis was detected for any of the traits measured. Cross-means for body weight and specific growth rate tended to be similar to the strain-of-sire mean.

The effect of storage temperature and antioxidant treatment on the chemical and nutritive characteristics of herring meal

The effects of storage temperature and antioxidant treatment on the chemical and nutritive properties of herring meal were studied. The following observations were made:1.Low-temperature (−20°C.) storage promoted more rapid decrease in ether extractability and in iodine value of the ether extract than did storage at 25.5°C.2.Antioxidant treatment prevented the decrease both in ether extractability and iodine value of the extract.3.Binding of the lipid into a complex from which the lipid was extractable with acetone only after HC1 treatment occurred early in the storage period. After six weeks the amount of lipid in this fraction decreased, presumably as a result of further oxidation and polymerization into more refractory compounds.4.Pepsin digestibility tests showed that BHT-treated meal contained the lowest amounts of undigestible nitrogen. Meals subjected to −20°C. contained the most undigestible nitrogen.5.All meals were similar in nutritive value as protein or vitamin-B supplements in chick diets, composed of natural ingredients, even after storage for nine months. As the sole source of protein in a purified diet, the meal kept at −20°C. from time of processing promoted slower growth than the other meals.

Reticulocytosis in Response to Dietary Antioxidants

Alpha-tocopheryl acetate, 1, 2, dihydro-6-ethoxy-2, 2, 4-trimethylquinoline, and butylated hydroxytoluene increased the number of circulating reticulocytes when added to the diet of chickens. Hematocrit values were not reduced and erythrocyte life-spans were not shortened by the antioxidants. The reticulocytosis is attributed to delayed loss of reticular material from the maturing erythrocytes. components.

THE EFFECT OF NUTRITION ON MORTALITY FROM LEUKOSIS IN CHICKENS INOCULATED WITH STRAIN RPL-12 AVIAN LEUKOSIS VIRUS.

A previous paper (1) reported that the incidence of avian leukosis was greater in chickens maintained on a high plane of nutrition. Although suboptimal nutrition has generally been demonstrated to inhibit tumor induction and growth (12), the data in the earlier paper suggested that nutritional excess increased susceptibility to infection with avian leukosis and/or favored tumor development rather than that nutritional deficiency had the converse effect. In the experiments reported previously, infection was the result of natural exposure in an environment in which the disease was endemic. The present paper presents results obtained when chicks fed different diets were injected with strain RPL-12 avian leukosis virus (4). Hill and Garren (5) found that susceptibility of chicks to transplanted RPL-12 tumor could be influenced by calcium and phosphorus levels in the diet. Olson et al. (9) reported that the feeding of a particular lot of cod liver oil increased the incidence of lymphomatosis in chickens exposed to infection by contact with infected chickens or by intraperitoneal injection of RPL-12 virus.