B.S. Dosanjh

Potential for dietary phytase to improve the nutritive value of canola protein concentrate and decrease phosphorus output in rainbow trout (Oncorhynchus mykiss) held in 11°C fresh water

This study assessed the potential for using dietary phytase to improve the nutritive value of canola protein concentrate (CPC) for rainbow trout, and to concomitantly minimize phosphorus discharge into the environment. Eight diets were prepared. LT-anchovy meal (AM) provided 89% of the protein in the basal diet, whereas in the remaining diets, 59% of the protein originated from CPC by replacement of AM protein. Four CPC diets were supplemented with phytase (Natuphos®) at levels of either 0, 500, 1500 or 4500 phytase units (FTU)/kg diet together with 4505 mg/kg phosphorus. Two CPC diets contained 1500 FTU/kg and either 0 or 2253 mg/kg of supplemental phosphorus. The seventh CPC diet contained no phytase or supplemental phosphorus. A commercial trout feed served as an industry control. All diets were fed to triplicate groups of rainbow trout (initial weight, 17.9 g) to satiation daily for 84 days. Mean water temperature was 11.0°C. The level of phytic acid degradation and the apparent availability of dietary phosphorus were ascertained for all groups. Fish fed the CPC diets, regardless of their phytase and phosphorus levels, exhibited growth rates, feed efficiencies and protein utilization comparable to those of control fish. There was, however, a clear positive dose-response of phytase on dietary phytate digestibility and phosphorus availability was improved significantly by the highest level of phytase. We conclude that dietary phytase has potential to improve the nutritive quality of CPC for rainbow trout and the availability of phytate phosphorus.

Digestibility of various feedstuffs by post-juvenile chinook salmon (Oncorhynchus tshawytscha) in sea water. 1. Validation of technique

Abstract This study was undertaken to assess whether the Guelph system for measuring digestibility in rainbow trout in fresh water was suitable for determining digestibility in chinook salmon held in sea water. Feces were collected from chinook salmon by the Guelph system, the stripping technique (once per week) and intestinal dissection. Validation of the Guelph procedure also involved assessment of: (1) the digestibility coefficients based on total fecal collection versus those based on the indirect chromic oxide indicator method, (2) the extent of nutrient leaching when using the Guelph system, and (3) the effect of level of dietary intake and extent of fish handling (due to stripping of feces) on estimates of nutrient digestibility by the Guelph method. No significant differences were found between the complete collection and indicator methods for measuring apparent nutrient digestibilities. Apparent digestibility values calculated using feces collected directly from the fish by both stripping and dissection were consistently lower than the complete collection and indicator values derived using the Guelph system. The stripping technique yielded the lowest digestibility coefficients. Nutrient leaching occurred when the feces had been exposed to sea water for more than 6 h. This was attributed to incomplete entry of feces into the collection column. Fish handling and concomintant reduction of food intake depressed digestibility coefficients for nutrients and energy and increased fish mortality. It is concluded that the Guelph system of fecal collection involving the use of Cr 2 O 3 as the indigestible marker is a potentially reliable digestibility procedure for chinook salmon in sea water. However, care must be exercised to ensure rapid and complete removal of feces to the collection column to minimize nutrient leaching.

Digestibility of various feedstuffs by post-juvenile chinook salmon (Oncorhynchus tshawytscha) in sea water. 2. Measurement of digestibility

Abstract This study was undertaken to determine the digestibility of organic matter, crude protein, and gross energy, in selected animal and plant feedstuffs using post-juvenile chinook salmon held in running 8–12.5°C filtered sea water (28–31 ppt) on a natural photoperiod. Feces were collected by either a modified Guelph procedure, stripping or intestinal dissection using chromic oxide as the indigestible marker. Most fishmeal sources contained more digestible energy for chinook salmon than did the other test animal and plant protein sources. Two sources of poultry by-product meal differed markedly in percentages of digestible protein and energy. Blood meal, which was dried in a continuous dryer, had very low percentages of available protein and energy. A commercial source of canola meal, one source of glucosinolate-free canola meal and rapeseed protein concentrate were all well digested. The digestibility of commercial sources of soybean meal and soybean protein isolate could not be ascertained accurately because fish fed test diets containing these protein sources exhibited poor appetite. The energy in extruded wheat was absorbed much better than that in wheat middlings. The Guelph system of fecal collection appeared to provide reliable estimates of feedstuff digestibility using chinook salmon in sea water.

