Morphological Examination and Transcriptomic Profiling To Identify Prednisolone Treatment in Beef Cattle

Development of a droplet digital PCR assay to detect illicit glucocorticoid administration in bovine

Glucocorticoids are often used illegally in food-producing animals for the growth promotion of livestock animals. In accordance to official chemical methods for glucocorticoid detection, an animal is declared as non-compliant when a residue is identified in the sample. Neverthless, growth promoting molecules can often escape identification due to their rapid elimination or due to the use of non-detectable new generation drugs. Therefore, an indirect screening method able to detect the biological effect of long-term administration of low doses of dexamethasone and prednisolone on livestock has been developed to support official methods. As already described, FKBP5 (FKBP prolyl isomerase 5) expression in bovine thymus is regulated by glucocorticoids, and this specific regulation can be exploited in an indirect screening assay. In the present study, male veal calves and young bulls were considered in three different trials in which estradiol, dexamethasone, and prednisolone were administered alone or in combination with Revalor-200 subcutaneous pellets. Thoracic thymus was sampled from all animals and molecular analysis was performed. A duplex droplet digital PCR assay with EvaGreen^® was employed to detect the target gene expression using absolute quantification. The developed droplet digital PCR assay was precise, showing intra- and inter-assay mean coefficient of variation values of about 6.16% and 3.17%, respectively. It was also highly specific (100%) with Youden’s index of 76.92% and 53.57% applied to veal calves and young bulls, respectively. The lowest detection limit in which the target gene expression level was kept constant, was 0.05 ng/μl of cDNA with 1 copies/μL and 0.5 copies/μL for target and reference gene, respectively. This study establishes the basis for using a digital PCR-based assay as an efficient test to identify animals illegally treated with glucocorticoids.

Tracing Recombinant Bovine Somatotropin Ab(Use) Through Gene Expression in Blood, Hair Follicles, and Milk Somatic Cells: A Matrix Comparison

The use of recombinant bovine somatotropin (rbST) in dairy cattle is forbidden in the European Union. Due to the very low circulating concentration of rbST in treated animals, its direct detection is still a challenge. Therefore, the use of indirect methods to detect the ab(use) of rbST in dairy cattle appears as a good alternative. In the past few years, gene expression demonstrated its utility in screening the use of illicit substances in both humans and animals. In this study, a comparison of three types of matrices (milk somatic cells, blood, and hair follicles) was carried out to evaluate their potential use for routine control of rbST using 15 gene-expression profiles. A total of six rbST-treated cows and three control cows were included in the study. A subcutaneous injection containing 500 mg of rbST was administered to the treated group. Samples of the three matrices were collected before rbST administration, and at three and nine days after treatment. The quality of RNA extracted was higher in the blood and hair-follicle samples than in the milk somatic cells. In the three matrices, there were significant differences in the expression of some genes, with milk somatic cells and blood presenting the the best matrices. On this note, the cyclin D1 (CCND1), interleukin 1 beta (IL-1β), tumor necrosis factor (TNF), and insulin-like growth factor 1 receptor (IGF-1R) genes showed potential as biomarkers of rbST treatment. Therefore, blood, somatic cells, and follicle hair should be considered as promising sources of RNA, and can be used in gene-expression assays to routinely control the illicit use of rbST.

Reference Gene Selection and Prednisolone Target Gene Expression in Adipose Tissues of Friesian Cattle

Corticosteroids are frequently used in livestock production, and their use is permitted by the European Union for therapeutic purposes only. However, small doses of corticosteroids are often administered in meat-producing animals to improve zootechnical performance. Prednisolone is one of the most commonly used corticosteroids with a growth-promoting purpose in animal husbandry. This study proposes to identify a gene whose expression is significantly regulated by prednisolone in visceral and subcutaneous adipose tissues. The analysis was conducted on Friesian cattle treated with prednisolone (30 mg day^-1). The reference gene expression stability and optimal number for gene expression normalization were calculated. Family with sequence similarity 107 member A (FAM107A) and pyruvate dehydrogenase kinase 4 are the prednisolone target genes identified in adipose tissue. FAM107A was downregulated by ∼2.9-fold by prednisolone in subcutaneous adipose tissue. This result suggests that FAM107A could be a possible indirect biomarker of prednisolone treatment in cattle and encourages a deeper investigation in this direction.