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