Fed Fish Meal Research Articles

Nutrient digestibilities and gut function in Atlantic salmon (Salmo salar) fed diets with cellulose or non-starch polysaccharides from soy

Duplicate groups of Atlantic salmon (Salmo salar), kept in saltwater, were fed fish meal based cold-pelleted diets where graded levels of native or extruded non-starch polysaccharides (NSP) from soybeans replaced cellulose, at a total NSP level of 100 g kg−1 for 28 days. The study also included a diet where defatted soybean meal (SBM) constituted the NSP at a level of 100 g kg−1 and a reference diet without NSP supplementation.The SBM diet resulted in a significant reduction in faecal dry matter content, apparent digestibilities of starch and organic material, and growth, and an increased faecal output of several elements (K, Na, Zn), compared to all the other diets. Morphological changes were only seen in the intestine of the fish fed the SBM, i.e. the diets holding purified soy-NSP did not induce enteritis. When compared to the diet without NSP, cellulose addition increased faecal dry matter, while inclusion of native soy-NSP reduced it. Dry matter in faeces and apparent digestibility of crude protein decreased in a linear manner, while the digestibility of starch and faecal output of K and Na increased linearly when native soy-NSP replaced graded levels of cellulose from 0 to 100 g kg−1 feed. When diets with 75 or 100 g kg−1 of native NSP and extruded soy-NSP were compared, fish fed native soy-NSP had reduced faecal dry matter, higher digestibility of starch, and increased faecal output of Cu, Fe, and K. Dry matter in faeces and faecal output of Cu was lower for the highest inclusion level, while digestibility of starch and faecal output of Mn and K were higher.In conclusion, soy-NSP was inert compared to the fish meal reference, with respect to nutrient digestibilities and intestinal pathologies, but affected faecal mineral excretion in Atlantic salmon.

MARINE MICROALGAE EFFECTS ON ENDOMETRIAL EXPRESSION OF KEY MOLECULES IN PREGNANT DAIRY COWS

Feeding fish meal, high in omega-3 long chain polyunsaturated fatty acids (PUFA) has been shown to inhibit uterine secretion of series 2 prostaglandins and improve pregnancy rates. The objectives of the current study were to evaluate the effects of two sources of long chain omega-3 PUFA supplements, fish oil and marine microalgae, on the expression of key receptors and the prostaglandin H synthase-2 enzyme in bovine endometrium at the time of pregnancy recognition. Within a week of calving, lactating Holstein cows (n=12) were assigned to one of three supplements: hydrogenated plant oil (control), rumen-protected fish oil (PFO) or rumen-protected marine microalgae (PMA) high in docosahexanoic acid (DHA; C22:6, n-3). Diets were isolipidic and isonitrogenous, and were fed for four months. Circulating omega-3 PUFA concentrations were 5.96, 6.80, and 7.53% of total plasma fatty acids in control, PFO- and PMA-supplemented cows, respectively, after four months of supplementation. The PMA-supplemented cows had higher plasma DHA levels (0.72% ± 0.03, P<0.01) than PFO-supplemented cows (0.33% ± 0.02, P<0.01), which had higher levels than control animals (0.082% ± 0.005, P<0.01). Upon confirmation of pregnancy at day 17, uterine tissues were collected for analysis of relative expression and localization of progesterone receptor (PR), estrogen receptor-alpha (ERalpha), oxytocin receptor (OTR), peroxisome proliferator-activated receptor-delta (PPARdelta) and the enzyme prostaglandin H synthase-2 (PGHS-2). Cows fed either PFO or PMA showed stronger reactivity with PR antibodies in the deep glandular epithelium than those supplemented with the control (P≥0.05). Treatment differences in PR expression in other endometrial compartments were not significant, and western blotting failed to detect differences in overall PR expression (P>0.10). There was a tendency for stronger ERalpha antibody reactivity in the adluminal stroma in cows fed PMA (P<0.10), although western blotting of whole endometrial extracts indicated a trend for reduced ERalpha expression in PMA- versus PFOsupplemented animals (P<0.10). Immunohistochemistry did not indicate treatment effects on OTR, PPARdelta or PGHS-2 localization (P>0.10). However, relative protein levels of PGHS-2 were higher in cows supplemented with PFO or PMA in comparison to the control (P≥0.05), and PPARdelta expression was higher in PFO- than control- supplemented cows (P≥0.05). The results confirm the importance of source of omega-3 long chain PUFA in supplements for dairy cows. Marine microalgae are an alternative source of omega-3 PUFA that affect reproduction through different pathways than those of traditional fish-based supplements. (poster)

