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Abstract Calcium (Ca) is a mineral that has an essential role in many biochemical pathways and functions of beef cattle. Limestone is the primary supplemental source of Ca in diets fed to growing and finishing cattle in the United States. Preliminary data indicated that inclusion of dietary Ca above the NASEM (2016) requirements as well as mean and modal concentrations reported by the most recent survey of consulting nutritionists may improve average daily gain (ADG) and feed efficiency (gain to feed ration; G:F) of finishing beef cattle. Thus, the objective of this experiment was to determine the optimal concentration of Ca in growing and finishing diets when limestone was the supplemental source of added Ca. A database was constructed containing 89 treatment means from 23 experiments published from 1963 to 2024 where dietary Ca inclusion via limestone represented treatments. Search parameters to construct the database included a combination of Ca, limestone, performance, efficiency, ADG, G:F, feedlot cattle, finishing cattle, growing cattle, and backgrounding cattle. Data were analyzed in JMP Pro 17 using a mixed model to determine linear and quadratic relationships between dietary Ca and ADG, DMI, or G:F with citation as a random effect. An economic sensitivity analysis was conducted to determine variables most influential to the dietary Ca concentration projected to minimize cost of gain using the above models. Concentration of dietary calcium was selected as the explanatory variable for the models rather than limestone because a greater proportion of variation was accounted for in the response variables prior to the citation adjustment (Ca R2 0.05 to 0.25; limestone R2 0.06 to 0.21). Diet Ca concentration and DMI were unrelated (P ≥ 0.75), but diet Ca was related to both ADG (R2 = 0.84; RMSE = 0.36; P ≤ 0.03) and G:F (R2 = 0.74; RMSE = 0.01; P 0.01) in a quadratic fashion. Maximum ADG occurred when Ca was included at 1.20% of diet DM; approximately 2.6-fold greater than Ca requirements estimated by NASEM (2016). Cost of gain was minimized when Ca was 1.35% of diet DM. Sensitivity analysis revealed Ca concentration to minimize cost of gain was sensitive to changes in DMI, ADG, days on feed, ration cost and cost of yardage. These results provide further evidence that it may be beneficial to feed a greater amount of Ca than currently recommended by the NASEM (2016) for growing and finishing cattle. Future pen-scale feeding trials are warranted to validate the results of this meta-analysis and to determine the dose response of cattle fed graded levels of Ca. Future research should also be conducted to determine the mechanism of action responsible for the observed improvements in animal performance and efficiency resulting from feeding an increased amount of dietary Ca.
Long et al. (Sun,) studied this question.