Three experiments were conducted using crossbred weanling pigs (n=462) to determine the effect of yeast culture (YC) additions to starter diets containing dried whey or a fiber source on performance and nutrient digestibility. An 18% CP corn-soybean meal basal diet was used in all experiments. In Exp. I (n=192), YC (O or .75%) was used in diets with dried whey (0 or 15%) in two 5-wk trials (1 and 2). In Exp. II (n=174), YC (0 or .75%) was used in diets containing no added fiber, 8% soybean hulls (SH), or 8% peanut hulls (PH) in two 5-wk trials (3 and 4). Fifty-four of the pigs in Trial 4 were continued on test for three additional weeks in a grower phase. In Exp. II (n=96), YC (0 or .75%) was used in diets containing three levels of PH (0, 8, and 16%) in one 6-wk trial. In Exp. II, .05% chromic oxide was added to all six diets, and six grab samples were taken (twice daily every other day) during wk 4 and 6 for determination of the digestibility of DM, N, P, and fibrous components using the indirect method. Pigs in all experiments had ad libitum access to feed and water, and body weight and feed consumption were measured weekly.

Results from all experiments showed that there was no overall effect of treatments on ADFI. In Exp. I, there was no significant overall effect of YC on ADG or G:F in either trial. In Trial 2 of Exp. I, whey depressed overall ADG (P < .10) and G:F (P < .005). In the nursery phases of Exp. I, there were no significant dietary treatment effects on ADG. Gain to feed ratios tended to be increased (P < .10) by YC additions, but only in diets which also contained fiber. In the grower phase of Trial 4 (Exp. II), fiber additions depressed ADG (P < .005), whereas YC additions improved ADG (P < .01), particularly in pigs fed diets which also contained SH (P < .05). In Exp. III, pigs fed diets containing YC and 8% PH had an overall ADG similar to controls, whereas pigs fed diets containing YC alone or both YC and 16% PH had a lower overall ADG than control pigs (P < .10). Overall G:F ratios were decreased by PH inclusion (P < .01) and by supplemental YC (P < .05). Apparent digestibilities were not influenced by the inclusion of YC. The addition of PH linearly decreased the digestibilities of DM (P < .001), N (P< .05), NDF (P < .001), and ADF (P < .05), and increased the absorption of P (P < .05).

These results suggest that YC additions had no effect on ADG or ADFI, variable effects on G:F, and no effect on digestibilities of DM, N, NDF, or ADF, or the apparent absorption of P. Fiber additions, particularly PH at the 16% level, appear to depress ADG and G:F, and the digestibilities of DM, N, NDF, and ADF, but increase apparent absorption of phosphorus.