Toxy-Nil and Unike Plus Modulate Differences in Gene Expression of Milk Somatic Cells Isolated from Mammary Gland of Lactating Dairy Cows Fed Aflatoxin B1

The objective was to investigate effects of Toxy-Nil (TN) or Unike Plus (UP) on gene expression profiles of blood leukocytes and milk somatic cells (MSC) in dairy cows challenged with dietary aflatoxin B₁ (AFB₁). Sixteen mid-lactation Holstein cows were assigned to receive one of the following treatments: 1) 2.8 mg of AFB₁/cow/day (positive control, PC); 2) 2.8 mg of AFB₁ + 100 g of TN/cow/day; 3) 2.8 mg of AFB₁ + 100 g of UP/cow/day; or 4) no AFB₁ and no adsorbents (negative control, NC). Treatments were administered for 7 days by top-dressing onto a standard TMR diet. Feed and water were available ad libitum throughout the trial. Blood and milk samples were obtained on day 7. Subsequently, mRNA from blood leukocytes and MSC were isolated and sequenced. Genes were considered differentially expressed (DE) when P < 0.001 and FDR ≤ 0.10. There were few differences in gene expression of blood leukocytes. No DE genes were observed when comparing cows not fed AFB₁ to those that were fed AFB₁ (NC vs average of PC/TN/UP). Comparing cows fed AFB₁ alone to cows also receiving adsorbents (PC vs average of TN/UP) revealed one downregulated gene, which was related to mitotic processes and five upregulated genes, which related to nitric oxide generation, signaling, and platelet activation. Comparing TN to UP revealed downregulation of two genes related to platelet activation and iron ion and oxygen binding. In MSC, numerous changes in gene expression were observed. Three annotated genes were DE between NC and TN/UP. No genes were DE between adsorbent treatments (TN vs UP). However, comparing cows not fed AFB₁ to those fed AFB₁ alone (NC vs PC) revealed 120 DE genes, and 70 genes were DE between cows fed AFB₁ without or with adsorbents (PC vs TN/UP). Of those DE genes, 49 were common to the comparisons PC vs NC and PC vs TN/UP. These genes represented functional clusters including glycoproteins and milk proteins, secretion, signaling, protein binding, transporter activity, and response to steroid hormones. Protein domains found to be differentially expressed included a- and b-caseins. Furthermore, approximately 20% of the common DE genes in MSC were mammary gland-specific. In summary, daily feeding of 2.8 mg of aflatoxin B₁ to lactating dairy cows resulted in few DE genes in blood leukocytes, but elicited numerous changes in gene expression in milk somatic cells, many of which were modulated in cows fed TN or UP.