Triploid Atlantic salmon Salmo salar have a higher dietary phosphorus requirement for bone mineralization during early development

Abstract

The effect of a dietary phosphorus regime in freshwater on vertebra bone mineralization was assessed in diploid and triploid Atlantic salmon, Salmo salar. Fish were fed either a low phosphorus (LP) diet containing 10.5 g kg −1 total phosphorus or a normal phosphorus (NP) diet containing 17.4 g kg −1 total phosphorus from 3 to 65 g (day 126) in body weight. Two further groups were fed the NP diet from 3 g in body weight, but were then switched to the LP diet after 38 (10 g in body weight) or 77 (30 g in body weight) days. Growth, vertebral ash content (% ash) and radiologically detectable vertebra pathologies were assessed. Triploids were initially smaller than diploids, and again on day 77, but there was no ploidy effect on days 38 or 126. Vertebral ash content increased with increasing body size and those fish fed the NP diet had higher vertebral ash content than those groups fed the LP diet during the intervening time period, but this diet effect became less apparent as fish grew, with all groups having relatively equal vertebral ash content at termination. In general, triploids had lower vertebral ash content than diploids on day 38 and this was most evident in the group fed the LP diet. On day 77, those triploids fed the LP diet during the intervening time period had lower vertebral ash content than diploids. At termination on day 126, the triploids had the same vertebral ash content as diploids, irrespective of diet. There was a ploidy × diet interaction on vertebral deformities, with triploids having higher prevalences of fish with ≥1 deformed vertebra in all dietary groups except continuous NP. In conclusion, between days 0 and 77 (3-30 g body size), triploids required more dietary phosphorus than diploids in order to maintain similar vertebral ash content. A possible link between phosphorus feeding history and phosphorus demand is also discussed.

A temperature shift during embryogenesis impacts prevalence of deformity in diploid and triploid Atlantic salmon (Salmo salarL.)

“…Due to the incubation temperature differences and subsequent impact on developmental speed, the number of feeding days (d) from first feeding until the end of the trial differed between treatments (6, 364 d; 8, 386 d; 11, 395 d). Diploids were fed a standard commercial diet (BioMar INICIO Plus, 4.9 g/kg available P) and triploids were fed a triploid‐specific diet (BioMar INICIO Tri‐X, 7.7 g/kg available P), with the only difference in the formulation being P supplementation in Tri‐X, and thus in accordance with previously published triploid‐specific P requirements (Fjelldal et al., 2015; Sambraus et al., 2020; Smedley et al., 2018) and the manufacturer's guidelines (BioMar, UK).…”

“…In recent years, both vertebral and jaw deformity results in triploid trials have sparked investigation into nutritional requirements and triploid‐specific diets have been trialled with supplementation of minerals, in particular P (Burke et al., 2010; Fjelldal et al., 2015; Sambraus et al., 2020; Smedley et al., 2016, 2018; Taylor et al., 2015). In the present trial, all triploids were fed a high P diet, in accordance with previously published triploid‐specific P requirements (Fjelldal et al., 2015; Sambraus et al., 2020; Smedley et al., 2018). However, LJD was still observed in the higher temperature treatments, suggesting that lower incubation temperature during embryogenesis had a greater effect on favourable jawbone development than diet.…”

“…Triploidy in salmon refers to the extra set of chromosomes as a result of retention of the second polar body during meiosis, which, in turn, renders the fish sterile. It has been reported that triploids can be initially smaller than diploid siblings but have increased growth potential in later life (Benfey, 2016; Sambraus et al., 2020; Smedley et al., 2018; Taylor et al., 2011). This may be a result of a higher occurrence of hyperplasia in muscle fibres.…”

“…In order to support skeletal reinforcement for this enhanced growth, it is likely that triploids have higher nutritional requirements. Such results have elicited investigations into comparative nutritional requirements between ploidies (Burke et al., 2010; Clarkson et al., 2017; Fjelldal et al., 2015; Sambraus et al., 2020; Sambruas et al., 2017; Smedley et al., 2016, 2018; Taylor et al., 2015, 2019; Vera et al., 2017, 2019). Supplementation of nutrients and the development of triploid‐specific diets are certainly reducing prevalence of deformities; however, while dietary approaches have been effective in reducing the occurrence of malformation in triploids, pathologies such as lower jaw deformity (LJD) and some vertebral anomalies remain.…”

Digestive tract morphology and enzyme activities of juvenile diploid and triploid Atlantic salmon (Salmo salar) fed fishmeal-based diets with or without fish protein hydrolysates

“…Information about the nutritional requirements of triploids is incomplete, but it is known that supplementation of feeds with histidine and phosphorus may reduce the incidence and severity of eye cataracts and skeletal anomalies, respectively [15][16][17][18]. In particular, triploid salmon require more dietary phosphorus than diploids during early development to achieve comparable bone mineralization [19]. Also, there are indications that triploid salmon parr may have different micronutrient requirements and metabolic responses to dietary supplementation than their diploid counterparts when fed low levels of marine ingredients [20,21].…”