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.

中文翻译：

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359 优化饲喂肉牛生长和育肥日粮中的钙夹杂物水平


钙 （Ca） 是一种矿物质，在肉牛的许多生化途径和功能中起着至关重要的作用。石灰石是美国饲养和育肥牛的饮食中钙的主要补充来源。初步数据表明，将膳食 Ca 纳入 NASEM（2016 年）要求以及最近咨询营养学家调查报告的平均和模态浓度可能会提高平均日增重 （ADG） 和饲料效率（饲料配给增重;G：F） 的育肥肉牛。因此，本实验的目的是确定当石灰石是添加钙的补充来源时，生长和育肥日粮中钙的最佳浓度。构建了一个数据库，其中包含 89 年至 1963 年发表的 23 个实验中的 2024 种处理方法，其中通过石灰石的膳食 Ca 添加代表处理。构建数据库的搜索参数包括 Ca、石灰石、性能、效率、ADG、G：F、饲养场牛、育肥牛、生长牛和背景牛的组合。在 JMP Pro 17 中使用混合模型分析数据，以确定膳食 Ca 与 ADG、DMI 或 G：F 之间的线性和二次关系，并以随机效应引用。进行了经济敏感性分析，以确定对使用上述模型预计最小化增益成本的膳食 Ca 浓度影响最大的变量。选择膳食钙浓度而不是石灰石作为模型的解释变量，因为在引文调整之前，响应变量中占有更大比例的变化（Ca R2 0.05 至 0.25;石灰石 R2 0.06 至 0.21）。饮食 Ca 浓度与 DMI 无关 （P ≥ 0。75），但饮食 Ca 与 ADG 相关 （R2 = 0.84;RMSE = 0.36;P ≤ 0.03） 和 G：F （R2 = 0.74;RMSE = 0.01;P < 0.01） 以二次方方式。当 Ca 包含在饮食 DM 的 1.20% 时，出现最大 ADG;比 NASEM （2016） 估计的 Ca 需求量高约 2.6 倍。当 Ca 为日粮 DM 的 1.35% 时，增重成本最小。敏感性分析显示，Ca 浓度以最小化增重成本对 DMI、ADG、饲料天数、日粮成本和码数成本的变化敏感。这些结果提供了进一步的证据，表明饲喂比 NASEM（2016 年）目前推荐的用于牛生长和育肥的 Ca 量可能是有益的。未来的笔式饲喂试验是必要的，以验证该荟萃分析的结果，并确定饲喂分级水平 Ca 的牛的剂量反应。还应进行未来的研究，以确定导致观察到的因饲喂增加日粮 Ca 而导致动物性能和效率改善的作用机制。