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The objective of this experiment was to evaluate the effects of Mo source (feed or water) on performance and mineral status of cows and calves fed a forage-based diet for two years (DM basis: 6.6% CP; 0.14% S, 6.7 mg Cu/kg, 2.4 mg Mo/kg). Fifty-four cow-calf pairs were stratified by cow age, BW, and liver Cu and Mo status, and randomly assigned to one of six treatments. Treatments consisted of: 1) Negative control (NC; no supplemental Mo or Cu); 2) Positive control [PC: NC + Cu (3 mg Cu/kg diet DM from CuSO4·5H2O)]; 3) NC + 500 µg Mo/L from MoNa2O4·2H2O in drinking water (Mo 500-water); 4) NC + 1000 µg Mo/L of MoNa2O4·2H2O in drinking water (Mo 1000-water); 5) Mo 1000-water + 3 mg Cu/kg diet DM from CuSO4·5H2O (Mo 1000-water+Cu); and 6) NC + 3 mg Mo/kg diet DM from MoNa2O4·2H2O (3.0 Mo-diet). Cattle were allowed ad-libitum access to feed, water, and a protein supplement throughout the experiment. During the winter months animals were housed in three replicate pens per treatment and during the summer months animals were housed in separate pastures by treatment where cow and calf feed and water intake could be measured separately. Data were analyzed as a completely randomized block design. Throughout the experiment no signs of molybdenosis were observed. There was a treatment x time (P < 0.01) interaction for cow liver Cu concentrations. Cows not receiving supplemental Cu had lower (P < 0.01) liver Cu concentrations than cows receiving supplemental Cu. Cow and calf performance, calf mineral status, cow liver Mo, and plasma and milk Mo and Cu concentrations were similar across treatments. These data indicate that Mo supplemented in water or feed at concentrations used in this experiment had minimal impact on Cu status and overall animal performance.

Fifty-four multiparous beef cows were used to examine the effect of molybdenum (Mo) supplemented in drinking water or feed on offspring performance. Cows were blocked by body weight (BW) and age into one of 6 groups. Group were then randomly assigned to treatment. Treatments consisted of: 1) Control (no supplemental Mo or Cu), 2) Control+Cu (3 mg Cu/kg DM from CuSO4·5H2O added to the basal diet), 3) Control + 500 µg Mo/L from MoNa2O4·2H2O in drinking water (Mo 500-water), 4) Control + 1000 µg Mo/L of MoNa2O4·2H2O in drinking water (Mo 1000-water), 5) Mo 1000-water plus 3 mg Cu/kg DM from CuSO4·5H2O added to the basal diet (Mo 1000-water+Cu, and 6) Control plus 3 mg Mo/kg DM from MoNa2O4·2H2O added to the basal diet (3.0 Mo-diet). Cows were housed in dry lot pens (n = 3 cows/pen; 3 pens/treatment) and fed a low-quality grass hay diet (DM basis: 6.6% CP; 0.14% S, 6.2 mg Cu/kg, 2.3 mg Mo/kg) and a protein supplement (30% CP). Cows received their respective treatments beginning 60 d prior to breeding and remained on treatments until all calves were weaned at approximately 7 mo. of age. Calf birth weights were collected on the day of birth and all calves were weaned on the same day. Data were analyzed using a mixed effects model for a completely randomized block design. Birthweight, ADG, and 205d adjusted weaning weights were similar (P > 0.05) across treatments. These data indicate that Mo supplemented in the drinking water or the diet regardless of the inclusion of additional Cu did not impact calf performance through weaning.

