Influence of Dietary Calcium, Phosphorus, Zinc and Sodium Phytate Level on Cataract Incidence, Growth and Histopathology in Juvenile Chinook Salmon (Oncorhynchus tshawytscha)

Abstract

To determine the influence of wide variations in dietary levels of calcium, zinc and phytic acid (as sodium phytate) on growth and cataract incidence, juvenile chinook salmon held at 10-11 degrees C were fed daily to satiation for 105 d one of nine purified diets containing one of three levels (grams/kilogram) of calcium (averaged 4.8, 17.7, 50.2), zinc (averaged 0.05, 0.15, 0.39) and phytic acid (1.62, 6.46, 25.8). Diets were formulated to have a calcium-phosphorus ratio of close to unity when considering phosphorus sources other than sodium phytate. High dietary phytic acid concentration (25.8 g/kg) depressed chinook salmon growth, food and protein conversion [protein efficiency ratio (PER)] and thyroid function, increased mortality, promoted cataract formation (zinc at 0.05 g/kg) and induced anomalies in pyloric cecal structure. Calcium at 51 g/kg (or phosphorus) exacerbated the effects of high dietary phytate and low dietary zinc on cataract incidence. Moreover, high dietary levels of calcium (48-51 g/kg) coupled with phosphorus significantly impaired the growth and appetite of low phytic acid (1.62 g/kg) groups and led to nephrocalcinosis in low and high phytic acid groups. Plasma zinc levels were directly related to dietary zinc concentration and inversely related to dietary phytic acid level. Calcium (51 g/kg) and/or phosphorus reduced zinc bioavailability when the diet concurrently contained 0.05 g zinc and 25.8 g of phytic acid per kilogram. It is concluded that zinc is essential for normal eye development in juvenile chinook salmon. Further, zinc deficiency could not be induced in chinook salmon fed diets with high ratios of calcium (or phosphorus) to zinc alone. This required the simultaneous presence of a strong mineral (zinc)-binding agent.

Feeding aquaculture in an era of finite resources

“…Zinc deficiency affects growth and bone development, but more importantly, can cause cataracts (55). The problem is exacerbated in the presence of phytic acid, which is found in meals and concentrates made from grains and oilseeds (56). Thus, using high-ash fishmeal in conjunction with high levels of plant protein concentrates in aquafeeds is likely to cause zinc deficiency in farmed freshwater fish unless dietary zinc levels are increased by supplementation or steps are taken to mitigate phytic acid [e.g., phytase supplementation (17)].…”

Effect of dietary cottonseed meal on growth performance, physiological response, and gossypol accumulation in pre-adult grass carp, Ctenopharyngodon idellus

“…More than 70% of the phosphorus in seeds is contained in phytic acid, which is indigestible by fi sh (Jackson et al, 1996). , which reduces bioavailability of these nutrients to fi sh (Richardson et al, 1985;D'Mello et al, 1991).…”

Availability of Dietary Zinc Sources and Effects on Performance of Pacific White Shrimp <i>Litopenaeus vannamei</i>(Boone)

“…Phytic acid has a strong affinity for zinc and other divalent minerals which results in their being unavailable to aquatic and terrestrial animals (Cheryan, 1980;Davis et al, 1993;Davis and Gatlin, 1996;Richards et al, 2010). Phytic acid has been observed to depress growth and also lower the availability of macro minerals and trace minerals in fish and shrimp (Spinelli et al, 1983;Richardson et al, 1985;Civera and Guillaume, 1989;Paripatananont and Lovell, 1995a;Usmani and Jaffri, 2002;Portz and Liebert, 2003;Helland et al, 2006;Laining et al, 2010). In the Pacific white shrimp L. vannamei, addition of phytic acid to diets did not significantly depress growth but it affected hepatopancreas zinc concentrations (Davis et al, 1993).…”

“…There is limited information on the availability of organic or chelated trace minerals in shrimp fed either phytic acid-containing or phytic acid-free diets. The effect of phytic acid on mineral availability has however been well documented in fish (Spinelli et al, 1983;Richardson et al, 1985;Helland et al, 2006;Laining et al, 2010) but has been less studied in shrimp. Phytic acid did not adversely affect growth in Penaeus japonicus but depressed growth in L. vannamei (Civera and Guillaume, 1989).…”