Trace mineral source impacts rumen trace mineral distribution and fiber digestion in steers fed a low-quality forage-based diet
Date
2020
Authors
Guimaraes, Octavio, author
Engle, Terry, advisor
Geornaras, Ifigenia, committee member
Holt, Timothy, committee member
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Abstract
Twelve Angus steers (BW 452.8 ± 21.8 kg) fitted with ruminal cannulae were used to determine the impact of trace mineral (TM) source on neutral detergent fiber (NDF) digestibility, short chain fatty acid (SCFA) production, ruminal solubility of Cu, Zn, and Mn, and relative binding strength of trace minerals located in the rumen insoluble digesta fraction. Steers were fed a low-quality grass hay diet (DM basis: 10.8% CP, 63.1% NDF, 6.9 mg Cu/kg, 65.5 mg Mn/kg, and 39.4 mg Zn/kg) supplemented with protein for 21 d. Treatments consisted of 20, 40, and 60 mg supplemental Cu, Mn, and Zn/kg DM, respectively, from either sulfate (STM) or hydroxy (HTM) sources (n=6 steers/treatment). Following a 21-d adaptation period, total fecal output was collected for 5 d. Dry matter digestibility tended (P < 0.07) to be reduced (51.9 vs. 53.4 ± 0.52%) and NDF digestibility was reduced (P < 0.04; 40.4 vs. 42.7 ± 0.67%) in STM vs. HTM supplemented steers. On d-6, rumen fluid was collected at 0, 2, and 4 h post feeding and analyzed for SCFA. There were no treatment x time interactions for any response variables measured. However, treatment was a significant (P < 0.05) source of variation for butyric acid and total SCFA production. Steers receiving HTM had less (P < 0.02) butyric acid and greater (P < 0.05) total SCFA than STM supplemented steers. Steers were then fed the same low-quality grass hay diet without supplemental Cu, Zn, or Mn for 14 d. On d-15, steers received a pulse dose of 20 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either STM or HTM sources (n=6 steers/treatment). Ruminal samples were obtained at 2-h intervals starting at -4 h and ending at 24 h relative to dosing. There was a treatment x time interaction for ruminal soluble Cu, Mn and Zn concentrations. Ruminal soluble mineral concentrations were greater (P < 0.05) for Cu at 4, 6, 8, 10, 12, and 14 h; for Mn at 4 and 6 h; and for Zn at 4, 6, and 8 h post dosing in STM compared to HTM supplemented steers. Concentrations of Cu and Zn in ruminal solid digesta were also affected by treatment, time, and treatment x time. At 12 h post dosing, Cu and Zn concentrations were greater (P < 0.05) in HTM supplemented steers when compared to STM supplemented steers. Upon dialysis against Tris-EDTA the % Zn released was greater at 12 h (P < 0.03) and 24 h (P < 0.05) and the % Cu released was greater (P < 0.02) at 24 h post dosing when compared to STM supplemented steers. Results indicate that Cu and Zn from HTM have low solubility in the rumen, may improve fiber digestibility and appear to be less tightly bound to ruminal solid digesta than Cu and Zn from STM.
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Subject
solubility
trace minerals
steers
digestibility