109 Effects of post-weaning supplementation of immunomodulatory feed ingredient on body weight and cortisol levels in programmed fed beef heifers

The objective of this study was to determine the effects of an immunomodulatory feed ingredient during post-weaning on growth and cortisol levels of beef heifers. Commercial Angus heifers (n = 72) from two AI sires were blocked (n = 9) by sire and BW and then randomly assigned to one of two pens per block. Each pen (4 heifers/pen) per block was assigned to one of the treatments. Heifers were fed a commercial TMR twice daily from d 0 to 60 to gain 0.75 kg/day. The feed was top-dressed once a day with either 72g of Celmanax (CEL) or 72g of corn germ (CON) per pen. Body weight was collected on d -1, 0, 15, 30, 45, 60 and 61. Blood samples were collected on d 0, 15, 30, 45 and 60. Sixteen heifers (n = 8 CEL; n = 8 CON) were randomly selected for a corticotropin releasing hormone/ arginine vasopressin (CRH/AVP) challenge after the 60 d period. Two heifers per pen (n = 32) were randomly selected for a transportation challenge to evaluate stress response on d 61 or 62 of the study. Pen was the experimental unit and data was analyzed by ANOVA or repeated measures analysis as appropriate. Feed efficiency and BW gain was increased (P = 0.04) in CEL heifers compared to CON heifers. Serum cortisol concentrations were decreased (P < 0.01) in CEL heifers compared to CON heifers on d 30 to 60 post-weaning. Serum cortisol concentrations were decreased (P < 0.05) in CEL heifers compared to CON heifers during the CRH/AVP challenge from 60 to 150 minutes post infusion. Serum cortisol concentrations were decreased (P < 0.05) in CEL heifers compared to CON heifers throughout the transportation challenge. In summary, supplementation of Celmanax post-weaning increased BW gain and reduced cortisol concentrations in beef heifers.