Improving ovine peri-conception diets by feeding an algal source of omega-3 fatty acids

The UK dairy industry currently suffers huge losses due to declining fertility. Although fertility in the sheep industry is good overall, the use of multiple ovulation and embryo transfer techniques would benefit from improved conception and embryo survival rates. Studies suggest that omega-3 supplementation may bring about a reduction in the secretion of prostaglandin F2α (PGF2α), which would favour the maintenance of the corpora lutea (CL) and hence, a successful pregnancy. Feeding fish meal to dairy cows has been found to improve pregnancy rates by 10% (Burke et al., 1997). Using sheep as a model, this study aimed to evaluate whether reproductive performance in ruminants is improved by feeding an algal source of omega-3 fatty acids, particularly docosahexaenoic acid (DHA, C22:6 n-3). The study was also structured to determine whether prostaglandin production is affected by supplementing diets with omega-3.

Maize Oil Can Replace Fish Oil in The Diet of Grouper Postlarvae (Epinephelus Coioides) Without Adversely Affecting Growth or Fatty Acid Composition

This experiment was conducted to evaluate the effects of dietary lipid sources on growth, survival and body composition of 40 day post hatch larval grouper, Epinephelus coioides. Fish were fed fish meal and protein hydrolysate based diets for 32 days with either 100% maize oil or 100% fish oil in triplicate from 40-day after hatching to slaughter size (fish weight: 0.32 g to 11 g). Final body wet weight (FBW: 11.8±0.7 and 11.1±0.1, respectively), weight gain (WG: 3556±251 and 3360±189, respectively), specific growth rate (SGR: 11.2±0.2 and 11.1±0.2, respectively) and survival rate (80±5 and 79±4, respectively) were not significantly affected by dietary lipid sources (P>0.05). The effect of different oil sources on the composition of tissues was significant only for dorsal muscle lipid. In dorsal muscle, lipid content was significantly higher in fish oil group. The fatty acids composition of the muscle lipids well reflected the fatty acids composition of the experimental diets. The growth performance showed that a balance is required between growth-promoting essential fatty acids (EFA) qualities of dietary n-3 highly unsaturated fatty acid (n-3 HUFA) and their potentially growth-inhibiting (pro-oxidant) qualities. Results indicated when EFA of the diet are sufficient for the development of postlarvae, there is no difference whether use fish or maize oil in the formulated diets, 2.87% n-3 HUFA is sufficient for grouper postlarvae development and more n-3 HUFA are not necessarily beneficial to fish performance.

The effect of preservation method of barley, maturity of grass silage, and type of protein supplement on sensory milk quality in organic farming

Three continuous production experiments and three short term cross over experiments were carried out in Northern Norway to investigate different feeding strategies for dairy cows in organic farming. This paper focuses on the effects on sensoric milk quality. Half of the 32 Norwegian red dairy cows in the production experiments were fed 40% (HC) concentrates (on energy basis per year) and the other half 10% (LC). Twelve cows (HC) participated in the short term cross over experiments. The experimental factors in the continuous production experiments were barley preservation method (P1), grass silage maturity (P2) and type of protein supplement (P3), and in the short term cross over experiments barley preservation method (C1), type of protein supplement (C2) and time for fishmeal feeding (C3). In all experiments the cows were offered grass silage ad libitum, restricted amounts of cereals and protein feeds, and mineral and vitamin supplements. The sensoric quality of milk was in general high. In the production experiments, milk from cows in HC had slightly higher quality than from cows in LC (significant in P2, p = 0.04). Neither the preservation method of barley (dried or ensiled with molasses), maturity of grass silage or type of protein supplement (fishmeal or peameal) influenced the sensoric milk quality significantly. Also in the cross over experiments no effect of the studied factors was found in milk flavour and odour. Early harvested grass silage gave significantly lower FFA contents than grass silage cut at normal time (P2) and FM gave significantly lower FFA concentrations than peameal (P3). These results indicate that organic farmers with different feeding regimes can produce milk of first class sensoric quality. Also the content of FFA has been low in all experiments (except C1). However, feeding regimes containing low levels of concentrates may reduce milk taste slightly.

