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Abstract
SUMMARY
This study was carried out at the fish farm of the Faculty of Agriculture (Saba-Basha), Alexandria University. It was conducted to evaluate and determine the effect of different fertilizer applications (chemical fertilizer, agriculture by-products (compost) and organic fertilizer (fish reger fertilizer) in a combination with artificial feed on survival, fish growth performance, feed efficiency, water quality and total yield of Nile tilapia.
The first experiment was designed to study the effect of dietary protein level and chemical fertilizer on fish growth performance of Nile tilapia fry (1.3 g) in the winter season from October 2003 to March 2004. Fish were stocked at the rate of 25 fish/m3. Four treatments were used; two dietary protein levels 20 and 25% each with or without chemical fertilizers at the rate of 15 kg/ feddan/ wk of mono superphosphate (15.5 P2O5) and 19 kg/ feddan/ wk urea (46% N). Water temperature ranged between 12 and 26°C during the experimental period.
Results indicated that final body weight was significantly affected by fertilizer treatments (P < 0.05) but not affected by increasing protein level (P < 0.05). Highest final body weight 13.52 g was obtained with second treatment (20% dietary protein plus fertilizer).
Survival percentages obtained at the end of the experiment showed that there was a negative relationship between final body weight and survival percentages, third treatment (25% dietary protein without fertilizer) was the highest in survival percentage 63.1% while the lowest was 31.6% in the first treatment (20% dietary protein without fertilizer). With increasing dietary protein levels, survival percentages increased. Final density of fish in ponds had the same trend of survival percentage. It ranged between 15.7 fish/m3 at third treatment and 7.9 fish/m3 at first treatment.
Data showed that there were a positive effect between fertilizer and both of average daily gain and protein efficiency ratio. Feed conversion ratio (FCR) improved significantly with increasing dietary protein level and with fertilizer treatments. Body composition of Nile tilapia fry was not affected significantly by treatments (P < 0.05).
Water quality parameters showed that there was a positive relationship between either nitrogenous compounds or total phosphorus and fertilizer treatments.
The second experiment was carried out to evaluate the effect of several fertilization treatments in combination with supplemental feed contained 25% crude protein on fish production, feed efficiency, water quality and net return of Nile tilapia with initial body weight (21 g) stocked at the rate of 5 fish/m3 earthen ponds.
Four treatments were carried out in this experiment each in two replicates. The treatments were: first treatment, feed only as a control; second treatment, fish reger fertilizer at the rate of 266 kg/feddan /wk plus feed; third treatment, compost fertilizer at