Prados L F, Sathler D F T, Silva B C, Zanetti D, Valadares Filho S C, Alhadas H M, Detmann E, Santos S A, Mariz L D S, Chizzotti M L
J Anim Sci. 2017 Apr;95(4):1766-1776. doi: 10.2527/jas.2016.1085.
Weaned Nellore bulls ( = 36; 274 ± 34 kg) were used in a randomized block design with a 2 × 2 factorial arrangement of treatments to evaluate intake, fecal excretion, and performance with different concentrations of minerals. Experimental diets were formulated with 2 concentrations of Ca and P (macromineral factor; diet supplying 100% of Ca and P according to BR-CORTE () [CaP+] or diet without limestone and dicalcium phosphate [CaP-]) and 2 concentrations of microminerals (micromineral factor; diet with supplementation of microminerals [Zn, Mn, and Cu; CuMnZn+] or diet without supplementation of microminerals [Zn, Mn, and Cu; CuMnZn-]). The factor CaP- was formulated without the addition of limestone and dicalcium phosphate, and the factor CuMnZn- was formulated without inorganic supplementation of microminerals (premix). The diets were isonitrogenous (13.3% CP). Intake was individually monitored every day. Indigestible NDF was used as an internal marker for digestibility estimates. The bulls were slaughtered (84 or 147 d on feed), and then carcass characteristics were measured and liver and rib samples were collected. Feed, feces, rib bones, and liver samples were analyzed for DM, ash, CP, ether extract (EE), Ca, P, Zn, Mn, and Cu. There were no significant interactions ( ≥ 0.06) between macro- and micromineral supplementation for any variables in the study. Calcium, P, and micromineral concentrations did not affect ( ≥ 0.20) intake of DM, OM, NDF, EE, CP, TDN, and nonfiber carbohydrates (NFC). Calcium and P intake were affected ( < 0.01) by macromineral factor. Animals fed without Ca and P supplementation consumed less of these minerals. Dry matter and nutrient fecal excretion (OM, NDF, EE, CP, and NFC) were similar ( ≥ 0.23) among all factors. Performance and carcass characteristics were similar ( ≥ 0.09) among diets. The content of ash in rib bones was not affected by diets ( ≥ 0.06). Plasma P and phosphatase alkaline concentrations were similar ( ≥ 0.52) among diets. Supplementation of microminerals decreased ( < 0.01) plasma Ca concentration; nevertheless, all analyzed blood metabolites were within the reference values. Supplementation of Ca and P increased ( < 0.01) fecal excretion of these minerals. These results indicate that mineral supplementation (Ca, P, Zn, Mn, and Cu) of conventional feedlot diets for Nellore bulls may be not necessary. Dietary reductions in these minerals would represent a decrease in the cost of feedlot diets. Dietary reduction in Ca and P content cause a decrease in fecal excretion of these minerals, which, in turn, represents an opportunity to reduce the environmental impact of feedlot operations.
断奶的内洛尔公牛（n = 36；体重274±34千克）采用随机区组设计，按2×2析因处理安排，以评估不同矿物质浓度下的采食量、粪便排泄量和生产性能。实验日粮根据钙和磷的2种浓度（常量矿物质因素；按照巴西肉牛营养需要量标准（BR-CORTE）提供100%钙和磷的日粮[CaP+]，或不添加石灰石和磷酸氢钙的日粮[CaP-]）以及2种微量元素浓度（微量元素因素；添加微量元素[锌、锰和铜；CuMnZn+]的日粮，或不添加微量元素[锌、锰和铜；CuMnZn-]的日粮）进行配制。CaP-因素日粮的配制不添加石灰石和磷酸氢钙，CuMnZn-因素日粮的配制不进行无机微量元素预混料添加。日粮粗蛋白含量均为13.3%。每天单独监测采食量。使用中性洗涤纤维不可消化部分作为消化率估算的内源性标记物。公牛在采食84天或147天后屠宰，然后测量胴体特性并采集肝脏和肋骨样本。对饲料、粪便、肋骨和肝脏样本进行干物质、灰分、粗蛋白、乙醚提取物（EE）、钙、磷、锌、锰和铜的分析。本研究中，常量和微量矿物质添加之间对任何变量均无显著交互作用（P≥0.06）。钙、磷和微量元素浓度对干物质、有机物、中性洗涤纤维、乙醚提取物、粗蛋白、总可消化养分和非纤维碳水化合物（NFC）的采食量均无影响（P≥0.20）。常量矿物质因素对钙和磷的采食量有影响（P<0.01）。未补充钙和磷的动物对这些矿物质的摄入量较少。所有因素之间的干物质和养分粪便排泄量（有机物、中性洗涤纤维、乙醚提取物、粗蛋白和NFC）相似（P≥0.23）。不同日粮间的生产性能和胴体特性相似（P≥0.09）。日粮对肋骨灰分含量无影响（P≥0.06）。不同日粮间血浆磷和碱性磷酸酶浓度相似（P≥0.52）。添加微量元素会降低（P<0.01）血浆钙浓度；不过，所有分析的血液代谢物均在参考值范围内。添加钙和磷会增加（P<0.01）这些矿物质的粪便排泄量。这些结果表明，对内洛尔公牛常规育肥日粮补充矿物质（钙、磷、锌、锰和铜）可能没有必要。日粮中减少这些矿物质含量将降低育肥日粮成本。日粮中钙和磷含量的降低会导致这些矿物质粪便排泄量减少，这反过来又为降低育肥场运营对环境的影响提供了契机。