Effects of Feeding Fish Meal and n-3 Fatty Acids on Milk Yield and Metabolic Responses in Early Lactating Dairy Cows

The study was designed to test the effects of feeding fish meal (FM) and specific n-3 fatty acids on milk yield and composition, dry matter intake, plasma concentrations of metabolic hormones and metabolites, and liver triglyceride accumulation in early lactating cows. From 5 to 50 d in milk (DIM), cows were fed diets that were isonitrogenous, isoenergetic, and isolipidic containing none (control), 1.25, 2.5, or 5% menhaden FM or 2.3% Ca salts of fish oil fatty acids (CaFOFA). Milk yield (48.2, 49.8, 48.6, 53.5, and 52.2±1.0kg/d, respectively) and dry matter intake (22.7, 22.8, 23.0, 23.8, and 24.7±0.5kg/d, respectively) differed among diets. Average daily plasma glucose concentration (53.4, 55.3, 51.1, 57.6, and 57.3±1.3mg/dL, respectively) was also affected by diet, and plasma insulin concentration was increased by 5% FM and 2.3% Ca-FOFA. At 25 and 50 DIM, blood was collected before feeding and hourly for 11h after feeding. Plasma glucose concentrations in cows during the day were similar among diets at 25 DIM, but differed at 50 DIM (54.6, 54.4, 52.4, 60.5, and 58.3±1.4mg/dL for 0, 1.25, 2.5, and 5% FM or 2.3% CaFOFA, respectively). Plasma insulin was increased in cows fed 5% FM and 2.3% CaFOFA at 25 DIM and was similar among diets at 50 DIM. Dietary treatments had no significant effect on milk composition, energy balance, or on daily plasma concentrations of nonesterified fatty acids, β-hydroxybutyrate, and urea. Plasma aspartate aminotransferase and hepatic triglyceride concentration in cows did not differ among diets at 21 DIM. Results from this experiment demonstrate that dietary supplementation with FM or n-3 polyunsaturated fatty acids in early lactating dairy cows significantly increased milk yield and DMI with no change in milk composition.

Effects of Feeding Fish Meal and n-3 Fatty Acids on Ovarian and Uterine Responses in Early Lactating Dairy Cows

The study was designed to test the effects of dietary supplementation with fish meal or specific n-3 fatty acids on ovarian activity and uterine responses in early lactating cows. From 5 to 50 d in milk (DIM), cows were fed diets that were isonitrogenous, isoenergetic, and isolipidic containing none (control), 1.25, 2.5, or 5% menhaden fish meal (FM) or 2.3% Ca salts of fish oil fatty acids (CaFOFA). Ovarian follicular dynamics were monitored along with plasma concentrations of estradiol and progesterone. Beginning at 23 DIM, cows were induced into a synchronized ovulatory cycle. On d 15 after ovulation (49 DIM), cows were injected with oxytocin and blood samples were collected to monitor uterine release of PGF2α (measured as 13, 14-dihydro-15-keto PGF2α; PGFM). Uterine endometrial biopsies were collected for fatty acid analysis and cyclooxygenase-2 (COX-2) protein measurement. Ovarian follicular activities as well as plasma estradiol and progesterone concentrations were similar across diets. Endometrial fatty acid composition of eicosapentaenoic acid (C20:5, n-3) and docosahexaenoic acid (C22:6, n-3) were increased as much as 3-fold by supplementation with fish meal and CaFOFA. Conjugated linoleic acid (C18:2 cis-9, trans-11) in the endometrium was also increased; conversely, arachidonic acid (C20:4, n-6) percentage was decreased by 5% FM. Plasma PGFM response to oxytocin injection was not different among diets and endometrial COX-2 protein abundance did not differ. Results from this experiment demonstrate that dietary supplementation with fish meal or n-3 fatty acids in early lactating dairy cows significantly increased uterine n-3 fatty acid concentrations, but had no apparent effect on endometrial COX-2 or PGF2α production in response to oxytocin challenge.

