The effect of feeding inorganic and organic selenium sources on the performance and content of selenium in milk of transition dairy cows

ABSTRACT. The aim of this study was to determine the effects of supplementing close-up and fresh dairy cows’ diets with sodium selenite or organic sources of selenium (Se) on the dry matter intake (DMI), milk production and composition. Based on their body condition score (BCS), previous lactation milk yield and expected calving date, 24 multiparous Holstein dairy cows were balanced and randomly assigned to 4 experimental treatments. Experimental treatments were: control (basal diet without Se supplementation with 0.10 and 0.15 mg of Se kg-1 DM in close-up and fresh diets, respectively), sodium selenite supplementation (0.50 mg of Se kg-1 DM; Se-S), selenium yeast supplementation (0.50 mg of Se kg-1 DM; Se-Y) and selenomethionine supplementation (0.50 mg of Se kg-1 DM; Se-M). Neither Se supplementation nor Se source affected DMI pre- and postpartum. Milk production and composition were not different across Se sources, but concentrations of Se in milk were 14 and 10% greater for cows fed Se-M and Se-Y than for those fed control, respectively. Cows fed Se-M had lower somatic cell count than control (SCC; 173.11 vs. 318.89 cells × 103 Ml-1). The changes of BW and BCS pre- and postpartum were not affected by treatments over experimental period. The results of present study showed that selenomethionine supplementation compared to other sources decreased SCC in transition cows. In addition, milk Se concentrations increased in Se-Y and Se-M groups more significantly compared to the Se-S group. This indicates that organic Se had better replace inorganic Se for transition dairy cows.

摘要：本研究旨在探究为干奶后期与泌乳初期奶牛的日粮添加亚硒酸钠或有机硒源，对其干物质采食量（dry matter intake, DMI）、产奶量及乳成分的影响。本研究基于受试奶牛的体况评分（body condition score, BCS）、上一泌乳期产奶量以及预期产犊日期，将24头经产荷斯坦奶牛进行均衡配对后，随机分配至4个试验组。试验组分别为：对照组（基础日粮不额外添加硒，干奶后期与泌乳初期日粮中的硒含量分别为0.10 mg·kg⁻¹干物质和0.15 mg·kg⁻¹干物质）、亚硒酸钠添加组（日粮硒添加量为0.50 mg·kg⁻¹干物质，记为Se-S）、酵母硒添加组（日粮硒添加量为0.50 mg·kg⁻¹干物质，记为Se-Y）以及硒蛋氨酸添加组（日粮硒添加量为0.50 mg·kg⁻¹干物质，记为Se-M）。无论是否添加硒以及硒源类型，均未对产前后的干物质采食量产生显著影响。不同硒源对产奶量及乳成分均无显著影响，但饲喂Se-M与Se-Y组奶牛的乳硒含量分别较对照组高出14%与10%。饲喂Se-M组奶牛的体细胞数（somatic cell count, SCC）显著低于对照组（分别为173.11 × 10³ cells·mL⁻¹与318.89 × 10³ cells·mL⁻¹）。试验期间，受试奶牛的体重与体况评分的产前后变化均不受试验处理的影响。本研究结果表明，与其他硒源相比，添加硒蛋氨酸可降低围产期奶牛的体细胞数。此外，与Se-S组相比，Se-Y与Se-M组的乳硒含量提升更为显著。这说明对于围产期奶牛而言，有机硒相较于无机硒具有更优的替代效果。