Einar Lied

Starch as an energy source in feed for cod (Gadus morhua): Digestibility and retention

Abstract An experiment was set up to determine whether cod, Gadus morhua , could use pre-cooked potato starch as an energy source. Four energy levels (0%, 10%, 20% and 30%) of carbohydrate with a constant fat content were fed for 8 weeks. The digestion capacity for pre-cooked potato starch decreased from 40% to 26% with increasing amount of carbohydrate, the average being 33%. The digestibilities of protein and fat were independent of the starch content in the feed. The protein intake was similar for all groups. Energy intake increased when the level of carbohydrate in the feed increased. Neither growth values nor retention values for protein and fat indicated that carbohydrate was utilized to any significant degree as a source of energy. Plasma glucose increased from 350 mg/l to 800 mg/l as the carbohydrate increased from 0 to 30%, and the average was 530 mg/l. The glycogen deposition in muscle tissue seemed to reach a level of ca. 0.4% of muscle wet weight in all groups. The glycogen deposition in the liver attained a maximum of 3.5% of liver wet weight.

Nutrient absorption and growth of Atlantic salmon (Salmo salar L.) fed fish protein concentrate

Absorption of amino acids was studied in Atlantic salmon fed moist diets where 0, 15 and 30% of the fish meal protein was replaced with concentrated fish silage protein prepared from whole minced herring or herring fillet offal (Clupea harengus). Blood samples were withdrawn at 0, 3, 6, 12, 24, 48 and 72 h post-feeding, and plasma-free amino acid concentrations were compared to those of fish deprived of food for 48 h. Fish fed fish protein concentrate showed similar or higher plasma amino acid concentrations than fish fed diets without any added fish protein concentrate. Maximum plasma amino acid concentrations occurred 3–12 h post-feeding, being fastest in fish fed the most soluble protein source. Effects of inclusion levels on growth and nutrient utilisation were studied in two experiments where either 0 to 30% or 0 to 40% of the fish meal protein was replaced with the fish protein concentrates tested. Fish fed diets where less than 15% of the fish meal protein was replaced by fish protein concentrate showed better growth compared to fish fed either none or higher inclusion levels. Protein accretion decreased in fish fed the high inclusion levels, and remained unaffected by lower inclusion levels. Protein synthesis measured as incorporation of labelled lysine was not significantly affected by the fish protein concentrate inclusion. It is assumed that the better growth obtained might be due to a lower protein breakdown.

Liver retention of fat and of fatty acids in cod (Gadus morhua) fed different oils

Abstract Duplicate groups of cod were fed, for 8 weeks, diets in which 48% of the available energy came from either cod liver oil, Greenland halibut oil or peanut oil. The hepatosomatic index of the fish increased from 9.5% to an average of 13%, and the liver fat content from 55% to 67–70%. The average liver retention of the absorbed fat was 60%. Corresponding fatty acid retentions were calculated for most major fatty acids, showing a general non-specific retention. Exceptions were increased values for 16:0, 18:0 and 18:1, assumed from de novo synthesis, and decreased retentions for 14:0, 22:1 and 18:4 fatty acids. The fatty acid composition of the dietary fat had a strong influence on the composition of liver triglycerides, which constitute the main fat depot in cod, and also affected the composition of polar lipid fatty acids in liver and muscle.

Feed optimization in atlantic cod (Gadus morhua): Fat versus protein content in the feed