Fish Meal in Animal Feed and Human Exposure to Persistent Bioaccumulative and Toxic Substances

Persistent and bioaccumulative toxic substances (PBTSs) that end up in fish are health hazards and the object of fish-consumption advisories. Some of these substances are present as extraneous contaminants, e.g., man-made lipophilic pollutants such as organohalogen pollutants, and others such as monomethyl mercury can be considered naturally occurring. Omnivores (e.g., poultry and swine) and especially ruminants that are fed contaminated fish meal can pass monomethyl mercury and organohalogen pollutants to eggs, meat, and dairy products. Differences in fish meal PBTS profiles and farm animal (e.g., poultry, swine, cattle, and farmed fish) physiology modulate PBTSs in animal products. Fish-consumption advisories issued to protect human health do not extend to fish by-products fed to farmed animals. Animals (especially farmed fish) that are fed fish meal can bioconcentrate monomethyl mercury in protein matrices, and organohalogen pollutants can be passed on in the fat components of derived foods. Policies to decrease exposure to monomethyl mercury and organohalogen pollutants must consider farming practices that use fish by-products. A risk assessment of toxic contaminants in fish meal may indicate that food safety objectives must consider the human health impact of foods derived from animals fed contaminated meal.

Effect of replacing fish meal with soybean meal on growth, feed utilization and carcass composition of cuneate drum ( Nibea miichthioides)

The effect of replacing fish meal with soybean meal (SBM) in practical feeds for cuneate drum was evaluated in an 8-week net pen trial. The cuneate drum fingerlings (initial body weight 29.8 ± 1.3 g fish − 1 ) were fed six isonitrogenous and isocaloric feeds containing 39% digestible protein and 16 MJ kg − 1 digestible energy. The control feed was formulated to contain 40% herring meal, whereas in the other five feeds SBM was included at 11.3, 22.5, 33.8, 45.0 and 56.3% to replace 20, 40, 60, 80 or 100% of the fish meal. There were no significant differences in feed intake between fish fed the control feed and feeds in which SBM replaced 20 to 80% of the fish meal, but fish fed the fish meal free feed had higher feed intake than the other treatments. Weight gain linearly declined with the decrease of fish meal level. Final body weight (FBW) of fish fed the feeds in which SBM replaced 20% of the fish meal did not significantly differ from fish fed the control feed. Replacing 40 to 100% of the fish meal resulted in lower FBW and nitrogen retention efficiency (NRE), and higher feed conversion ratio (FCR) than those of fish fed the control feed. Fish fed the feeds in which SBM replaced 60 to 100% of the fish meal had lower condition factor and hepatosomatic index than those of fish fed the control feed. No significant differences in carcass protein content was found among the treatments, but fish fed the feeds in which SBM replaced 60 to 100% of the fish meal had higher moisture and lower lipid content in carcass than those of fish fed the control feed. Results of the present study appear to indicate that cuneate drum has a limited ability to utilize SBM as a protein source in practical feeds.