Assessment of undephytinized and dephytinized rapeseed protein concentrate as sources of dietary protein for juvenile rainbow trout (Oncorhynchus mykiss)

Abstract This study was undertaken to evaluate three sources of rapeseed protein concentrate (RPC) as partial or total replacements of steam-dried whole herring meal (HM) in a practical diet for juvenile rainbow trout. Groups of 4.2–4.4 g trout held in 10.0–10.3°C well water on a natural photoperiod were fed one of 10 isonitrogenous (43% protein) and isoenergetic (21.6 MJ gross energy/kg) diets to satiation 3 times daily. Each of three test protein sources, viz. undephytinized, untreated control RPC (UDC), undephytinized solvent-treated control RPC (UDSC), and dephytinized RPC (DP), comprised about 19.0, 39.0 and 59.0% respectively of dietary protein by replacement of one-third (L), two-thirds (M) and all (H) of the HM protein in the control diet. Rainbow trout growth rate, feed intake, feed efficiency, protein and gross energy utilization, mortality and health were not compromised when either UDC or DP replaced up to 66% of HM protein in the control diet. Total replacement of HM protein with each of the RPC sources did not depress feed intake, but did significantly reduce growth rate, feed efficiency, and protein and energy utilization. The procedure used to dephytinize RPC lowered RPC protein quality. Whole body concentrations of calcium and phosphorus were inversely related to the dietary levels of UDC and UDSC. Body levels of zinc were significantly depressed in fish fed the diet with UDSC-H. Fish fed diets with DP displayed normal mineral levels. Significant elevation of thyroid follicle epithelial cell heights was found only in those groups fed the diets with UDC-H or UDSC-H. Whole body proximate composition was generally uninfluenced by diet treatment. It is concluded that RPC can comprise 39% of the dietary protein (fish meal only 11%) for rainbow trout without adversely affecting performance. Nutritional strategies that may enable complete replacement of fish meal protein in diets for rainbow trout by RPC are outlined.

Evaluation of Tower and Candle rapeseed (canola) meal and Bronowski rapeseed protein concentrate as protein supplements in practical dry diets for juvenile chinook salmon (Oncorhynchus tshawytscha)

Abstract A laboratory study and a pilot-scale hatchery experiment were carried out to determine the acceptability of rapeseed products as protein supplements in diets for chinook salmon. Replacement of 10 and 13% of the protein in a modified Abernathy dry diet with protein from Tower or Candle rapeseed meal or Bronowski rapeseed protein concentrate did not alter growth rate, food or protein utilization, body composition, thyroid or pituitary cytology, osmoregulatory capacity, health or mortality of chinook salmon. However, growth rate and food (protein) utilization were reduced when 25% of protein was replaced by rapeseed meal, but not when replaced by Bronowski rapeseed protein concentrate. Condition factors of chinook fed rapeseed products at the intermediate or highest levels were often significantly elevated. Hatchery performance of chinook salmon fed a dry diet where 13% of protein was provided from Tower meal was similar to that when Oregon moist pellets were fed except for a compensatory increase in thyroid activity in the former fish. It is concluded that rapeseed products of the canola type are good protein supplements for chinook salmon and can comprise 13 to 16% of dietary protein (16 to 20% of dietary dry matter).

Influence of dietary blends of menhaden oil and canola oil on growth, muscle lipid composition, and thyroidal status of Atlantic salmon (Salmo salar) in sea water