Twelve Angus steers were utilized to investigate the influence of molybdenum (Mo) in drinking water or feed on apparent absorption and retention of copper (Cu) and Mo. Steers were fed a low-quality grass hay diet for 14 days. Steers were then housed in individual metabolism stalls and blocked by body weight and dry matter intake (DMI) and randomly assigned within block to one of three treatments. Treatments consisted of (1) control (no supplemental Mo), (2) 5.0 mg Mo/kg DM from sodium molybdate dihydrate (Mo-diet), and (3) 1.5 mg Mo/L from sodium molybdate dihydrate delivered in the drinking water (Mo-water). Total fecal and urine output were then collected for 5 days. Dry matter, Cu and water intake, and DM digestibility were similar across treatments. Molybdenum intake was greater (P

Eighty-nine American Wagyu steers were used to evaluate the effects of dietary barley supplementation on feedlot performance. We hypothesized that barley supplementation would increase ADG compared to non-supplemented control animals. The experimental design was a randomized complete block design. Steers were blocked by initial body weight (BW) and randomly assigned within block to one of two treatments. Treatments consisted of 1) Control (no supplemental barley) and 2) Control diet + 0.9 kg∙animal-1∙d-1 of supplemental barley. Steers were housed in feedlot pens (all pens contained n = 4 steers/pen with the exception of one Control pen that contained n=5 steers; 11 replicates/treatment; experimental unit = pen) and fed a traditional American Wagyu finishing diet (DM basis: 68.42% DM, 14.33% CP; TDN: 74.76%, NEg: 1.16 Mcal/kg, 5.25% EE) for 270d. The basal diet consisted of grass hay, corn silage, cracked corn grain, soybean meal, corn distillers grain, white salt, ground limestone, and olive byproduct. Diets were fed once daily in the morning and barely was top dressed to the appropriate pens, immediately after the basal diet was delivered. Steers were individually weighed on d -1 and 0, and approximately every 28 days throughout the 270d experiment. Data were analyzed using a mixed effects model (PROC MIXED, SAS) for a completely randomized block design. Initial pen BW was used as a covariate in the statistical analysis of all performance data and significance was determined at P ≤ 0.05. Initial and final BW, ADG, DMI, and feed:gain were similar across treatments. Therefore, under the conditions of this experiment, these data suggest that barley supplementation for 270d to American Wagyu cattle did not impact overall animal performance.

Twelve crossbred steers fitted with rumen cannulae were used to determine the influence of trace mineral (TM) source on relative binding strength of minerals in the ruminal insoluble digesta fraction (IDF). Steers (n = 4/treatment) were fed a corn silage-based diet containing no supplemental Cu, Mn, and Zn for 7d. On d 8, steers received a bolus dose (2 x NRC requirement) of the respective TM from sulfate (STM), organic (ORG; provided as Zn methionine, Mn methionine, and Cu lysine), or hydroxy TM (HTM; Micronutrients USA LLC) sources. Ruminal samples were obtained at 2 h intervals starting at -4 and ending at 24 h post dosing. Ruminal samples were centrifuged and supernatant and the IDF were collected and frozen separately. Binding strength of Cu, Mn, and Zn to the IDF was estimated at 0, 12, and 24 h using dialysis against 0.05 M Tris-EDTA. At 0 h pre-dosing, IDF concentrations of Cu, Mn, and Zn were similar across treatments. At 12 h post dosing Cu and Zn IDF concentrations were greater (P < 0.05) in HTM vs. STM and ORG supplemented steers, and Mn concentrations were greater (P < 0.05) in HTM and ORG vs. STM supplemented steers. At 24 h post dosing, IDF Zn concentrations were greater (P < 0.05) in HTM vs STM and ORG supplemented steers and Cu and Mn concentrations were similar across treatments. At 12 and 24 h post dosing the percent Cu and Zn released following dialysis was greater (P < 0.05) in HTM vs STM and ORG supplemented steers. The percent released of Cu, Mn, and Zn at 0 h, and Mn at 12 and 24 h were similar across treatments. Data indicate that a greater concentration of Cu and Zn from HTM is loosely bound to the ruminal IDF.

Simple Summary The majority of research examining the antagonist impact of molybdenum (Mo) on copper (Cu) absorption and metabolism in ruminants has been conducted by supplementing dietary Mo, alone or in combination with elevated dietary sulfur (S) concentrations, and monitoring the Cu status of the animals. However, little research has been conducted investigating the impact of Mo in water on Cu metabolism in ruminants. Based on the limited number of experiments available for this review, it appears that Mo in drinking water may have a lower antagonistic impact on Cu status in cattle when compared to Mo consumed in the diet. Therefore, this review will focus on the impact of Mo in drinking water on cattle performance and Mo and Cu metabolism. Abstract 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.