Effects of soybean meal based diet on growth performance, gut histopathology and intestinal microbiota of juvenile rainbow trout ( Oncorhynchus mykiss)

Effects of soybean meal (SBM) based diet on growth performance, histology of the intestinal epithelium and on the gut microbiota of juvenile rainbow trout ( Oncorhynchus mykiss) were investigated on two trials lasting for 8 weeks (Trial I) and 18 weeks (Trial II). The microbiological characterization was done both with conventional plating techniques, biochemical profiling and length heterogeneity analysis of PCR amplified 16S rDNA (LH-PCR). Typical histological changes were found after 18 weeks of SBM feeding (Trial II). Mean height of simple foldings were significantly higher within the group fed with fish meal (FM) based diet. These changes were not, however, reflected in the appearance, behavior and weight gain of the fish, although the feed conversion rate (FCR) was higher, compared to fish fed with the traditional FM feed. In both SBM and FM groups the counts of cultivable intestinal bacteria dropped within the first 4 weeks of feeding (Trial I). Subsequently, the bacterial numbers increased in the FM group, but not in the SBM group by the 8th week of the trial. The LH-PCR data suggested also that diet-related qualitative changes in the microbiota had occurred (Trial II). The main identified bacteria were mainly representatives of the genera Aeromonas, Sphingomonas and Chryseomonas, and among the lactic acid bacteria, Lactococcus and Lactobacillus. Future research will be directed to the identification and eventual elimination the SBM-associated factors involved in the inflammatory responses and unfavorable FCR, in particular by modifying the intestinal microbiota.

Characterisation of the microbiota associated with intestine of Atlantic cod ( Gadus morhua L.) : The effect of fish meal, standard soybean meal and a bioprocessed soybean meal

Populations of aerobic heterotrophic bacteria present in the gastrointestinal (GI) tract of healthy Atlantic cod ( Gadus morhua L.) fed three different diets, fish meal, standard or a bioprocessed soybean meal (BPSBM), were estimated using the dilution plate technique. A total of 944 isolates were characterised by biochemical and physiological properties and 425 isolates were identified further by sequencing the 16S rRNA genes. Our results showed that gut microbiota were affected by dietary manipulation. The GI tract of fish fed fish meal was dominated by Gram-positive bacteria of the genera Brochothrix and Carnobacterium. The Gram-negative bacteria Chryseobacterium spp. and Psychrobacter glacincola, and Gram-positive bacteria belonging to Carnobacterium, dominated in the digestive tract of fish fed soybean meal. In contrast to these results, genus Psychrobacter dominated in the GI tract when fish were fed BPSBM. Until recently, it was generally suggested that the gut microbiota of fish were less diverse than in homoeothermic animals. However, the present study identified several “new” bacterial species isolated from the alimentary tract of Atlantic cod. These “new” bacterial species are not normally isolated from the GI tract of fish. Based on our finding we suggest that the GI tract microbiota of fish might not be as simple as believed. Antagonistic activity of carnobacteria regarding inhibition of growth of two fish pathogens ( Aeromonas salmonicida ssp. salmonicida and Vibrio anguillarum) was observed. However, some difference in the antibacterial activity of Carnobacterium spp. was observed. Whether this antagonistic activity has any effect in challenge studies will be discussed, especially in relation to the finding that the digestive tract is one of the major infection routes in fish.

Effects of 3-thia fatty acids on expression of some lipid related genes in Atlantic salmon ( Salmo salar L.)

In this study, the effects of in vivo administration of 3-thia fatty acids (FAs) on lipid metabolism in muscle and liver of Atlantic salmon were investigated. Prior to analysis, the fish were kept in tanks supplied with 5 °C seawater for 20 weeks. The fish were fed fish meal and fish oil (FO)-based diets supplemented with either nothing (FO), or 0.3% and 0.6% of the 3-thia FAs dodecylthioacetic acid (DTA) and tetradecylthioacetic acid (TTA) respectively. The fish grew from an initial weight of 110 g to 220 g in the FO group and to approximately 160 g in the 3-thia FA groups. There was a significant higher mortality (66%) in fish fed 0.6% TTA than in fish fed the 0.3% DTA (15%) and FO diets (15%). None of the 3-thia FA diets affected the lipid content of the salmon muscle. The liver index, however, was significantly higher and the total liver fat content lower in the TTA group than in the FO group. Both DTA and TTA were incorporated into the lipid fraction of muscle and liver (0.4% to 0.9%). There were no major differences in the total FA composition of liver and muscle between the dietary groups; except for a small increase of n-3 polyunsaturated FAs (PUFAs) in liver of the DTA group. The mRNA expression of peroxisome proliferator-activated receptor (PPAR) α, apolipoprotein AI (ApoAI), apolipoprotein CII (ApoCII) and low-density lipoprotein receptor (LDL-R) was down-regulated in liver of the salmon fed 0.3% DTA. PPARα and ApoAI transcripts were also reduced in liver of salmon fed 0.6% TTA. Additionally, the hepatic lipoprotein lipase (LPL) mRNA level was 3.8 fold increased in TTA fish relative to the FO group. In muscle there were no significant changes in gene expression pattern of any of the genes investigated. This is the first report on the effects of 3-thia FAs on gene expression in Atlantic salmon.