The effects of various dietary blends of menhaden oil (MO) with canola oil (CO) on the growth performance, whole body proximate composition, flesh quality (muscle proximate and lipid composition) and thyroidal status of immature Atlantic salmon in sea water were studied.Atlantic salmon (initial weight, 145.2–181.3 g), held on a natural photoperiod and in 1100 L fibreglass tanks that were supplied with running, aerated (D.O., 9–10.5 p.p.m.), ambient temperature (8–10.5 °C) sea water (salinity, 28–30‰), were fed twice daily to satiation one of four isonitrogenous (∼36% digestible protein) and isoenergetic (∼18.8 MJ of digestible energy kg-1) extruded high-energy diets for 112 days. All diets contained omega –3 (n-3) fatty acids in excess of requirements and differed only with respect to the source of the supplemental lipid which was either, 25% MO; 20.75% MO and 4.25% CO; 16.5% MO and 8.5% CO; or 12.25% MO and 12.75% CO. Thus, CO comprised, respectively, 0, 15.5, 31.2, or 47.0% of the total dietary lipid content (∼28% on an air-dry basis).Dissimilar percentages of saturated fatty acids in the dietary lipids were not found to be consistently related to the apparent gross energy digestibility coefficients of the diets. Atlantic salmon growth, dry feed intake, feed and protein utilization, percent survival, thyroidal status, and whole body and muscle proximate compositions were generally not influenced by the different sources of supplemental lipid. Therefore, our results suggest that canola oil may comprise as much as 47% of the lipid in high-energy grower diets for Atlantic salmon without compromising performance.The muscle lipid compositions generally mirrored those of the dietary lipids which, in turn, were influenced strongly by the concentrations and compositions of the CO and MO in the diet. Hence, as the dietary CO level was increased there were attendant increases in percentages of oleic acid (18:1(n-9)), linoleic acid (18:2(n-6)), total omega-6 (n-6) fatty acid content, and ratios of (n-6) to (n-3) and decreases of eicosapentaenoic acid (EPA; 20:5(n-3)), docosahexaenoic acid (DHA; 22:6(n-3)) and n-3 HUFAs (EPA & DHA) in the flesh lipids. The ranges for percentages of saturated and unsaturated fatty acids in the flesh lipids were, however, much less than those noted respectively in the dietary lipids probably because of selective metabolism of many of the former acids and some of the 18 carbon unsaturates for energy purposes.

Preliminary evaluation of canola oil, pork lard and marine lipid singly and in combination as supplemental dietary lipid sources for juvenile fall chinook salmon (Oncorhynchus tshawytscha)

Abstract Canola oil, pork lard and herring oil singly and in various combinations were assessed as supplemental sources of dietary lipid for juvenile fall chinook salmon held in running, aerated 10–12°C well water on a natural photoperiod for 62 days. Each of the six different types of supplemental lipid comprised about half of the total lipid content (16% of dry matter) in an experimental dry diet (West Van 32). Some groups received Oregon Moist Pellets (OMP), a practical hatchery diet. Thereafter, the performance of the groups was evaluated in running, aerated 10–14°C seawater for 35 days when all fish received OMP. The type of supplemental dietary lipid did not significantly influence fish growth in freshwater. All groups fed the test dry diets had significantly higher food and protein conversion than those receiving OMP. Best overall food and protein utilization occurred in fish fed West Van 32 supplemented with canola oil or an equal mixture of herring oil with canola oil or lard. Mortality was negligible in all groups. Body lipid composition generally mirrored that of dietary lipids except (1) percentages of docosahexaenoic acid (C22:6ω3) were higher in body lipids than in dietary lipids, (2) groups receiving supplemental canola oil (C), lard (L) or a combination of these sources (C-L) had elevated percentages of ω3 fatty acids in their body lipids and, (3) the range for percentages of saturated fatty acids in body lipids (15.7–22.8%) was smaller than that noted for dietary lipids (12.5–29.5%). None of the groups showed any ability to metabolically convert dietary linoleic acid (C18:2ω6) to arachidonic acid (C20:4ω6). However, contrary to other studies on rainbow trout and coho salmon, the fall chinook salmon in this study metabolically adapted to a high dietary level of ω6 fatty acids (2.6% or 16.2% of dietary lipid level) when the diet simultaneously contained 2.7% ω3 fatty acids. Nutritional history in freshwater did not compromise performance in seawater when all groups received OMP. Also, the body lipid compositions of the test groups were transformed to reflect that of OMP after 35 days of seawater culture. It is concluded that canola oil, pork lard and a blend of these lipid sources are potentially excellent alternative types of supplemental dietary lipid for juvenile fall chinook salmon destined for ocean release.

Protein quality of Altex canola meal for juvenile chinook salmon (Oncorhynchus tshawytscha) considering dietary protein and 3,5,3′-triiodo-L-thyronine content

