The interaction of monensin and 2 supplemental Mg sources (MgO and MgSO₄) on total-tract digestion of minerals and organic nutrients and milk production was evaluated in lactating dairy cattle. Eighteen multiparous Holstein cows (139 ± 35 DIM) were used in a split-plot experiment with 0 or 14 mg/kg diet DM of monensin as the whole-plot treatments and Mg source as split-plot treatments. During the entire experiment (42 d), cows remained on the same monensin treatment but received a different Mg source in each period (21 d) of the Latin square. Diets were formulated to contain 0.35% Mg with about 40% of that provided by MgO or MgSO₄. Diets were formulated to have similar concentrations of major nutrients and K concentrations were elevated (2.1% of DM) with K₂CO₃ to create antagonism to Mg absorption. Apparent digestibility was measured by total collection of urine and feces. Supplemental MgSO₄ decreased DMI (26.9 vs. 25.7 kg/d) and tended to decrease milk yield (40.2 vs. 39.3 kg/d), but increased the digestibility of OM (68.3 vs. 69.2%) and starch (91.9 vs. 94.4%) compared with MgO. Feeding MgSO₄ with monensin decreased NDF digestibility compared with other treatments (46.7 vs. 50.2%). That diet also had decreased apparent absorption of Mg compared with diets without monensin (15.6 vs. 19.2%), whereas MgO with monensin had greater apparent absorption of Mg (23.0%) than other treatments. Cows consuming MgSO₄ had increased apparent Ca absorption (32.2 vs. 28.1%) and balance. A diet with MgSO₄ without monensin increased the concentration of long-chain fatty acids in milk, suggesting increased mobilization of body fat or decreased de novo fatty acid synthesis in the mammary gland. Overall, when dietary Mg was similar, MgO was the superior Mg source for lactating dairy cattle, but inclusion of monensin in diets should be considered when evaluating Mg sources.

在泌乳的奶牛中，评估了莫能菌素和2种补充Mg来源（MgO和MgSO ₄）在矿物质和有机营养物的总消化中的相互作用以及产奶量。将十八只多头荷斯坦奶牛（139±35 DIM）用于分裂地块试验，采用0或14 mg / kg日粮DM莫能菌素作为整个地块处理，而Mg来源作为分裂地块处理。在整个实验中（42 d），奶牛仍接受相同的莫能菌素处理，但在拉丁方格的每个时期（21 d）均接受不同的Mg来源。日粮中的镁含量为0.35％，其中MgO或MgSO ₄的含量约为40％。日粮中的主要营养素含量相似，且K ₂ CO的钾含量升高（DM的2.1％）₃对镁的吸收产生拮抗作用。表观消化率通过尿液和粪便的总收集量来测量。补充MgSO ₄降低DMI（26.9 vs. 25.7 kg / d）并降低牛奶产量（40.2 vs. 39.3 kg / d），但增加了OM（68.3 vs. 69.2％）和淀粉（91.9 vs. 94.4）的消化率。 ％）与MgO相比。与其他处理相比，用莫能菌素饲喂MgSO _4会降低NDF的消化率（46.7对50.2％）。与不含莫能菌素的饮食相比，该饮食也降低了镁的表观吸收（15.6比19.2％），而含莫能菌素的MgO的表观镁吸收（23.0％）高于其他处理。消耗MgSO _4的母牛的表观钙吸收增加（32.2对28.1％）和平衡。含镁饮食不含莫能菌素的_4会增加牛奶中长链脂肪酸的浓度，表明乳腺中体脂的动员增加或从头脂肪酸合成减少。总体而言，当饮食中的镁含量相似时，MgO是泌乳奶牛的优质Mg来源，但是在评估Mg来源时应考虑在饲料中添加莫能菌素。