Abstract Two feeding experiments were performed with cod. One involved 40-g fish fed for 26 days and the other 180-g fish fed for 60 days. Feeds based on squid mantle, capelin oil and dextrinized potato starch were made up to give from 75% to 27% of available protein energy, balanced with from 11% to 61% fat energy, all with 12–15% carbohydrate energy. In the second experiment, three groups of fish were fed each day, and three groups every third day, whereas in the first experiment all fish were fed five days a week. Relative growth, feed conversion, digestibilities and retentions of protein and fat were determined. Protein retentions were calculated as PER (live weight gain over protein intake) and PPV (protein gain over protein intake). The apparent digestibilities for protein and fat were above 90%, except for a diet with 61% available energy from fat. The protein-sparing effect of fat seemed to be low in cod, and 26% to 29% of protein was retained, as compared with 50% to 60% of fat, except for groups on a very low-fat diet or on reduced feeding frequency. Dietary lipid was deposited as liver fat, and a linear relation between the liver index and the fat intake was demonstrated. It was concluded that PPV is a more appropriate index for growth than PER in studies on a lean fish such as cod with a low-fat fillet and a fatty liver. A reduced feeding frequency had no effect on feed conversion and PER whereas the weight gain and PPV were reduced. Based on these experiments optimal growth for cod may be achieved with a feed giving available energy concentrations of 60%, 25% and 15% from protein, fat and carbohydrate, respectively, fed every day.

Enzymatic hydrolysis of by-products from the fish-filleting industry; chemical characterisation and nutritional evaluation.

Fish frames without heads from Atlantic cod and Atlantic salmon were proteolysed with the industrial enzymes neutrase®, alcalase® and pepsin for 1, 15, 30, 45, 60, 90 and 120 min. After 120 min of hydrolysis, salmon treated with alcalase and cod treated with pepsin yielded significantly (p < 0.05) higher protein recoveries (67.6 and 64% respectively) as compared to salmon treated with neutrase or pepsin and cod treated with neutrase or alcalase (53–62%). To minimise bitterness in the fish hydrolysates, kojizyme™ was added after 120 min of pre-hydrolysis with alcalase, and the hydrolysis was run for additional times of 120, 240, 360, 480, 600 and 720 min. Protein recovery did not change significantly during the hydrolysis with kojizyme, but the degree of hydrolysis increased significantly (p < 0.01) in both the cod and salmon hydrolysates. A hydrolysate from cod treated with alcalase (150 min) followed by treatment with kojizyme (510 min) was produced. The final hydrolysate was freeze-dried to a fish protein hydrolysate (FPH) and chemically characterised. The nutritional value of the FPH was established in an experiment with rats. Inclusion of 10% FPH-N showed significantly (p < 0.05) higher nutritional value as compared to rats fed higher inclusion levels of FPH. © 2000 Society of Chemical Industry

Nutrition of Atlantic salmon (Salmo salar); the requirement and metabolic effect of lysine

The aim of the study was to determine the dietary lysine requirement of medium sized Atlantic salmon (376±46 g) given a high energy diet (23.6 KJ g−1) and to see if increased levels of lysine would effect the metabolism of arginine. Zein was used as a major protein source in the experimental diets, which were supplemented with synthetic amino acids to resemble the amino acid pattern of fish meal, with the exception of lysine. Dietary lysine contents ranged from 5.9 to 21.0 g kg−1 dietary dry matter. The requirement of lysine was estimated at 16–18 g kg−1 dry diet or 0.79–0.89g MJ−1 digestible energy. The result was confirmed by a significant increase of free lysine in muscle if excess lysine was added to the diet. Fish fed the highest level of lysine did not increase growth and tended to show reduced levels of arginine and ornithine in plasma and muscle and reduced level of urea in plasma. These findings indicate a metabolic effect on the utilisation of arginine at high dietary levels of lysine. Lysine was also found to inhibit liver arginase of Atlantic salmon in vitro.

