PSXII-18 The influence of molybdenum in drinking water or feed on apparent absorption and retention of molybdenum and copper in beef steers

Abstract

Abstract Twelve Angus steers (BW 694.1 ± 47.4 kg) fitted ruminal cannulae were used to examine the effect of molybdenum (Mo) supplemented in drinking water or feed on apparent absorption and retention of Mo and copper (Cu). Steers were fed a low-quality grass hay diet (DM basis: 6.5% CP; 0.13% S, 3.4 mg Cu/kg, 2.4 mg Mo/kg) for 14 d. Steers were then housed in individual metabolism stalls for 3 d to determine DMI. Steers were then blocked by BW and DMI and randomly assigned within block to one of three treatments (n = 4 steers per treatment). 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). After the 3d DMI determination period, total fecal and urine output was collected for 5 d. Dry matter intake and DM digestibility were similar across treatments. Data were analyzed using a mixed effects model (PROC MIXED, SAS) for a completely randomized block design. Apparent absorption of Cu was greater (P < 0.05) in Control and Mo-water steers when compared to Mo-diet steers. Apparent retention of Cu was greater (P < 0.05) in Control steers when compared to Mo-diet steers. Steers receiving Mo-water had a similar apparent retention of Cu when compared to Control and Mo-diet steers. By design, treatment was a significant (P < 0.01) source of variation for Mo intake. Control steers had lesser (P < 0.05) Mo intake when compared to Mo-diet and Mo-water supplemented steers. Apparent absorption and retention of Mo were greater (P < 0.05) in Mo-diet steers compared to Control and Mo-water steers. These data indicate that Mo metabolism and apparent absorption of Cu are different when Mo is supplemented in water relative to feed.