JZS (2018) Special Issue, 2 nd Int. Conference of Agricultural Sciences 613 Impact of high dietary carbohydrates on feed evacuation of common carp (Cyprinus carpio L.) Rabar Mahmoud Rasheed 1 & Nadir Abed Salman 2 1College of Agricultural Sciences, Sulaimani University, Bakrajo Street, Sulaimaniyah-Iraq 2Mazaya University College, Baladiat Street, Dhi Qar-Iraq Email: ndrslmn1@gmail.com Article info Abstract Original: 30/12/2017 Revised: 01/02/2018 Accepted: 10/02/2018 Published online: A total of 120 young common carp (Cyprinus carpio L.) ranging in weight from 25 g to 39 g were used to study the effect of feeding high carbohydrate diets on feed evacuation. Fish were fed at the rate of 3% body weight on three rations, standard ration SR (37%), and medium carbohydrate ration MCR (42%) and high carbohydrate ration HCR (53%) for 70 days in oval plastic tanks using 4 replicates for each treatment. Pellets enriched with 2% iron powder as a marker were used for additional 21 days for X-ray tracing. Pre-prandial starvation for one day was adopted before feeding the experimental diets and X–raying the fish at six intervals (1, 4, 8, 12, 24 and 48 h) after feeding to estimate the evacuation rate and time. Results showed that high carbohydrate ration was evacuated faster than MCR and SR ration. After 24 hours of feeding, 91 % of the HCR ration was evacuated compared with 84 and 79 % in both SR and MCR ration. Differences between HCR and the other two rations were significant (P<0.05).The rate of evacuating HCR ration ranged between 6.7 -7.6 % per hour compared with 5.5 -6.3% per hour for MCR and 5.7-7 % per hour for SR ration. The theoretical evacuation time of HCR reached 26 h. compared with 30-31 h for the MCR and SR rations respectively. The results were discussed in term of the role of inert and indigestible fibrous materials which can accelerate the passage of food in fish alimentary canal. The validity of the radiographic method for estimating the rate of evacuation in omnivores carp was also evaluated. Key Words: High carbohydrate Feed evacuation Common carp Introduction Production in both wild and cultivated fish populations are largely depends on food consumption and the way in which food is utilized within the body. Important aspects of trophic dynamics of fish include appetite, meal size and frequency, rate of gastric evacuation and assimilation efficiency and many other methods have been devised to study these parameters [1]. The development of optimum feeding schedule and gastric evacuation time for cultured fish include variables like temperature, season, body size, gut capacity, and metabolic rate. The rate of gastrointestinal evacuation is one of the major determinants of feeding rate [2]. Many factors such as temperature, meal size, fish size, dietary composition and feeding frequency will influence gastrointestinal evacuation [3]. One of the popular methods is to use the X- radiographic techniques to observe and describe the movement of food items in the alimentary tracts of fish after feeding [4] and [5]. It has been extensively reported that return of appetite is probably controlled by the stomach evacuation rate in teleostean fish species [6]. It was demonstrated by Tekinay and Guner, (2001) [7] that the appetite was more dependent on the bulk of the food rather than the dietary composition (energy Journal homepage www.jzs.univsul.edu.iq Journal of Zankoy Sulaimani Part-A- (Pure and Applied Sciences)