Evaluation of barley protein concentrate and fish protein concentrate, made from trimmings, as sustainable ingredients in Atlantic salmon (Salmo salar L.) feeds

Barley protein concentrate (BPC) was tested as a protein source in the diets of Atlantic salmon post-smolts. Fish were fed one of four experimental diets consisting of a fish meal/soya protein concentrate control (CT) along with two feeds supplemented with increasing levels of BPC replacing the more costly SPC. A fourth diet partially replaced FM in the high BPC diet with a liquid fish protein concentrate (FPC) made from fish trimmings. No significant differences were observed in terms of growth at the end of the 12-week feeding period, although the protein efficiency ratio (ggaing−1protein consumed) was significantly lower for the control compared to fish fed diets containing either BPC only or FPC and BPC. This suggests that diets containing BPC had a beneficial effect when compared to the control diet. Furthermore, the lack of any detriment to fish growth in diets containing BPC suggests there are no significant issues regarding any negative effects of potential antinutritional factors which can otherwise be the case with other plant origin products. The data presented in this study indicate that BPC and FPC are products which could be of benefit to salmon culture, and related species, in providing a valuable new raw material to the industry

Evaluation Of Sensitivity To Chemotherapeutants In Successive Generations Of Lepeoptheirus Salmonis From A Resistant Population

There are currently reports of reduced sensitivity to certain lice treatments in different parts of Scotland and world-wide, and research is on-going into the extent and mechanisms of resistance to different treatments (Denholm et al., 2002; Sevatdal & Horsberg, 2003; Sevatdal et al., 2005). In particular, increasing evidence of resistance of Lepeophtheirus salmonis to the chemotherapeutant emamectin benzoate (Lees et al., 2008; Espedal et al., 2010) poses a serious problem to commercial farms because there are few licensed and effective treatments available

Nutritional intakes of highly trained adolescent swimmers before, during, and after a national lockdown in the COVID-19 pandemic

Strict lockdown measures were introduced in response to the COVID-19 pandemic, which caused mass disruption to adolescent swimmers’ daily routines. To measure how lockdown impacted nutritional practices in this cohort, three-day photograph food diaries were analysed at three time points: before (January), during (April), and after (September) the first UK lockdown. Thirteen swimmers (aged 15 ± 1 years) from a high-performance swimming club submitted satisfactory food diaries at all time points. During lockdown, lower amounts of energy (45.3 ± 9.8 vs. 31.1 ± 7.7 kcal∙kg BM∙day-1, p0.05), despite fewer training hours being completed (15.0 ± 1.4 vs. 19.1 ± 2.2 h∙week-1, p<0.001). These findings highlight the ability of adolescent swimmers to alter their nutrition based on their changing training circumstances when receiving sport nutrition support. However, some individuals displayed signs of suboptimal nutrition during lockdown that were not corrected once training resumed. This warrants future research to develop interactive education workshops that maintain focus and motivation towards optimal nutrition practices in isolated periods away from training

Interactions between dietary docosahexaenoic acid and other long-chain polyunsaturated fatty acids on performance and fatty acid retention in post-smolt Atlantic salmon (Salmo salar)

A study with varying dietary inclusion levels (1, 5, 10, 15 and 20 g kg-1) of docosahexaenoic acid (DHA; 22:6n-3) was conducted with post-smolt (111 &plusmn; 2.6 g; mean &plusmn; S.) Atlantic salmon (Salmo salar) over a 9-week period. In addition to the series of DHA inclusion levels, the study included further diets that had DHA at 10 g kg-1 in combination with either eicosapentaenoic acid (EPA; 20:5n-3) or arachidonic acid (ARA; 20:4n-6), both also included at 10 g kg-1. An additional treatment with both EPA and DHA included at 5 g kg-1 (total of 10 g kg-1 long-chain polyunsaturated fatty acids, LC-PUFA) was also included. After a 9-week feeding period, fish were weighed, and carcass, blood and tissue samples collected. A minor improvement in growth was seen with increasing inclusion of DHA. However, the addition of EPA further improved growth response while addition of ARA had no effect on growth. As with most lipid studies, the fatty acid composition of the whole body lipids generally reflected that of the diets. However, there were notable exceptions to this, and these implicate some interactions among the different LC-PUFA in terms of the fatty acid bio- chemistry in this species. At very low inclusion levels, DHA retention was substantially higher (*250 %) than that at all other inclusion levels (31&ndash;58 %). The inclusion of EPA in the diet also had a positive effect on the retention efficiency of DHA. However, EPA retention was highly variable and at low DHA inclusion levels there was a net loss of EPA as this fatty acid was most likely elongated to produce DHA, consistent with increased DHA retention with addi- tional EPA in the diet. Retention of DPA (22:5n-3) was high at low levels of DHA, but diminished with increasing DHA inclusion, similar to that seen with DHA retention. The addition of EPA to the diet resulted in a substantial increase in the efficiency of DPA retention; the inclusion of ARA had the opposite effect. Retention of ARA was unaffected by DHA inclusion, but the addition of either EPA or ARA to the diet resulted in a substantial reduction in the efficiency of ARA retention. No effects of dietary treatment were noted on the retention of either linolenic (18:3n-3) or linoleic (18:2n-6) acids. When the total n-3 LC-PUFA content of the diet was the same but consisted of either DHA alone or as a combination of EPA plus DHA, the performance effects were similar