Size-fractionated fish hydrolysate as feed ingredient for rainbow trout ( Oncorhynchus mykiss) fed high plant protein diets. II: Flesh quality, absorption, retention and fillet levels of taurine and anserine

In the work to find replacement for fish meal in feed for fish, the inclusion of plant protein sources at high dietary level is an important issue. The present experiment was carried out to reveal how different feed ingredients affected the eating quality of the grown up fish with focus on nitrogen compounds as amino acids, taurine and anserine. Six experimental diets were fed to rainbow trout in triplicates for 90 d. All diets were composed to be equal in protein, lipid, energy and lysine. Three levels of a mixture of plant sources (full fat soy, extracted soy, soy protein concentrate, corn gluten) constituting 57.2%, 73.9% and 90.6% of total dietary protein were used. A small amount of fish meal was added in 5 diets constituting 9.4% of total protein. A fish hydrolysate that was high in free amino acids, taurine and anserine was tested at 16% and 32% dietary inclusion of total protein. Two other diets contained the same level of protein from the same hydrolysate that was ultra filtrated to remove low molecular weight compounds. Digestibility of taurine and anserine was found to be close to 99% for all groups, except for the group containing high level of plant sources. The levels of taurine in whole trout and fillets decreased during the feed experiment, but were about the same for all groups at the end of the feeding experiment and independent of dietary levels. The level of anserine in fish and fillets was equal from start to end of the experiment and independent of dietary inclusion. Taurine and anserine therefore seem to be homeostatic regulated in trout and independent on dietary levels. Amino acid content in fish and fillet was also equal for all groups and independent of protein sources used in the diets. The chemical composition showed higher lipid and dry matter levels in fish and fillet in fish that grew the fastest. In conclusion, plant protein sources may be included in diets for trout at high levels without affecting the eating quality as evaluated by amino acids, taurine and anserine levels.

ＰＣＲ法を用いた飼料中の魚由来ＤＮＡの検出法の検討

The Japanese Government has prohibited the use of seafood protein, as well as mammalian protein, in ruminant feed. There is an official method to detect meat and bone meal, but no method is yet available to detect fishmeal in ruminant feed. We tried to develop a suitable method to detect fishmeal in ruminant feed, similar to the official method "PCR detection of animal-derived DNA in feed". Our previously reported primers (fishcon5 and fishcon3-1) showed low sensitivity, so we designed new primers based on a DNA sequence from yellowfin tuna mitchondrial DNA. Among the primers, FM5 and FM3 specifically detected fish DNA (sardine, yellowfin tuna, skipjack tuna, chub mackerel, Pacific saury, salmon, rainbow trout, Japanese anchovy, codfish and Japanese horse mackerel) from fish meat, and did not amplify DNA from animals and plants. The sensitivity for detection of the presence of fishmeal in ruminant feed was 0.01-0.001%.

