Prenatal and postweaning dietary copper effects on cellular and humoral immunity in calves

Abstract

Calves born to Simmental cows fed one of four diets containing 0 (0-PN), 20 (20-PN), 40, (40-PN), or 80 (80-PN) ppm supplemental Cu during the last third of gestation were subsequently stratified by liver Cu at weaning (avg. = 24 [] 16 ppm DM) and assigned to one of three postulating Cu diets (0, 10 or 40 ppm supplemental Cu as a 1:1 mix of CuSO₄ and Availa Cu®) which were individually fed for 75 d. At day 42 calves were transported 760 km and inoculated with 1.68 x 10⁸ TCID₅₀ units of IBR on day 47. Liver biopsies and blood samples were obtained on days 0, 14, 28, 42, and 75. Cellular immunity was assessed on days 14, 28, 42, and 54 by measuring skin-swelling responses to intradermal injections of PHA. To determine humoral immunity SN antibody titers for IBR, BVD, BRSV and PI₃ following MLV vaccination on days 14 and 28, and IgG response to ovalbumin immunizations on days 47 and 61 were measured. Liver Cu surpassed the 100 ppm adequacy threshold by day 14 in 40-PW calves (156.5[]13 ppm DM) and day 28 in 10-PW calves (109.4 [] 13 ppm DM) while 0-PW calves remained Cu-deficient through day 42 (63.7 [] 13 ppm DM). Although PN x PW Cu interactions were significant on skin-swelling responses on days 14, 28, and 54, calves fed 10- and 40-PW diets had higher (P < .05) skin-swelling responses than 0-PW calves on days 28, 42, and 54. Skin-swelling responses were highest (P < .05) for 40-PN calves compared to 0-, 20-, and 80-PN calves on days 28, 42, and 54 despite minimal differences in liver Cu concentration. Humoral immune responses were not affected prior to stress by PW Cu, but increased (P < .05) after stress in 40-PW calves. Rectal temperature and DMI following stress were affected by a PW Cu x sex interaction (P < .01). These data suggest that PW supplemental Cu improves cellular immune responses before and after stress and humoral immune responses after stress. Moreover, PN Cu supplementation continued to affect cell-mediated immune responses of postulating calves despite minimal differences in liver Cu concentration.