Department of Animal Biosciences, Ontario Agricultural College, University of Guelph, Guelph, ON, Canada N1G 2W1.
Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6G 2R3.
J Dairy Sci. 2024 Aug;107(8):6211-6224. doi: 10.3168/jds.2023-24283. Epub 2024 Mar 8.
Selenium is an essential trace mineral for dairy cattle and can be provided in the diet in various forms that may differ in bioavailability. The objective of this study was to determine how source of Se affects animal performance, Se status, retention, and apparent and true absorption. Multiparous Holstein cows (n = 24; 597 ± 49 kg of BW) were blocked by DIM (161 ± 18) and randomly assigned to receive 0.3 mg Se/kg of DM (100% of National Academies of Sciences, Engineering, and Medicine requirements) of either organic Se (ORG; selenized yeast) or inorganic Se (INO; sodium selenite). The Se premix was top dressed on a common TMR fed daily and mixed into the top 15 cm directly before feeding. Following an 11-wk adaptation period, cows received simultaneous infusions of an intraruminal isotope dose of Se in the same chemical form as the premix, and an intravenous dose of Se in an inorganic form. Infusions were followed by a 4-d period of blood and rumen fluid sampling, and total collection of feces, urine, and milk. Daily DMI (23 ± 0.6 kg), milk yield (35 ± 1.2 kg), and serum Se (0.11 ± 0.003 µg/g) were not different between treatments during the adaptation period, but milk Se concentrations were greater for ORG compared with INO. Serum Se maximum concentration and area under the curve (AUC) were not different between treatments for 72 h following infusion, but rumen fluid Se AUC was higher for ORG than INO. Apparent absorption (64% ± 1.4%), and retention (44% ± 1.5%) of the Se dose did not differ between treatments. True absorption was calculated using Se enrichment in serum and feces and was determined to be 69% ± 1.3% and did not differ between treatments. Fecal excretion of the Se dose was not different between treatments (36% ± 1.4%), but ORG had lower urinary excretion and higher milk excretion compared with INO. These results indicate that organic Se resulted in greater Se concentration of milk and lower urinary Se excretion into the environment, but absorption, Se status, and performance of the cow were not affected by Se source at this supplementation level.
硒是奶牛的必需微量元素，可以以不同的形式提供给奶牛，这些形式的生物利用度可能不同。本研究的目的是确定硒的来源如何影响动物的生产性能、硒的状态、保留率以及表观和真吸收。将 24 头（597 ± 49 kg BW）经产荷斯坦奶牛按 DIM（161 ± 18）分组，随机接受 0.3 mg/kg DM（100%满足美国国家科学院、工程院和医学院的需求）的有机硒（酵母硒）或无机硒（亚硒酸钠）。硒预混料添加在每日饲喂的普通 TMR 中，并在饲喂前直接混入顶层 15cm 处。在 11 周的适应期后，奶牛接受瘤胃内同位素剂量的硒和静脉内无机形式的硒同时输注。输注后进行 4 天的血液和瘤胃液取样以及粪便、尿液和牛奶的总收集。在适应期内，两种处理方式的奶牛日采食量（23 ± 0.6 kg）、产奶量（35 ± 1.2 kg）和血清硒（0.11 ± 0.003 µg/g）均无差异，但有机硒组的牛奶硒浓度高于无机硒组。输注后 72 小时内，两种处理方式的血清硒最大浓度和曲线下面积（AUC）无差异，但有机硒组的瘤胃液硒 AUC 高于无机硒组。硒剂量的表观吸收（64% ± 1.4%）和保留率（44% ± 1.5%）在两种处理方式之间无差异。真吸收是通过血清和粪便中的硒富集来计算的，确定为 69% ± 1.3%，且在两种处理方式之间无差异。硒剂量的粪便排泄量在两种处理方式之间无差异（36% ± 1.4%），但有机硒组的尿硒排泄量较低，而牛奶排泄量较高。这些结果表明，有机硒提高了牛奶中的硒浓度和环境中的尿硒排泄量较低，但在这种补充水平下，硒的来源对吸收、硒的状态和奶牛的性能没有影响。