Dietary protein source affects lipid metabolism in the European seabass ( Dicentrarchus labrax)

The study was undertaken to evaluate the effects of dietary protein sources on lipogenesis and fat deposition in a marine teleost, the European seabass ( Dicentrarchus labrax). Four isonitrogenous (crude protein (CP, N × 6.25), 44% DM) and isoenergetic (22–23 kJ/g DM) diets were formulated to contain one of the following as the major protein source: fish meal (FM), one of two soy protein concentrates (SPC) and corn gluten meal (CGM). Apparent digestibility coefficients of the diets and raw ingredients, as well as soluble nitrogen (ammonia and urea) and phosphorus excretion were measured. Growth rates of seabass fed plant protein-based diets were significantly lower than those fed fish meal based diet. The protein utilisation was strongly correlated to the dietary essential amino acids index. Measurements of N excretion (ammonia and urea nitrogen) confirmed these data. Daily fat gain at the whole body level ranged between 1.1 to 1.7 g/kg BW, with the highest values being recorded in fish fed the fish meal based diet. Levels of plasma triglycerides and cholesterol were lower in fish fed soy protein diets than in those fed the diet solely based on fish meal. Soy protein rich diets decreased the activities of selected hepatic lipogenic enzymes (glucose 6-phosphate dehydrogenase, malic enzyme, ATP-citrate lysase, acetylcoenzyme A carboxylase and fatty acid synthetase). Highest lipogenic enzyme activities where found in fish fed the fish meal diet, except for fatty acid synthetase which was increased in seabass fed the corn-gluten meal based diets. Overall data suggest that dietary protein sources affects fat deposition and the lipogenic potential in European seabass.

Dietary amino acids affect intestinal Clostridium perfringens populations in broiler chickens

An experiment was performed to examine the effect of protein source and dietary amino acid profile on intestinal levels of C. perfringens in broiler chickens. Broiler chickens (age = 14 d; n = 192) were fed diets containing 400 g kg-1 crude protein with fish meal, meat/bone meal, feather meal, corn gluten meal, soy protein concentrate, pea protein concentrate, or potato protein concentrate as the primary protein source along with a control diet containing 230 g kg-1 crude protein. The birds were orally inoculated daily, with 1 mL (~1.0 × 108 CFU mL-1) of an overnight culture of C. perfringens between 14 and 21 d of age, killed at 28 d of age and C. perfringens numbers in ileum and cecum were enumerated. Birds fed fish meal, meat/bone meal, feather meal and potato protein concentrate had significantly higher intestinal C. perfringens counts than the birds fed corn gluten meal, soy or pea protein concentrates or the control diet (P &lt; 0.05). The glycine content of the diets and ileal contents was significantly, positively correlated with C. perfringens numbers in ileum and cecum. Dietary glycine may be an important factor in the intestinal overgrowth of C. perfringens in broiler chickens. Key words: Clostridium perfringens, broiler chicken, amino acid, glycine, necrotic enteritis

Digestive enzyme response to supplemental ingredients in practical diets for juvenile freshwater crayfish Cherax quadricarinatus

A feeding trial was conducted to determine digestive enzyme activity in Cherax quadricarinatus in response to diet composition. Eight experimental diets, each containing one of squid, red crab, sardine (600 and 650 g kg )1 crude protein), sorghum, wheat meal, soy paste and the reference diet were evaluated over 30 days in terms of amylase, lipase, and protease activities in the hepatopancreas. The diet containing wheat meal produced the highest amylase activity. Lipase activity was not significantly different among treatments. Protease activity was higher in animals fed fish meal (60 g kg )1 protein), soy paste and reference diet. Results suggest that C. quadricarinatus can modify hepatopancreatic enzyme levels in response to different compounds in the diet and can digest a broad variety of ingredients, particularly starch.

Changes to feeding and dominance ranks following the introduction of novel feeds to African catfish

The effect of changing feeds on individual feed intake and feeding and dominance ranks in groups of African catfish Clarias gariepinus was investigated. Following feeding on a commercial feed groups (n = 3) of six African catfish were either fed fish meal (FM42) or maize gluten (MG35) based feeds for 5 days before being switched to the other feed for 5 days. Energy intake was significantly lower on FM42 than on MG35, dry matter intake and protein intake were significantly lower on FM42 than on commercial feed and this occurred whether FM42 was fed first or second. There were no significant differences between intake of MG35 and commercial feed. Thus, the action of changing the feed on its own did not affect feed intake since the decrease was shown to be feed‐specific to FM42. Six types of agonistic behaviours were identified and used to assign dominance rank. There were no correlations between dominance and feeding ranks. This was due to non‐linear hierarchies with one dominant fish in each group. Feeding ranks were more stable when feeding MG35 than FM42. Feeding rank stability (Kendall's coefficient of concordance) was significant in five out of six groups fed MG35 (compared with three out of six fed FM42). Feeding rank stability was higher in five out of the six groups when they were fed MG35 than when the same group was fed FM42. The experiment provided evidence that the introduction of a novel feed can, but does not necessarily, alter feed intake and that feed can influence the stability of feeding ranks.

