RESUMEN
Two experiments were conducted to examine the impact of trace mineral (TM) source on in vitro and in vivo solubility characteristics. Experiment 1: Hydroxy TM (HTM) and sulfate TM (STM) sources of Cu, Mn, and Zn were incubated separately in water for 24 h. Immediately after mixing, initial pH of each solution was greater (P < 0.03) for HTM compared to STM for all elements. Final pH tended to be greater for Cu (P = 0.09) and Zn (P = 0.07) from HTM compared to STM. Water solubility of Cu, Mn, and Zn from STM was greater (P < 0.01) than HTM sources. Experiment 2: Eight steers fitted with rumen cannula were blocked by body weight and randomly assigned to treatments. Treatments consisted of 10 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either STM or HTM sources. Steers were individually fed a cracked corn-corn silage-based diet. Treatments were top-dressed daily. Rumen contents were collected at 0, 2, and 4 h post-feeding on d 1 and 14. On d 15, strained ruminal fluid and particle-associated microorganisms were obtained. Zinc was more tightly bound (P = 0.01) to the digesta in HTM-supplemented steers compared to STM on d 14. These data indicate that TM source influences pH and solubility of Cu, Mn, and Zn in water and may affect rumen soluble Cu concentrations and binding strength of Zn to solid digesta.
RESUMEN
The majority of Mo research has focused on the antagonist effect of Mo, alone or in combination with elevated dietary S, on Cu absorption and metabolism in ruminants. Diets containing both >5.0 mg of Mo/kg DM and >0.33% S have been reported to reduce the Cu status in cattle and sheep. Therefore, due to the potential for inducing Cu deficiency, Mo and S concentrations in the diet should be monitored and kept within appropriate values. Elevated sulfate concentrations in drinking water can also be detrimental to livestock production, especially in ruminants. High concentrations of sulfate in water have been extensively studied in cattle because high-sulfate water induces polioencephalomalacia in ruminants. However, little research has been conducted investigating the impact of Mo in water on Cu metabolism in ruminants. Based on the limited number of published experiments, it appears that Mo in drinking water may have a lower antagonistic impact on the Cu status in cattle when compared to Mo consumed in the diet. This response may be due to a certain percentage of water bypassing the rumen when consumed by ruminants. Therefore, the objective of this review was to examine the impact of Mo in drinking water on cattle performance and Mo and Cu metabolism.
