The Effects Of Calcium On Dietary Phosphorus Uptake By Hybrid African Catfish, Heteroclarias Fry

Abstract

The effect of calcium on dietary phosphorus uptake by the hybrid African catfish (Clarias gariepinus x Heterobranchus bidorsalis) fry was studied. Three hundred 1.25 ± 0.02 g hatchery-bred advanced fry were randomly stocked in 15 plastic baths (25 litre capacity) with fresh spring water (8.25 mg/l calcium) at 20 fish per bath. They were fed 38% crude protein diets three times daily for 42 days, at 5% body weight per day. The diets were formulated based on four inclusion levels (0.60, 0.80, 1.00, 1.20%) of phosphorus (P) applied as sodium phosphate and four inclusion levels (0.80, 1.20, 1.60, 2.00%) of calcium (Ca) applied as calcium carbonate. Results showed that fish fed the control diet demonstrated better response to P and Ca uptake than any of the other diets. The increasing P content of fish corresponded with the dietary increase and decrease of P and Ca respectively. There was no significant effect (P > 0.05) of the dietary Ca and P levels on the deposition of Ca and P in fish. The weekly mean weight gain increased with the dietary increase of P and Ca. The effect of the dietary increase of P and Ca levels on weight gain and feed conversion ratio (FCR) was also not significant (P > 0.05).

This study showed that dietary fortification with Ca and P probably suppressed weight gain and FCR in the hybrid catfish between 28 and 35 days of the experimental period, with improvement from 42 days. Secondly, the influence of the dietary fortification with Ca on P deposition in the fish was increased with the period of the experiment. This culminated in less deposition of P as the experimental days increased. The present result is indicative of the fact the Ca : P ratio was probably more critical at higher dietary P and Ca levels. Lastly, the value of the P content of fish was positively influenced by increasing level of dietary Ca up to 2.00% when reared in calcium–replete water.


Key words: phosphorus level, calcium level, catfish hybrid, phosphorus deposition, calcium-replete water

Ife Journal of Science Vol. 7(1) 2005: 71-77