Triploid Atlantic salmon growth is negatively affected by communal ploidy rearing during seawater grow-out in tanks

Using sterile triploid salmon is of interest to fish farmers as a means to mitigate interbreeding between farmed and wild fish, prevent pre-harvest maturation and offer potential for faster growth. We investigated within the same experiment whether growth, deformity and cataract prevalence in diploid and triploid Atlantic salmon post-smolts (8 full-sib families) were influenced by isolated- or mixed-ploidy rearing during 12 months of sea water grow-out in tanks until harvest. Diploids attained significantly higher harvest weights than triploids in both treatments (+ 6.7% isolated, + 26.3% mixed). Triploid harvest weight was 29.6% lower under mixed ploidy rearing than their isolated triploid siblings. A similar effect was also observed in diploids (12% lower harvest weight). Family had a significant effect on harvest weight in both ploidy. However, family harvest weight in triploids showed a linear relationship between isolated and mixed rearing (r2 = 0.76), while a non-linear relationship was found between diploids reared in isolation or mixed populations (r2 = 0.88). Furthermore diploid family weight correlated positively with triploid weight in isolation (r2 = 0.65), but a non-significant relationship was observed under mixed rearing (r2 = 0.49). Diploids had a significantly higher condition (K) factor at harvest than triploids in both treatments, while triploid K factor was significantly reduced by mixed rearing with diploids. Triploids had a significantly higher incidence of cataract than diploids in both treatments (60.9-77.3% vs. 21.7-47.2%, severity &ge; 1). However, severity of cataract was greater in both triploids (2.43) and diploids (1.44) grown in isolation than those grown in a mixed ploidy population (triploid 2.17; diploid 1.09). Triploids had a significantly higher prevalence of visible deformity than diploids (18.1 vs. 7.2%), however, triploids grown in isolation had significantly higher prevalence than triploids under mixed rearing (30.4 vs. 5.8%). Collectively, the results provide clear evidence that triploids perform very differently when reared in the presence or absence of diploid conspecifics. Furthermore, observations of reduced deformity and cataract in the slower growing mixed populations support the hypothesis that such malformations are in part a function of higher growth rate. The results of this study also indicate that care should be taken when designing conventional common garden experiments to evaluate family performance between ploidy as interactions between ploidy may influence growth traits, although family effects appear to remain consistent

Hypoxia does not change responses to dietary omega-3 long-chain polyunsaturated fatty acids, but rather reduces dietary energy demand by Atlantic salmon

Over 116 days, Atlantic salmon postsmolts of 183 ± 5 g were fed diets with high or low levels of lipid (230 or 180 g/kg) with high or low levels of omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA; 14 or 7 g/kg). Fish were reared under hypoxic and normoxic conditions (6.7 or 8.0 mg/L), as an environmental stressor. Higher levels of lipid and n-3 in the diet increased final weight and weight gain, although no lipid x n-3 interaction was found across both environments. Hypoxia led to reduced growth, which can be explained by reduced feed intake, with no effects on FCR being observed. High lipid diets improved protein and energy retention in the fish carcass as well as improved the digestibility of lipid and LC-PUFA, including EPA and DHA. High n-3 diets also improved retention and digestibility of LC-PUFA, and transcriptomic analysis showed that the liver had reduced levels of expression of fatty acid synthesis genes, for example fads2d5 and elovl2 in those treatments. A clear relationship between performance and energy intake, independent of n-3 LC-PUFA intake, shows that energy demand under hypoxia was an over-riding feature of the nutritional responses in this study.submittedVersio

