A Forty-Nine Day Evaluation of Bio-Mos® Replacement of Roxarsone in a Commerically Based Broiler Feeding Program

A study was conducted to investigate the effects of roxarsone and Bio-Mos® on broiler production, gut morphology and bone strength. Three thousand and ten broilers were randomly assigned to 1 of 5 dietary corn-soybean meal based treatments: 1) negative control (NEG), basal diet; 2) positive control (POS; NEG + 27 ppm Bacitracin MD); 3) roxarsone (ROX; POS + 50 ppm of roxarsone); 4) Bio-Mos® (BIO; POS + 0.15 and 0.5% Bio-Mos® added during the starter and grower periods, respectively); 5) Bio-Mos®+All-Lac XCL (BIO+LAC; POS + 0.2, 0.1, and 0.05% Bio-Mos® during the starter, grower and finishing periods, respectively and 0.25g All-Lac XCL/bird sprayed at hatchery). On day 14, 7 of the 14 replicate pens/treatment were challenged with Eimeria maxima (3 x 104 oocysts/bird). Tibias were collected on day 28 and 49 to determine bone-breaking strength. Non-challenged birds had higher body weight gains (BWG) and lower feed conversion (FCR) from day 0 to 49 than challenged birds (P < 0.05). Jejunal crypt depth was increased in challenged broilers compared to non-challenged broilers at 28 days-of-age (P < 0.05). From day 0 to 35, ROX birds had lower BWG and FI than BIO and BIO+LAC birds (P < 0.05), while FCR was similar. Supplementing roxarsone resulted in reduced feed intake and BWG, but no significant differences were noted in FCR compared to feeding Bio-Mos®. ROX fed broilers had decreased ileal crypt depth compared to all other dietary treatments (P < 0.05). Muscle As concentration was lower than FDA allowable limits in broilers fed ROX without a withdrawal period at 28 days-of-age. Including roxarsone or Bio-Mos® did not generally improve production compared to broilers fed the negative diet.