226 Influence of trace mineral source on digestion, ruminal volatile fatty acid and soluble mineral on steers fed a dairy type diet balanced to meet requirements for a high producing lactating dairy cow

Abstract Twelve Angus steers (BW 530.9 ± 22.7kg) fitted with ruminal cannulae were used to determine the impact of trace mineral source on digestibility, ruminal VFA, and soluble concentrations of Cu, Zn, and Mn. Steers were fed a dairy type diet balanced to meet requirements for a high producing lactating dairy cow (DM basis: 16.8% CP, 29.2 Mcal NEm, 30.3 Mcal NEl, 33.6% NDF) for 21 d. Treatments consisted of 10 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either sulfate (STM), hydroxy (HTM; IntelliBond) or organic (ORG; metal specific amino acid complexes) sources (n=4 steers/treatment). Following a 21-d adaptation period, total fecal output was collected for 5 d. On d 6, rumen fluid was collected at 0, 2, and 4 h post feeding and analyzed for VFA. Steers were then fed the same diet without supplemental Cu, Zn, or Mn for 14 d. On d 15 steers received a pulse dose (cannulae) of 100 mg Cu, 400 mg Mn, and 60 mg Zn from either STM, HTM, or ORG. Ruminal samples were obtained at 2-h intervals starting at -4 and ending at 24 h post dosing and analyzed for soluble Cu, Mn, and Zn. Digestibility of NDF and ADF were lesser (P < 0.05) in STM vs. HTM and ORG supplemented steers. Steers receiving HTM and ORG had greater (P < 0.05) total VFA concentrations than STM supplemented steers at 2 and 4h post feeding. Ruminal soluble Cu and Zn concentrations were greater (P < 0.001) post dosing in STM and ORG supplemented steers at 2, 4, and 6 h for Cu and 4, 6, 8, 10 and 12 h for Zn when compared to HTM supplemented steers. Results indicate that ruminal solubility of Cu and Zn differs between STM, HTM and ORG sources and trace mineral source impacts fiber digestion and ruminal VFA concentrations.