Nutrition of Atlantic Salmon (Salmo salar): The Requirement and Metabolism of Arginine

Abstract This experiment was conducted to determine the dietary arginine requirement of medium sized Atlantic salmon (383 ± 62 g) given a high energy diet (26.1 KJ/g). Zein was used as major protein source in the experimental diets supplemented with synthetic amino acids resembling the amino acid pattern of fish meal, with the exception of arginine. Arginine content was 11.3 (2.7), 16.8 (4.0), 20.2 (4.8), 26.0 (6.2), and 28.6 (6.8) g/kg dietary dry matter (% of dietary protein). Expressed in terms of digestible energy the arginine content was 0.53, 0.78, 0.94, 1.21, and 1.33 g/MJ. Protein content on dry weight was 42% in all diets. Weight gain and protein efficiency parameters were together with increasing levels of urea and ornithine in plasma and free arginine in muscle and plasma used to indicate the requirement of arginine. The growth and protein retention obtained indicated that Atlantic salmon has a requirement of arginine of 21.2–21.6 g/kg dietary dry weight (5.0–5.1% of the protein) or 1.0 g/MJ digestible energy. The metabolic parameters indicated a requirement of 20.2 g/kg dietary dry weight (4.8% of the protein) or 0.94 g/MJ. Increased dietary levels of arginine seemed to interact with the tissue free concentrations of several indispensable amino acids.

Growth, feed and nutrient utilisation and gastrointestinal evacuation time in Atlantic salmon (Salmo salar L.): the effect of dietary fish meal particle size and protein concentration

Growth, nutrient utilisation and gastrointestinal evacuation time using different fish meal particle sizes and dietary protein concentration was examined in Atlantic salmon. Salmon were given micro, standard or coarse grounded fish meals at two dietary protein concentrations (30 or 45%) in isolipid diets. Gastric evacuation time was influenced by fish meal particle size. Coarse ground fish meal gave a slower gastric evacuation time compared to finer ground fish meal. Specific growth rate was not influenced by the protein concentration, but there was an adverse effect of coarse ground particles. This effect may be explained by the reduced feed intake of fish fed diets containing coarse ground fish meal. Feed conversion ratio (FCR) or energy conversion ratio (ECR) was reduced with increasing dietary protein concentration. This effect was mainly caused by different energy levels in the diets and not protein/carbohydrate levels. Standard coarse fish meal gave a reduction in ECR, but there was no effect of fish meal particle size on FCR. A protein sparing effect of starch was demonstrated. Productive protein value (PPV) and productive energy value (PEV) was not affected by dietary protein concentration or fish meal particle size. Dietary protein concentration had no effect on nitrogen or fat digestibility but there was a reduction in fat digestibility when coarse ground fishmeal was used in the diets. There were only minor effects on the dressing out percentage, condition factor and fat in cutlet.

Lipid digestion in cod (gadus morhua)

Abstract 1. 1. Cod, 2.6–3.4 kg. were fed a mixed diet of sprat, capelin oil and wheat flour. 2. 2. Lipids from the feed, stomach and four intestinal segments were separated into tri-, di- and monoglycerides and free fatty acids and analysed by GLC. 3. 3. All lipolytic products were concentrated in 14:0, 16:0 and 18:0, up to 60% and extremely low in the ω-3 fatty acids. 4. 4. Residual triglycerides contained 80% of saturated and monoenoic fatty acids. 5. 5. Linoleic acid increased from 2% in feed TG to 10% in TG of the rectum.

Changes in plasma and muscle free amino acids in atlantic salmon (Salmo salar) during absorption of diets containing different amounts of hydrolysed cod muscle protein

1. 1. Atlantic salmon (Salmo salar) were fed three diets of increasingly pre-digested protein for 4 weeks. They were then starved for 2 days, then fed to satiation. 2. 2. Plasma and muscle samples were collected before feeding and 0, 6, 12, 24, 48 and 72 hr after feeding and analysed for free amino acids. 3. 3. Plasma essential free amino acids were significantly higher (P < 0.05) at 6 and 12 hr post-prandial, while the non-essential amino acids were hardly affected. 4. 4. Minor differences were obtained in muscle free amino acids. Maximum concentration was obtained at 24 hr post-prandial in fish fed the control, and at 12 hr post-prandial for both the pre-digested feeds. 5. 5. In both plasma and muscle, total free amino acids were higher in those fed the proteolysed feeds than in those fed the non-proteolysed feed.