Abstract Mannan oligosaccharides [Actigen; ACT (Alltech, Inc., Nicholasville, KY)] are refined low molecular weight carbohydrates obtained from the cell wall of a specific strain of Saccharomyces cerevisiae. Peer-reviewed studies with nursery swine has suggested that ACT can positively impact intestinal morphology and permeability, inhibit gut colonization of enteric pathogens, and improve the pattern of immune responses with and without viral challenges. To validate these findings, three commercial scale experiments involving a total of 10,634 nursery pigs [PIC 337 × 1050, initially 6.4 kg of body weight (BW)] were conducted. Pens of 36 to 50 mixed sex pigs were randomly assigned to 1 of 2 dietary treatments supplemented with 0 or 800 ppm of ACT, with a total of 112 replications per treatment. In all trials, pigs were fed a nursery program comprised of two phases. Phase 1 from d 0 to 21 (experimental diets) and Phase 2 from d 22-37, 22-43, and 22-44, in Exp. 1, 2, and 3, respectively (common diets). Phase 1 diets were corn-soybean meal based and contained 9% whey permeate, 5% rolled oats, and were formulated to contain 1.38% SID Lysine. Phase 2 diets were corn-soybean meal based and formulated to contain 1.30% SID Lysine. In all experiments, data were analyzed using the GLIMMIX procedure of SAS (Cary, NC) in a randomized complete block design with pen serving as the experimental unit and initial BW serving as blocking factor. Percentage mortality and full value pig were analyzed using a binomial distribution. No significant ACT × experiment interactions (P > 0.10) were observed in mortality or full value pig (Table 1). From d 0 to 21, there was no evidence for differences in average daily gain (ADG), average daily feed intake (ADFI), or gain to feed ratio (G:F; P > 0.10) between dietary treatments (data not showed). From d 0 to 44, mortality was reduced (P < 0.0002), and full value pigs increased (P < 0.0004) in pigs fed diets with 800 ppm compared with pigs fed diets without ACT supplementation. In conclusion, whereas pigs fed diets supplemented with 800 ppm ACT did not show growth performance advantages, these experiments suggest livability and full value pig improvements.
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