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Interaction between dietary protein and magnesium level in tilapia (Oreochromis niloticus)

1989; Elsevier BV; Volume: 76; Issue: 3-4 Linguagem: Inglês

10.1016/0044-8486(89)90081-1

1873-5622

Henryka Dąbrowska, K.‐H. Meyer‐Burgdorff, Katharina Günther,

Fish biology, ecology, and behavior

Tilapia (Oreochromis niloticus) of mean initial weight 10 g were given one of eight semipurified, casein-starch-based diets for 10 weeks. The experiment had a factorial design with two protein levels (24 and 44%) and four magnesium levels (approximately 0.07, 0.68, 1.0 and 3.2 g kg−1). Weight gains were lowest in those tilapia given Mg-deficient diets and increased with increasing Mg concentration to 1.0 g kg−1. The dietary Mg level of 3.2 g kg−1 led to severe growth retardation in the case of the low-protein fed group and only slight growth depression in fish on the high-protein diet. A dietary Mg content of 0.59–0.77 g kg−1 was adequate for optimum performance of this species. Plasma Mg concentration was depressed in fish fed an Mg-deficient diet, and the whole-body Mg content was significantly decreased in fish fed the low-protein diet. On the other hand, whole-body hypercalcinosis was evident in tilapia fed a Mg-deficient diet containing a high protein level. Tilapia fed the high-protein diet absorbed Mg from the rearing water (160% deposition as percent of intake) in comparison to fish fed the low protein diet (59% deposition). An increased level of dietary Mg (excluding the highest Mg level) resulted in decreased deposition of Mg and increased deposition of Ca, K and P in the tilapia body. On the low-protein diet, tilapia fed the highest Mg level showed a significant decrease in blood parameters, haematocrit and haemoglobin content, and sluggishness was observed in these fish.