Free choice consumption of minerals by lambs fed calcium-adequate or calcium-deficient diets

Four growth trials were conducted to determine whether lambs have the ability to recognize a dietary Ca deficiency and to correct that deficiency by consuming minerals offered free choice. In trial 1, lambs were fed a control or Ca-deficient diet with 0, 1, 5 or 10 mineral choices, only one of which provided Ca. Daily gains and feed efficiencies of lambs fed control diets tended to be superior to those of lambs fed Ca-deficient diets. Consumption of free choice calcium carbonate was greater (P less than .05) for lambs fed Ca-deficient diets than for those fed control diets. However, total Ca intake was greatest (P less than .05) for lambs fed control diets. In trial 2, lambs were fed diets containing .35, .20 or .06% Ca with zero or four mineral choices in either a constant or varied location. Daily gains were highest (P less than .05) for lambs fed the control diet. Performance of lambs fed diets deficient in Ca was not improved by providing free choice minerals. Although free choice Ca intakes were higher (P less than .05) for lambs fed Ca-deficient diets, total intake of Ca decreased with severity of dietary Ca deficiency. In trial 3, lambs were fed a (1) Ca-adequate diet, (2) Ca-deficient diet, (3) Ca-deficient diet with four mineral choices (one of which contained Ca) or (4) Ca-deficient diet with seven times the daily Ca requirement offered once weekly. Lambs fed control diets gained faster (P less than .05) than those fed deficient diets with free choice minerals. Ca intakes were greater (P less than .05) for control lambs than for those fed Ca-deficient diets with Ca available free choice. In trial 4, lambs were fed either a control or a Ca-deficient diet for 42 d. All lambs were then offered both control and Ca-deficient diets in separate compartments of the feed bunks. Although performance, bone and serum data followed trends similar to those observed in trials 1, 2 and 3, differences between treatment groups were not significant. Data from these trials support the recommendation that, when possible, required minerals should be provided in the diet rather than on a free choice basis.