NIVEL DE PROTEÍNA, FIBRA Y CULTIVO DE LEVADURA Saccharomyces cerevisiae EN DIETAS A BASE DE TRIGO PARA CERDOS LEVELS OF PROTEIN, FIBER, AND YEAST Saccharomyces cerevisiae IN WHEAT-BASED DIETS FOR PIGS

The reduction in protein content and inclusion of wheat bran in the diet improves the amino-acids (AA) profile, but increases the fiber content. To this respect, yeasts can increase the digestion of fiber. Three experiments were carried out to evaluate the effect of yeast culture (YC) on diets with a standard (SCPD) or low level of crude protein (LCPD), with or without free AA, for growing-finishing pigs (Landrace- Hampshire-Duroc). In the three experiments the design was randomized complete blocks and data were analyzed with GLM procedure of SAS. In experiment 1, 28 growing pigs (25.2±4.7 kg) were used and there was a factorial arrangement 2 (CP, 11.0 and 18.8 %) × 2 (YC, 0 and 0.75 %) of treatments. The YC did not change (p>0.33) the productive response; the CP level did not influence weight gain (ADG) nor feed intake (FI; p>0.14), but the conversion (CA) was better (p=0.01) with SCPD. Experiment 2 was conducted with 40 finishing pigs (60.2 ±8.3 kg) and the treatments (T) were: T1) base diet, wheat-soybean-wheat-bran meal; T2) T1 + 0.75 % of YC; T3) T1 + 1.5 % of YC; T4) control diet wheat-soybean meal; and T5) diet low in CP + free AA. The YC did not change the performance nor the characteristics of the carcass; when it was compared with the LCPD, the area of the longissimus dorsi muscle (p=0.08) and the back fat (p=0.02) were better in pigs fed diets with YC CL, but yield (p=0.02), ADG (p=0.04) and FI (p=0.05) were higher in the LCPD. Experiment 3 was conducted with 32 finishing pigs (67.1±10.3 kg); and there was a factorial arrangement 2 (PC, 13.0 and 16.0%) × 2 (YC, 0 and 0.75 %) of treatments. The YC (p>0.70) and the CP level (p ³0.43) did not affect the response of the pigs. It can be concluded that the inclusion of YC in wheat-based diets does not influence the productive response of growing to finishing pigs.