Researchers, Veterinarians

Two 49-d winter pen trials using straight-run Ross × Ross broiler chickens at 0.667 ft2/bird (0.062 m2/bird) were conducted on new litter to compare the efficacy of commercial mannan oligosaccharide (MOS) as an alternative growth promoter to bacitracin methylene disalicylate (BMD) followed by virginiamycin (VM). Feed phases were 0 to 21, 21 to 42, and 42 to 49 d. In experiment 1, treatment effects were nonsignificant at 21 d. At 49 d, BMD (55, 55, or 27.5 ppm) or MOS (1,000, 500, or 500 ppm) significantly (P < 0.05) improved body weight and feed conversion ratio and increased feed expense per bird and net income (live value minus feed expense) per bird, without affecting mortality, compared with the unsupplemented negative control (nCON). In experiment 2, there were 6 dietary treatments: 1) nCON; 2) BMD (27.5, 55 ppm), VM (11 ppm); 3) MOS (1,000 ppm), BMD (55 ppm), VM (11 ppm); 4) BMD (27.5, 55 ppm), MOS (500 ppm)