Continuous light induces bone resorption and affects vertebral morphology in Atlantic salmon (Salmo salarL.) fed a phosphorous deficient diet

Abstract

This study investigated the combined effects of photoperiod and dietary P level on bone osteoclast and osteoblast activity, and morphology, as well as plasma vitamin D status in Atlantic salmon post‐smolts. The fish were reared under continuous light (LL) or 12 h light/dark (LD) per day, and fed diets with insufficient phosphorous (P) (4 g kg−1 available dietary P, LP) or sufficient P (8 g kg−1 available dietary P, HP) for 79 days in seawater. LL significantly increased plasma 25(OH)D3 level and bone tartrate resistant acid phosphatase (TRACP) activity, and decreased bone collagen XI α1 chain (col11a1) mRNA transcription. The LP diet significantly increased plasma 1,25(OH)2D3 level and bone alkaline phosphatase activity, but decreased bone TRACP activity and matrix metalloproteinase 13 (mmp13) mRNA transcription, and vertebral mineral content, stiffness and length/dorso‐ventral diameter (l/d) ratio. A significant interaction between light and P was only observed on the l/d ratio, and the LP‐LL group was the only group that developed vertebrae with a compressed morphology (significantly lowest l/d ratio). In practical terms, these results show that Atlantic salmon post‐smolts under continuous light may need P supplemented diets to support normal bone development.

Multigenic Delineation of Lower Jaw Deformity in Triploid Atlantic Salmon (Salmo salar L.)

“…Alp and mmp13 are responsible for bone formation and mineralisation and cartilage and bone resorption, respectively [73–79]. In Atlantic salmon, all these genes have been already shown to be differential expressed in poorly mineralised and deformed vertebrae relative to normal vertebrae [8, 80, 81]. The current study suggests their involvement in the development of a skeletal anomaly affecting the lower jaw in Atlantic salmon.…”

Vertebral deformities in farmed Atlantic salmon (Salmo salar L.) - etiology and pathology

“…(2010a) found that a group of postsmolts with a high mRNA expression level in vertebral bone of MMP‐13 (Matrix MetalloProteinase 13), which codes for a protein belonging to a family of proteins involved in the degradation of the extracellular matrix, developed a high percentage of fish with compressions later on. Furthermore, the development of vertebral deformities has been associated with an increase in TRACP enzyme activity in vertebral bone in Atlantic salmon (Fjelldal et al., 2012a), which shows that matrix degradation may play an important role in the pathogenesis of vertebral deformities in Atlantic salmon. Ytteborg et al.…”

“…Vitamin A, for example, has an antagonistic effect on vitamin D by reducing the concentration of calcitriol (Ørnsrud et al., 2009). Furthermore, the vitamin D system is affected by the photoperiod (Fjelldal et al., 2012a). Removal of the light sensitive pineal gland (Fjelldal et al., 2004), photoperiod manipulation (Fjelldal et al., 2005; Wargelius et al., 2009), and water temperature (growth rate) elevation (Grini et al., 2011) all affects vertebral bone mineralization in Atlantic salmon.…”

Utilization of acid hydrolysed phosphorous from herring bone by-products in feed for Atlantic salmon (Salmo salar) start-feeding fry

“…Thus, the transcription of this gene may as well be linked to the impaired ossification front in the arches, as described previously in this paper. It has already been shown that diets with low or suboptimal levels of P may change gene and protein activity in salmon reared under continuous light, like changed concentration of the active vitamin D hormone 1,25 OH 2 D 3 , a subsequent increase in ALP activity and reduction in TRACP activity in bone (Fjelldal et al, 2012a). In this study, no stimulation in bone ALP activity or plasma 1,25 OH 2 D 3 was observed in the low P group, despite severe morphological changes in the bone, consistent with inadequate dietary P. Salmon fry given diets containing 0.5, 0.7 and 1.4% soluble P from first feeding to 50 g showed a clear dose-response for these enzymes, with the highest ALP and low TRACP activity at low P intake (Fjelldal et al, 2012b).…”