Lactating cows are routinely treated at dry-off with antibiotic infusions in each quarter for the cure and prevention of pathogenic intramammary infection, which remains the most common disease in dairy herds. This approach is known as blanket dry-cow therapy, usually effective for the prevention and cure of infections, but has been shown to potentially contribute to the emergence and spreading of antibiotic resistant bacterial strains. Exploring the use of non-antibiotic treatments coupled with selective dry-cow therapy is necessary to reduce the risk of antibiotic resistance and potential interference with milk microbiome balance. The impact of selective dry-cow therapy on the physiological milk microbiome needs to be carefully evaluated. In this small-scale trial, five healthy (no mastits, SCC <200,000 cells mL⁻¹) second-parity cows from dry-off to 5 days after calving were sampled. For every cow, each quarter received a different treatment: (i) bismuth salnitrate (internal teat sealant, OrbSeal®, Zoetis, Italy), front right quarter; (ii) cephalonium dihydrate (Cepravin®, MSD, Italy), rear right quarter; (iii) benzathine cloxacillin (Cloxalene dry, Ati, Italy), rear left quarter. No treatment was applied to the remaining quarter (front left) which served as experimental control. For 16S rRNA gene sequencing, bacterial DNA was extracted from 5 ml of milk samples, amplified using the primers for the V3–V4 hypervariable regions and sequenced in one MiSeq (Illumina) run with 2 × 250-base paired-end reads. Bacteriological results confirmed that the quarters were all healthy. The phyla Proteobacteria, Firmicutes, and Actinobacteria were the most abundant for all treatments and controls at all three timepoints, accounting for over 80% of the entire milk microbiota composition. No significant differences were found between treatments and controls in terms of the major alpha and beta diversity indexes, revealing that antibiotic, and non-antibiotic treatments for selective dry-cow therapy did not alter significantly the milk microbiome of dairy cows. The milk microbiota composition showed a clear evolution over the lactation cycle, and the overall changes in the milk microbiota diversity over the lactation cycle were mainly independent of treatments.

哺乳期的母牛通常每季度在干燥时使用抗生素输注进行治疗，以治疗和预防病原性乳房内感染，该疾病仍是奶牛群中最常见的疾病。这种方法被称为毯式干牛疗法，通常对预防和治愈感染有效，但已被证明可能对耐药性细菌菌株的出现和传播产生影响。有必要探索非抗生素疗法与选择性干牛疗法的结合，以降低抗生素耐药性的风险以及对牛奶微生物组平衡的潜在干扰。选择性干牛疗法对生理性牛奶微生物组的影响需要仔细评估。在该小型试验中，五名健康人（无（症，SCC <200,000细胞mL ^-1从干燥到产犊后5天的第二胎牛被取样。对于每头母牛，每季度都接受不同的待遇：（i）右前角硝酸盐铋（内部乳头密封剂，OrbSeal®，Zoetis，意大利）；（ii）二水合头孢鎓（Cepravin®，MSD，意大利），右后四分之一；（iii）苄星霉素氯西林（意大利阿提，Cloxalene dry），左后四分之一。剩余的四分之一（左前）未作任何处理，用作实验对照。对于16S rRNA基因测序，从5 ml牛奶样品中提取细菌DNA，使用V3-V4高变区的引物进行扩增，并在一个MiSeq（Illumina）中进行测序，并进行2×250碱基配对的末端读数。细菌学结果证实这些宿舍都健康。门变形杆菌和 放线菌在所有三个时间点上，所有处理和对照中的糖都是最丰富的，占整个牛奶菌群组成的80％以上。在主要的α和β多样性指数方面，在处理和对照之间没有发现显着差异，这表明选择性干牛疗法的抗生素和非抗生素处理不会显着改变奶牛的牛奶微生物组。牛奶菌群组成在泌乳周期中显示出明显的演变，并且在整个泌乳周期中奶菌群多样性的总体变化主要与处理无关。