Abstract
A three-year experiment was designed to determine the mineral status of grazing beef cattle in the Beni region of Bolivia. For year 2 of the trial, pregnancy rates for 655 animals for the salt and salt + bone phosphate treatments were 89.5 and 88.5%, respectively. Second pregnancy rate comparisons (year 3) for 385 animals were 86.4 % for the salt + bone phosphate versus 73.8% for the salt alone treatment. For year 3, steers receiving no minerals had lower (P < 0.01) gains than salt- and salt + bone phosphate-supplemented animals for both the May and October weighings. Males receiving a P source bad heavier weights in May (P < 0.01), with no difference compared with the salt only group in October. Samples of soil, forage, blood serum and liver were analysed for mineral concentrations. From these analyses, seasonal and yearly differences in mineral concentrations were found, with minerals generally in adequate concentrations including K, Mg, Co, Fe and Mn. Ca and Se levels were low during some collection periods and deficient concentrations were found in most samples for P, Na, Cu and Zn.
