The utilization of dehulled lupin as a partial replacement for ®sh meal was studied in diets of rainbow trout. Fish were fed diets with 0%, 10%, 20%, 30%, 40% and 50% of dehulled lupin, at a daily feeding rate of 2% body weight for 8 weeks at 15 T 0.5°C. Growth performance generally decreased with increasing dehulled lupin in the diet (R 2 = 0.81, P < 0.0001). However, there was no signi®cant difference between 0%, 10%, 20%, 30% and 40% dehulled lupin fed groups. Feed conversion ratio generally increased at higher inclusion levels of dehulled lupin (R 2 = 0.74, P < 0.002). The protein ef®ciency ratio, protein productive value, lipid ef®ciency ratio and lipid productive value were similar in all groups but the energy ef®ciency ratio was signi®cantly lower (P < 0.01) in the 50% dehulled lupin fed group. Different treatments showed similar digestive enzyme activity, villus height, pyloric caeca and hepato somatic indexes. None of the nonspeci®c immune responses, with the exception of total plasma protein and neutrophils, was affected by different inclusion level of lupin. Results show that dehulled lupin can be included at up to 40% of a rainbow trout diet without a signi®cant effect on growth performance or nutrient utilization. Rainbow trout utilize dehulled lupin protein as ef®ciently as ®sh meal protein but have a lower ability to utilize the energy content of dehulled lupin at higher inclusion levels.
Previous studies have demonstrated that beta-glucans stimulate Atlantic salmon, Salmo salar L., head kidney macrophages both in vitro and in vivo and increase protection against various pathogens. Based on our previous work that showed potent immunostimulatory CpG motif-containing oligodeoxynucleotides increased resistance to amoebic gill disease (AGD), the present study investigated the immunostimulatory effects of three commercial beta-glucan-containing feeds and their ability to increase resistance to AGD. All three commercial beta-glucans were able to stimulate the respiratory burst activity of Atlantic salmon head kidney macrophages in vitro, albeit at different times and concentrations. However, dietary incorporation of the beta-glucans was unable to stimulate the in vivo respiratory burst activity of head kidney macrophages, or serum lysozyme production, and did not increase resistance against AGD. However, this trial showed for the first time that a small subpopulation of Atlantic salmon subjected to a severe AGD infection was able to resist becoming heavily infected and furthermore survive the challenge.
This study investigated lysine utilization at marginal lysine intake (mg day−1) in Atlantic salmon (Salmo salar L) parr fed diets similar to those used in dose–response lysine requirement experiments. Duplicate tanks of salmon were fed Diet PL20.1 (20.1 g lysine kg−1 and 19.8 MJ DE kg−1) containing 54% of the lysine in the crystalline (free) form at four intake levels for 50 days. Feed intake levels were measured at 0.59, 0.85, 1.10 and 1.16 (satiation)%BW day−1. In addition, duplicate tanks of salmon were fed to satiation with Diets FML9.1 (9.1 g lysine kg−1) and FML20.7 (20.7 g lysine kg−1) in which lysine was derived almost entirely from fish meal. Feed intakes of FML9.1 (0.70%BW day−1) and FML20.7 (1.21%BW day−1) were significantly lower and higher (P < 0.001) than the satiation intake of the Diet PL20.1, respectively. Over all dietary treatments, lysine deposition was dependent on lysine intake (LI, mg day−1) as described by the equation: lysine deposition (mg day−1) = 0.708LI − 0.035 (r2 = 0.97, n = 12, P < 0.001). Addition of marginal lysine intakes from Atlantic salmon dose–response lysine requirement literature resulted in an equivalent relationship. The linear relationship suggests that lysine utilization remains constant at marginal lysine intake over different dietary formulations and life‐stages. Consequently, the lysine requirement (allowance) of Atlantic salmon would be more appropriately estimated by a factorial approach, assuming constant efficiency of lysine utilization and the addition of obligatory lysine loss (maintenance). Efficiency of lysine utilization and obligatory lysine loss was estimated to be 71% and 0.05 mg day−1 from the current experiment and 78% and 0.10 mg day−1 with the addition of the literature data. Based on the constant lysine utilization observed in this study, it is proposed there is a need to re‐evaluate lysine requirements expressed as a dietary concentration.
Triploid Atlantic salmon populations are associated with higher prevalence of lower jaw skeletal anomalies affecting fish performance, welfare and value deleteriously. Anomalous lower jaw can be curved downward (LJD), shortened (SJ) or misaligned (MA). Two separate groups of triploid Atlantic salmon (~12 g) with either normal lower jaw (NOR) or SJ were visually assessed four times over three months for presence and concurrence of jaw anomalies (with severity classified) and opercular shortening to understand the relatedness of these anomalous developmental processes. The prevalence of jaw anomalies increased in both groups over time (NOR group - SJ, LJD and MA combined 0-24.5%; SJ group - LJD and MA combined 17-31%). SJ and LJD occurred both independently and concurrently whereas MA exclusively concurred with them. All three anomalies could be concurrent. Severity of both LJD and SJ increased in the SJ group only. Opercular shortening recovery was observed in both groups but at a slower rate in the SJ group. The SJ group specific growth rate (SGR) was significantly (P < 0.05) lower than the NOR group. This study demonstrated the concurrence of SJ, LJD and MA and showed possible deleterious consequences deriving from the conditions.
Development of a formulated pellet to replace ‘bait’ fish in farmed southern bluefin tuna (SBT), Thunnus maccoyii (Castelnau), feeds is in progress; however, inherent difficulties have been encountered in conducting large‐scale growth trials to evaluate experimental pellet quality. Consequently, alternative methods are being investigated to develop a suitable feed more rapidly. This work explored whether Atlantic salmon, Salmo salar L., could be used as a ‘surrogate’ species for nutrition research on SBT by screening experimental SBT feeds. Atlantic salmon (initial mean weight 161.4 g) were fed a commercial salmon feed (Com.Sal), a commercial northern bluefin tuna feed (Com.NBT), one of three experimental SBT feeds (CRC‐A, ‐B, ‐C) or dry pelleted pilchards for 42 days, at which time growth was assessed. In vivo and in vitro protein digestibility of the feeds was also evaluated. Weight gain of Atlantic salmon fed Com.Sal (99.8 g) and Com.NBT (93.5 g) were found to be significantly (P < 0.01) greater compared to those fed CRC‐C (68.2 g) and pilchard (56.1 g). Weight gain of salmon fed the CRC‐A (81.6 g) and CRC‐B (85.3 g) were also significantly different from the pilchard‐fed group, but not from CRC‐C. No significant correlation was found between salmon and SBT growth, although difficulties with conducting growth trials on SBT may have limited the ability to compare data. In vitro ingredient digestibilities, however, were used to predict whole feed digestibility, which was found to significantly correlate to weight gain in SBT. Although the use of digestibility techniques appears useful in formulating SBT feeds, the use of a ‘surrogate’ species such as Atlantic salmon to screen SBT feeds needs to be more fully investigated.
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