Effects of varying sources of Cu, Zn, and Mn on mineral status and preferential intake of salt-based supplements by beef cows and calves and rainfall-induced metal loss

Abstract

Three studies were completed to evaluate the effects of Cu, Zn, and Mn source on preferential intake, trace mineral status and rainfall-induced metal loss of salt-based mineral supplements. Mineral supplements were formulated to contain 2,500, 5,500, and 4,000 mg/kg of Cu, Zn, and Mn, respectively. Supplements differed only by source of Cu, Zn, and Mn, which were hydroxychloride, organic, or sulfate sources. In Exp. 1, the 3 formulations were offered simultaneously for 18 wk to pre-weaned beef calves (4 pastures; 17 calves/pasture) within separate containers inside covered cow-exclusion areas. Consumption averaged 21 ± 2.4 g/calf daily (sum of all 3 sources), with a greater (P < 0.001) percentage of the total intake coming from the hydroxychloride- vs. organic- or sulfate-sources of Cu, Zn, and Mn. In Exp. 2, the same sulfate and hydroxychloride formulations were randomly assigned to pastures (n = 4 pastures/treatment) containing 18 to 20 cow-calf pairs/pasture. Treatments were offered for 20 wk within covered areas designed to assess cow and calf intake separately. At weaning, liver biopsies were collected from 4 cow-calf pairs/pasture (n = 16 cows and calves/treatment). Source of Cu, Zn, and Mn had no effect on voluntary mineral intake among calves (P = 0.44) and cows (P = 0.14). Calves consuming mineral containing hydroxychloride-sources of Cu, Zn, and Mn tended (P = 0.06) to have greater ADG over the 20-wk period compared to calves consuming sulfate-sources of the same elements (1.09 vs. 1.06 kg/d; SEM = 0.013). Mineral status of cows and calves was not affected (P ≥ 0.17) by source of Cu, Zn, and Mn. In Exp. 3, each of the mineral formulations from Exp. 1, were exposed to a 10.2 cm precipitation event delivered in three equal 3.4 cm applications within a week. To accomplish this, 750 g of mineral was placed into Buchner funnels (177 cm 2) on 20 to 25 µm pore filter paper. Deionized water (pH adjusted to 5.6) was poured over the mineral. Total leaching losses of Cu, Zn, and Mn were less (P < 0.001) for formulations containing hydroxychloride- vs. organic- and sulfate-sources. These results imply that, when offered a choice, calves preferentially consume mineral supplements formulated with hydroxychloride vs. sulfate or organic sources of Cu, Zn, and Mn. In addition, hydroxychloride sources of Cu, Zn, and Mn are less susceptible to rainfall-induced leaching losses compared to sulfate and organic sources.

Trace Mineral Nutrition of Grazing Beef Cattle

“…This theory was further examined in a later study [102] where beef calves were shown to preferentially consume creep feed supplements fortified with hydroxychloride vs. sulfate or organic sources of Cu, Zn, and Mn. Further studies support this preferential intake behavior in other supplementation strategies common for grazing beef cattle, such as cooked molasses tubs [103] and free-choice, salt-based supplements [104]. In the latter study [104], trace mineral solubility was assessed in a rainfall simulation model.…”