Evaluation of mineral status in high dietary sulfur exposed or sulfur-induced polioencephalomalacia affected beef cattle

Abstract

Amat, S., McKinnon, J. J., Penner, G. B., Simko, E. and Hendrick, S. 2014. Evaluation of mineral status in high dietary sulfur exposed or sulfur-induced polioencephalomalacia affected beef cattle. Can. J. Anim. Sci. 94: 139–149. We examined the mineral status in beef heifers fed high S containing diets with differing forage-to-concentrate ratio (F:C), and in S-induced polioencephalomalacia (PEM) affected feedlot steers. A metabolism trial was conducted as a randomized complete block design using a 2×2 factorial treatment arrangement with main effects of dietary S and F:C using 16 ruminally cannulated heifers. The F:C was modified by altering the proportion of barley silage (4 vs. 51% dry matter), whereas, the S content was modified by using differing sources of wheat dried distillers’ grains with solubles (WDDGS) to achieve low and high S diets (LS=0.30 vs. HS=0.67%). Minerals including Cu, Co, Fe, Mg, Mn, Mo, Se and Zn were determined from rumen fluid, blood, brain tissue and urine. Urinary mineral excretion was also assed. During the course of the metabolic trial, an outbreak of S-induced PEM in a commercial feedlot was documented and brain minerals of these PEM steers (n=4) were contrasted with the experimental heifers fed HS diet. There were no interactions between dietary S concentration and F:C (P>0.05). Heifers fed HS diet had reduced (P<0.05) mineral intakes (except for Mo), ruminal Co, Fe and Mn, and serum Mg and Fe relative to those fed LS diet. Heifers fed low F:C diet had reduced (P<0.05) Cu, Fe, Mo and Se intakes, greater (P<0.05) ruminal Cu, Fe, Mn and Zn, and reduced (P<0.05) serum Cu and Se, and greater (P<0.05) serum Mg than heifers fed high F:C diet. Brain minerals were not affected (P>0.05) by F:C or dietary S. However, the PEM brains had reduced Cu (P=0.058), Fe (P=0.003) and Mo (P<0.001) relative to normal brains. Dietary S and F:C did alter the mineral status of the heifers, but no deficiencies or PEM were induced.