Performance and nutrient digestibility in weanling pigs as influenced by yeast culture additions to starter diets containing dried whey or one of two fiber sources

Three experiments were conducted using crossbred weanling pigs (7.2 to 8.6 kg; 25 to 29 d of age) to determine the effect on performance and nutrient digestibility of .75% yeast culture (YC) additions to starter diets containing whey or one of two fiber sources. An 18% CP corn-soybean meal basal diet was used in all experiments. In Exp. 1 (n = 192), the addition of YC did not affect ADG, ADFI, or gain: feed ratios (G:F) of pigs fed diets without or with 15% dried whey in two 5-wk trials. In Exp. 2 (n = 174), ADG and ADFI were not affected by YC addition to diets containing no added fiber, 8% soybean hulls (SH), or 8% peanut hulls (PH) in two 5-wk trials. The addition of SH or PH did not affect ADG or ADFI; however, a YC X SH interaction (P < .05) and a YC X PH interaction (P < .10) for G:F indicated that the addition of SH or PH to the diet in the absence of YC reduced G:F, but in the presence of YC, G:F were maintained. In a 3-wk grower phase of one trial in Exp. 2 (n = 54), SH and PH additions decreased ADG (P < .005), whereas YC additions improved ADG (P < .01), particularly for pigs fed diets that also contained SH (P < .05). In Exp. 3 (n = 96), pigs fed diets containing YC and 8% PH had an overall ADG similar to that of controls, whereas pigs fed diets containing YC alone or diets containing both YC and 16% PH tended to have lower overall ADG than control pigs (P < .10). Gain:feed ratios were decreased by PH inclusion (P < .01) and by supplemental YC (P < .05). In Exp. 3, the addition of PH linearily decreased the apparent digestibilities of DM (P < .001), N (P < .02), NDF (P < .001), and ADG (P < .03) and increased the apparent absorption of P (P < .02), but coefficients were not influenced by YC inclusion. In summary, YC additions had no effect on ADG and ADFI, variable effects on G:F, and no effect on apparent digestibilities of DM, N, NDF, and ADF and the apparent absorption of P. The inclusion of PH linearly decreased G:F and digestibilities of DM, N, NDF, and ADF but increased apparent absorption of P.