EFFECT OF ONION POWDER USED AS A FEED ADDITIVE ON GROWTH PERFORMANCE, FEED UTILIZATION AND WHOLE BODY OMPOSITION OF NILE TILAPIA FINGERLINGS CHALLENGED WITH PATHOGENIC AEROMONAS HYDROPHILA
Medhat E.A. Seden
Department of Fish Nutrition, Central Laboratory for Aquaculture, Research Abbassa, Egypt.
|Received 7/ 11/ 2013||
Accepted 17/ 12/ 2013
A 15-week experiment was conducted to evaluate the effect of onion powder (OP) on growth performance, feed utilization, and body composition of Nile tilapia, Oreochromis niloticus and its challenge against pathogenic Aeromonas hydrophila. All diets were iso-nitrogenous (35% crud protein), iso-lipidic (8.11%) and iso-caloric (4.63 kcal/g diet). OP was added to the diets at a rate of 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5%. Eighteen glass aquaria were stoked with 20 fish (0.82 g) per each in triplicates for each treatment. Fish were fed at feeding rate of 8% of fish body weight for the first forty five days then reduced to 5% for the second thirty days and finally reduced to 3% for the rest of the study. After the feeding trial, fish of each treatment were challenged with pathogenic A. hydrophila by intraperitoneal injection (I / P) for 10 days. The results showed that no significant difference was observed in fish survival among the different treatments and its range was 98.33- 91.65%. The maximum growth was obtained when fish fed on a diet contained 0.5% OP, while the lowest growth was obtained at the control group. The best feed conversion ratio (FCR), feed efficiency ratio (FER), protein efficiency ratio (PER), apparent protein utilization (APU) and energy utilization (EU) were obtained at 0.5% OP diet, while the lowest values were obtained at the control group. No fish mortalities were observed in fish fed on diets containing different OP levels and challenged against A. hydrophilla, while it was found to be 90% with the control group. Adding OP to fish diet at 0.5% reduced the feed cost by 26.47%. This study clearly showed that the OP could be added to practical fish diet at 0.5% to improve growth performance, feed utilization and fish immunity. Moreover it can reduce the feed cost.
Key words: Onion powder, Nile tilapia, growth performance, feed utilization, Aeromonas hydrophila-challenge.