EVALUATION OF THE YEAST “Saccharomyces cerevisiae” AS AN ADDITIVE TO TILAPIA, Oreo chromis niloticus, FEEDS

This experiment was conducted to determine the optimum level of adding




the yeast Saccharomyces cerevi$iae to tilapia feeds. Two types of feed were used ,




the first feed type contained fish meal and the second feed type contained a whole




plant ingredients. Four experimental diets were formulated for each type of feed. The




dried bakery yeast (DBY) was added to three of the experimental diets at levels of




0.1%, 0.2% or 0.3%. The fourth experimental diet did not contain the (DRY) and used




as a control diet. These experimental diets were fed to tilapia, Oreo chromis niloticus




fingerlings for a period of seven weeks. The results showed that growth performance




and feed utilization had improved at all addibon levers of (DBY). The addition of the




(OBY) at levels of 0.2% or 0.3% had showed no significant improvement rather than




this given the 0.1%. The addition of (DRY) to a whole plant diet had resulted in




growth rates that are significantly equivalent to that of a diet containing fish meal




without the addition of OBY. Therefore, ¡t could be recommended that the use of 0.1%




of DRY to tilapia diets would be of economic worthiness.




INTRODUCTION




With increasing consumer demand for fish and declining supply from




natural waters, the aquaculture industry has to compensate this shortage in




fish supply. As aquaculture technology has evolved, the push toward higher




yields and faster growth has evolved the replacement of natural foods with




prepared diets. This type of feeds should contain not only necessary nutrients




but also complementary additives to keep organisms healthy and to support




maximum growth. Growth promoters include hormones, antibiotic, lonophores




and some salts (NRC, 1993). However, the improper use of these growth




promoters may cause adverse effects to the animal and to the final consumer




and could also lead to resistance in pathogenic bacteria in the case of




antibiotic. (Fuller, 1992).




Consequently, fish nutritionists have tried to examine other materials




to be used as growth promoters in fish feeding. Recently, probiotics have




been used for supplementing diets ¡n many fish species. Common carp fed




on diets supplemented with yeast (S. cerevisiae) gained better growth




response compared with those fed on either antibiotics or bacteria (S.




faeciLim) (Noh et aI., 1994). Bogut et aI., (1998) reported that S. faecium has




a better probiotic additive for carp than yeast. A significant increase ¡n the




growth of cultured trout was observed when yeast isolated from the intestines




of wild trout was introduced into the digestive tracts of cultured trout (Vázquez




— Juárez et aI., 1993). Lara. Flores et aI., (2003) concluded that the addition




of 0.1°/o S. faecium, L. aceidophilus or S. cervisiae in tlapia fry diets improves




animal growth, and the yeast produced the best results. They also noted that