Abstract Juvenile chinook salmon, reared in freshwater, were fed isocaloric dry diets varying in protein (29, 39 and 49%), Altex canola meal (0, 11.5 and 23% of dietary protein by replacement of fish meal) and 3,5,3′-triiodo-L-thyronine (T 3 ; 0, 5 and 25 ppm) content. Oregon moist pellets (OMP) served as a reference control diet. Fish were subsequently observed in seawater while fed OMP. The nutritive value of herring and canola meal was similar when diets contained 29 and 39% protein, but not when protein content was 49%. Chinook fed 49% protein diets grew significantly faster than those fed diets with 29% protein. Appetite and protein utilization were inversely related to dietary protein content. Chinook fed OMP grew faster than those fed 49% protein diets with canola meal, but not when canola meal was deleted. T 3 stimulation of growth of chinook fed 49% protein diets was positively correlated with the dietary concentration of canola meal and T 3 . Dietary and hormonal treatment in freshwater did not influence chinook performance in seawater. Further, thyroid hypertrophy observed in fish fed diets with canola meal during freshwater residency did not persist after 5 weeks in seawater. It is concluded that Altex canola meal may comprise almost 25% of dietary protein without adversely influencing protein quality, provided that dietary glucosinolate content is below 2.65 μmoles/g dry diet (300 μg/g as 3-butenyl isothiocyanate). Dietary canola meal concentrations of 30% of dry matter (glucosinolate content > 2.65 μmoles/g dry diet) can be employed if 5 ppm of T 3 are administered simultaneously.

Efficacy of canola oil, pork lard and marine oil singly and in combination as supplemental dietary lipid sources for juvenile coho salmon (Oncorhynchus kisutch)

Abstract Canola oil, pork lard and herring oil singly and in combination were assessed as supplemental sources of dietary lipid for juvenile coho salmon held at 10–12°C on a natural photoperiod over an 84-day period. Each of the six different types of supplemental lipid comprised about 56% of the lipid content (15% of dry matter) in an experimental dry diet (West Van 1). Some groups received Oregon moist pellets (OMP) which is presently the standard hatchery diet. All groups were fed twice daily to satiation. Relative to coho fed West Van 1 with marine oil alone, type of supplemental lipid did not influence coho growth, food, protein and energy utilization, body proximate composition, fish health or survival, or the histological structure of selected organs. Coho fed OMP grew significantly faster than those fed West Van 1 supplemented with lard or mixtures of canola oil with herring oil or lard due to increased appetite. Body lipid composition mirrored that of dietary lipids except levels of saturated and unsaturated fatty acids showed less variation than those in dietary lipids. It is concluded that canola oil, pork lard and a blend of these lipid sources are excellent alternative types of supplemental dietary lipid for coho salmon under our test conditions. They are more available, often less expensive, and less prone to oxidation than marine oil.

Effects of dietary lipid and carbohydrate levels and chronic 3,5,3'-triiodo-L-thyronine treatment on growth, appetite, food and protein utilization and body composition of immature rainbow trout, Oncorhynchus mykiss, at low temperature

Abstract Twelve dietary treatments were each given to duplicate groups of immature rainbow trout held at 6–7 °C for 12 weeks. Three isonitrogenous (protein = 39%) and isocaloric (3905 kcal digestible energy/kg) diets which varied in their proportions of lipid to carbohydrate (17.6%/1.48%;13.1%/14.9%;7.4%/28.3%) were each supplemented with 0, 4, 8 or 12 ppm T 3 (3,5,3′-triiodo-L-thyronine). All fish were fed their prescribed diet by hand to satiation four times daily. As the ratio of lipid to carbohydrate decreased, growth rate (weight and length), condition factor, food intake, gross food conversion efficiency (GFCE) and protein efficiency ratio (PER; dry basis) decreased. By contrast hepatosomatic index (HSI), plasma glucose concentration, carcass water content and percent lipid deposited increased. Growth was not depressed significantly by inclusion of 13.4% cerelose (D-glucose monohydrate) in the diet but was when 26.8% cerelose was added. All supplemental T 3 doses significantly enhanced growth in weight and length. However, while 8 or 12 ppm T 3 completely offset the reduced growth in length of trout ingesting the high carbohydrate diet, these doses only partially counteracted diminished growth in body weight. Consequently, the condition factor declined. T 3 treatment increased food intake (g/fish) in proportion to body weight which resulted in no change in appetite on a body weight basis. Likewise, percentages of protein and lipid deposited and GFCE were not significantly influenced by T 3 administration. By contrast, feed efficiency and PER values (wet weight basis) were improved significantly by 8 or 12 ppm T 3 in the diet. In conclusion, T 3 administration was efficacious in stimulating skeletal growth of trout at low temperature, and it is especially noteworthy that the hormone completely offset the reduced linear growth of trout receiving a high proportion of carbohydrate in their diet under out test conditions. The mechanism for this effect may have involved synergism of T 3 with growth hormone and/or improvement of carbohydrate utilization, since in the latter case plasma glucose level and HSI were respectively increased and decreased by T 3 treatment.