B. C. Allison, J.W. Spears, M.H. Poore and R. L. McCraw

Chelated and proteinated trace minerals have been shown to improve performance over inorganic trace minerals for both brood cows and grazing cattle in some research trials. They have not been widely tested as supplements for stocker cattle grazing mountain pastures. The objective of this trial was to determine if a mixture of organic trace mineral complexes would improve performance of steers grazing improved mountain pastures.

Experimental Procedures
Eighty-four steers, with an average weight of 601 pounds, were assigned to one of two treatments based on weight and breed. Prior to initiation of the study, steers were identified with eartags, treated for internal and external parasites, vaccinated for IBR, PI3, BVD, BRSV, Pasteurella hemolytica, Haemophilus somnus and clostridial diseases, and implanted with Ralgro®.

Treatments consisted of two different free choice mineral supplements (Table 1). The control mineral supplied all trace elements in inorganic form. The organic mineral supplement supplied two-thirds of the zinc, copper, manganese and cobalt as zinc methio nine, copper lysine, manganese methionine and cobalt glucoheptonate (4-Plex-C®) respectively. There were three replicate groups of cattle per treatment.

Steers were rotated among the six pastures weekly to correct for differences that may have existed among pastures. Two consecutive body weights were ob tained at the beginning and termination of the 112-day study. Interim weights were taken at 28-day intervals. Plasma samples were collected on days 0, 56 and 112 for zinc and copper analyses.

Results and Discussion
Two steers in one control group got out early in the study and remained out of the pasture for a week. Data from these two animals were deleted. One steer in the organic mineral treatment performed very poorly and was also dropped from the study.

Steer gains, mineral intake and an economic analysis are shown in Table 2. For the entire 112-day study, steers receiving the organic mineral tended to gain 4.6% faster than controls, but the difference between treatments was not statistically significant.

Mineral consumption for steers fed the control supplement was 3.8 oz/day. Mineral consumption by steers offered the organic mineral resulted in an average intake of 2.83 oz per day. Of this, 0.226 oz per day was of the concentrated trace mineral source (4-Plex-C®), which is close to the targeted consump tion of .25 ounces per day. Intake of zinc, copper, manganese and cobalt from organic sources averaged 318, 89, 180 and 25 mg per day, respectively.

Assuming that the difference observed among treatments is repeatable, and was due to the different mineral supplements, the cattle on the organic trace mineral supplement returned $2.14/head more than those on the control supplement. Based on this, we could have paid $11.70 more per 50 lb bag of the organic trace mineral supplement than we paid for the inorganic one and still have broken even. Because the differences observed were not statistically significant, however, additional studies need to be conducted before a clear recommendation can be made.

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