The effect of trace mineral source and concentration on ruminal digestion and mineral solubility

The objective of this experiment was to compare the effect of sources of sulfate trace mineral (STM) and hydroxy trace mineral (HTM) at different inclusions on digestibility of dry matter (DM) and neutral detergent fiber and solubility of Cu, Mn, and Zn in the rumen and abomasum of cattle. Five ruminally cannulated steers were used in a 5 × 5 Latin square design and individually fed a corn silage-based diet on an ad libitum basis. The 5 dietary treatments were as follows: control: no supplemental Cu, Mn, or Zn, analyzed to contain 7.4 mg of Cu, 30.8 mg of Mn, and 32.1 mg of Zn per kilogram of diet DM (CON); low sulfate: 5 mg of Cu/kg of DM supplemented from CuSO4, 15 mg of Mn/kg of DM from MnSO4, and 30 mg of Zn/kg of DM from ZnSO4; low HTM: 5 mg of Cu/kg of DM supplemented from basic copper chloride (IntelliBond C; Micronutrients Inc., Indianapolis, IN), 15 mg of Mn/kg of DM from manganese hydroxychloride (IntelliBond M; Micronutrients Inc.), and 30 mg of Zn/kg of DM from zinc hydroxychloride (IntelliBond Z; Micronutrients Inc.); high sulfate: 25 mg of Cu/kg of DM supplemented from CuSO4, 60 mg of Mn/kg of DM from MnSO4, and 120 mg of Zn/kg of DM from ZnSO4; and high HTM: 25 mg of Cu/kg of DM supplemented from basic copper chloride, 60 mg of Mn/kg of DM from manganese hydroxychloride, and 120 mg of Zn/kg of DM from zinc hydroxychloride. Periods lasted for 12 d, with 10 d of diet adaptation. Dacron bags containing the CON total mixed ration were inserted on d 11 at 0 h and were removed at 6, 12, 24, and 36 h after insertion. Dry matter and neutral detergent fiber disappearances and rumen and simulated abomasal trace mineral solubilities were evaluated. Dietary treatment did not affect DM intake. Dry matter disappearance was lesser in supplemental TM treatments and greater in CON than the STM treatments, although the CON and HTM treatments did not differ. Neutral detergent fiber disappearance was not affected by treatment. Ruminally soluble Cu and Mn concentrations were least in CON and were lesser in HTM-containing treatments compared with STM treatments. However, in the abomasum, solubilities of Cu and Mn were similar across trace mineral sources. Ruminal and simulated abomasal soluble Zn was greater in the HTM treatments than in CON and STM, driven by the greater solubility of the high HTM treatment. Under the conditions of this study, supplementing trace minerals as STM decreased DM digestibility, whereas HTM did not affect DM digestibility. Additionally, Cu and Mn from HTM sources were relatively insoluble in the rumen but had similar solubility as STM at the pH found in the abomasum, suggesting that these minerals should be available for absorption in the intestine.