Preference for inorganic sources of calcium and phosphorus by sheep as a function of need.

We hypothesized that ruminants discriminate among different mineral supplements and modify their selection as a function of need. Forty lambs were offered four-way choices among P, Ca, and Mg sources: monosodium phosphate (MSP), Magnesium phosphate (MGP), Monocalcium phosphate (MCP), and Dicalcium phosphate (DCP); and two-way choices between DCP and the other mineral sources (Baseline). Subsequently, lambs were randomly assigned to four groups (10 lambs/group) and fed rations such that levels of Ca and P were low (LCa_LP), adequate (NCa_NP), low in Ca and adequate in P (LCa_NP), or adequate in Ca and low in P (NCa_LP). Four- and two-way choice tests were repeated (Post-deficiency). During Baseline, lambs ate and preferred MSP > MGP>DCP = MCP (p < .0001), showing that they discriminated among minerals. This pattern remained during four-way Post-deficiency tests, but lambs in LCa_LP, LCa_NP, and NCa_LP showed increased preference for MCP, MGP, and DCP, respectively, relative to other groups and Baseline (p < .05). Some mineral preference also changed in relation to serum concentration of P and Ca. Thus, lambs discriminated among minerals and some groups modified their preferences from Baseline to Post-deficiency choice tests, likely influenced by mineral needs, which in turn contributed to rectify mineral imbalances.