Effects of 3-thia fatty acids on feed intake, growth, tissue fatty acid composition, β-oxidation and Na +,K +-ATPase activity in Atlantic salmon

Atlantic salmon ( Salmo salar) with an initial mass of 86 g were reared in 12 °C seawater for 8 weeks to a final average mass of 250 g. The fish were fed fish meal and fish oil-based diet supplemented with either 0%, 0.3% or 0.6% of tetradecylthioacetic acid (TTA), a 3-thia fatty acid. The specific growth rate (SGR) decreased with increasing dietary dose of TTA. The SGR of the group fed 0% of TTA (Control) was 1.8; that of the group fed 0.3% of TTA (TTA-L) was 1.7, and that of the group fed 0.6% of TTA (TTA-H) was 1.5. The mortality increased with increased dietary dose of TTA. The mitochondrial β-oxidation capacity in the liver of fish fed the TTA diets was 1.5 to 2 times higher than that of the Control fish. TTA supplementation caused substantial changes in the fatty acid compositions of the phospholipids (PL), triacylglycerols (TAG) and free fatty acids (FFA) of gills, heart and liver. The percentages of n−3 fatty acids, particularly 22:6 n−3, increased in fish fed diets containing TTA, while the percentage of the saturated FAs 14:0 and 16:0 in the PL fractions of the gills and heart decreased. The sum of monounsaturated FAs in the PL and TAG fractions from liver was significantly higher in fish fed diets containing TTA. TTA itself was primarily incorporated into PL. Two catabolic products of TTA (sulphoxides of TTA) were identified, and these products were particularly abundant in the kidney. TTA supplementation had no significant effect on the activity of the membrane-bound enzyme Na +,K +-ATPase.

Conjugated Linoleic Acid Increases in Milk When Cows Fed Fish Meal and Extruded Soybeans for an Extended Period of Time

The objective of this study was to determine the effect of feeding a conjugated linoleic acid (CLA) stimulating diet for an extended period of time on milk cis-9, trans-11 CLA and vaccenic acid (VA) concentrations. Twenty cows (16 Holstein and 4 Brown Swiss) were divided into 2 groups (n = 10 per treatment) for a 10-wk study. Cows in group 1 were fed a traditional corn-soybean-basal diet (control), while those in group 2 were fed a blend of 0.5% fish oil from fish meal and 2% soybean oil from extruded soybeans (FMESB) to achieve higher milk fat cis-9, trans-11 CLA and VA. Diets were formulated to contain 18% CP and were composed (dry matter basis) of 50% concentrate mix, 25% corn silage, and 25% alfalfa hay. Dry matter intake was not affected by diet. Milk production increased in cows fed the FMESB diet. Milk fat and milk protein percentages decreased with the FMESB diet; however, milk fat and protein yields were not affected by treatments. Milk fat cis-9, trans-11 CLA and VA concentration (g/100 of fatty acids) and yield (g/d) were 2.5-fold greater for cows fed the FMESB diet over the 10 wk of fat supplementation. For cows fed the FMESB diet, contents of milk fat cis-9, trans-11 CLA and VA gradually increased from the first week of fat supplementation, reached the highest concentrations in wk 3, then gradually decreased during wk 4 and 5 and then remained relatively constant until wk 10. The concentration of cis-9, trans-11 CLA and VA from the control diet was relatively constant over the 10 wk of fat supplementation. Concentrations of cis-9, trans-11 CLA and VA in milk fat can be increased within a week by feeding a blend of fish meal and extruded soybeans, and that increase remains relatively constant after wk 5 of fat supplementation.