Hypoxia does not change responses to dietary omega-3 long-chain polyunsaturated fatty acids, but rather reduces dietary energy demand by Atlantic salmon

Over 116 days, Atlantic salmon postsmolts of 183 ± 5 g were fed diets with high or low levels of lipid (230 or 180 g/kg) with high or low levels of omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA; 14 or 7 g/kg). Fish were reared under hypoxic and normoxic conditions (6.7 or 8.0 mg/L), as an environmental stressor. Higher levels of lipid and n-3 in the diet increased final weight and weight gain, although no lipid x n-3 interaction was found across both environments. Hypoxia led to reduced growth, which can be explained by reduced feed intake, with no effects on FCR being observed. High lipid diets improved protein and energy retention in the fish carcass as well as improved the digestibility of lipid and LC-PUFA, including EPA and DHA. High n-3 diets also improved retention and digestibility of LC-PUFA, and transcriptomic analysis showed that the liver had reduced levels of expression of fatty acid synthesis genes, for example fads2d5 and elovl2 in those treatments. A clear relationship between performance and energy intake, independent of n-3 LC-PUFA intake, shows that energy demand under hypoxia was an over-riding feature of the nutritional responses in this study

Adult triploid Atlantic salmon (Salmo salar) have higher dietary histidine requirements to prevent cataract development in seawater

The study investigated cataract preventive effects of dietary histidine (His) supplementation in triploid Atlantic salmon during seawater grow-out. Groups of individually PIT tagged diploid (2N) and triploid (3N) postsmolts were fed one of two supplemented dietary histidine levels; low (L, 12.6 g kg-1 diet) or high (H, 17.4 g kg-1 diet) from March to September following their first sea winter. Low severity cataracts were detected in both ploidy prior to supplemented His diet application. Thereafter, 3N-L showed progression of cataract development in the second spring-summer period, while development was inhibited in 3N-H. Severity of cataract showed a strong family effect. A positive correlation between initial triploid seawater growth (weight and TGC) under increasing water temperature and cataract severity was identified as a major risk factor. The relationship was reversed at harvest, where triploids were on average 7.5% smaller than their diploid siblings. Lens N-acetyl-histidine content reflected dietary His inclusion level and cataract severity, although no significant differences in lens His content were evident between ploidy or dietary groups. Results indicate that triploid Atlantic salmon appear to have a higher dietary histidine requirement than diploids and that preventative measures can be taken to mitigate further cataract development

The time to peak blood bicarbonate (HCO 3 – ), pH, and the strong ion difference (SID) following sodium bicarbonate (NaHCO 3 ) ingestion in highly trained adolescent swimmers

The timing of sodium bicarbonate (NaHCO3) supplementation has been suggested to be most optimal when coincided with a personal time that bicarbonate (HCO3–) or pH peaks in the blood following ingestion. However, the ergogenic mechanisms supporting this ingestion strategy are strongly contested. It is therefore plausible that NaHCO3 may be ergogenic by causing beneficial shifts in the strong ion difference (SID), though the time course of this blood acid base balance variable is yet to be investigated. Twelve highly trained, adolescent swimmers (age: 15.9 ± 1.0 years, body mass: 65.3 ± 9.6 kg) consumed their typical pre-competition nutrition 1–3 hours before ingesting 0.3 g∙kg BM-1 NaHCO3 in gelatine capsules. Capillary blood samples were then taken during seated rest on nine occasions (0, 60, 75, 90, 105, 120, 135, 150, 165 min post-ingestion) to identify the time course changes in HCO3–, pH, and the SID. No significant differences were found in the time to peak of each blood measure (HCO3–: 130 ± 35 min, pH: 120 ± 38 min, SID: 98 ± 37 min; p = 0.08); however, a large effect size was calculated between time to peak HCO3– and the SID (g = 0.88). Considering that a difference between time to peak blood HCO3– and the SID was identified in adolescents, future research should compare the ergogenic effects of these two individualized NaHCO3 ingestion strategies compared to a traditional, standardized approach