Adrenocortical Response in Cows after Intramuscular Injection of Long-Acting Adrenocorticotropic Hormone (Tetracosactide Acetate Zinc Suspension)

Genome-Wide DNA Methylation and Gene Expression Profiles in Cows Subjected to Different Stress Level as Assessed by Cortisol in Milk

Dairy cattle health, wellbeing and productivity are deeply affected by stress. Its influence on metabolism and immune response is well known, but the underlying epigenetic mechanisms require further investigation. In this study, we compared DNA methylation and gene expression signatures between two dairy cattle populations falling in the high- and low-variant tails of the distribution of milk cortisol concentration (MC), a neuroendocrine marker of stress in dairy cows. Reduced Representation Bisulfite Sequencing was used to obtain a methylation map from blood samples of these animals. The high and low groups exhibited similar amounts of methylated CpGs, while we found differences among non-CpG sites. Significant methylation changes were detected in 248 genes. We also identified significant fold differences in the expression of 324 genes. KEGG and Gene Ontology (GO) analysis showed that genes of both groups act together in several pathways, such as nervous system activity, immune regulatory functions and glucocorticoid metabolism. These preliminary results suggest that, in livestock, cortisol secretion could act as a trigger for epigenetic regulation and that peripheral changes in methylation can provide an insight into central nervous system functions.

Differential expression of miRNAs in milk exosomes of cows subjected to group relocation

This study examined microRNA (miRNAs) expression and regulatory patterns from milk exosomes of cows experienced group relocation, a common husbandry practice during the lactation period and used as a spontaneous model of stress. Total RNA from milk exosome samples was collected from 3 cows that showed an increased milk cortisol (HRC) after relocation (T2 vs T1) and 3 cows that did not show cortisol increase (LRC). A total of 69 known miRNAs were identified. Thirteen miRNAs were consistently down-regulated at T2 in comparison to T1, such as miR-2904-1, miR-142, miR-2284x and miR-30b-3p. Only two miRNAs, miR-2284z and miR-146a were significantly different between LRC and HRC group. Functional enrichment analyses highlighted that glucocorticoid receptor signaling and neurotrophic factor mediated TRK receptor signaling were among the biological pathways affected by differentially expressed miRNA target genes. Mir-135a-5p and miR-320a were involved in both biological pathways. miR-142-5p, miR-142-3p, miR-30b-5p and miR-320a shared the same target genes belonging to the RAS superfamily of small GTP-binding proteins (RAC1, RAP1A and RASA1), involved in neurotrophin-mediated cell survival. MiR-142, miR-135 and miR-320a in milk exosomes were the most responsive to group relocation of cows.

Pharmacokinetics and Bioavailability of the GnRH Analogs in the Form of Solution and Zn2+-Suspension After Single Subcutaneous Injection in Female Rats

BACKGROUND AND OBJECTIVES

Although many synthetic gonadoliberin analogs have been developed, only a few of them, including buserelin, were introduced into clinical practice. Dalarelin, which differs from buserelin by just one aminoacid in the position 6 (D-Ala), is not widely used so far. Gonadotropin-releasing hormone (GnRH) analogs are used to treat many different illnesses and are available in different forms like solution for injection, nasal spray, microspheres, etc. Unfortunately, none of the above drug formulations can release the hormones for 24 h. We assumed that classical suspension could solve this problem.

METHODS

Two sets of experiments were performed. In the first one, buserelin and dalarelin were injected into mature female rats in two forms: suspension, in which the analogs are bounded by Zn²⁺ ions and solution. The pharmacokinetic parameters and bioavailability of the analogs were calculated, based on their concentration in the plasma measured by high-performance liquid chromatography method (HPLC). In the second experiment, the hormones in two different forms were injected into superovulated immature female rats and then the concentration of Luteinizing hormone (LH), Follicle-stimulating hormone (FSH) and 17β-estradiol in the serum was measured by radioimmunological method.

RESULTS

The Extent of Biological Availability (EBA), calculated on the base of AUC_0-∞, showed that in the form of solution buserelin and dalarelin display, respectively, only 13 and 8 % of biological availability of their suspension counterparts. Comparing both analogs, the EBA of dalarelin was half (53 %) that of buserelin delivered in the form of solution and 83 % when they were delivered in the form of suspension. The injection of buserelin or dalarelin, in the form of solution or suspension, into superovulated female rats increased LH, FSH and estradiol concentration in the serum. However, after injection of the analogs in the form of suspension, the high concentration of LH and FSH in the serum persisted longer.

CONCLUSION

Performed studies indicate that GnRH analogs in the form of suspension have higher bioavailability than their solution counterparts. It influences the effects of their action, especially in relation to LH and FSH.

Milk cortisol response to group relocation in lactating cows

The aim of the study reported in this Research Communication was to analyse the variations of milk cortisol concentrations in response to the relocation of dairy cows between production groups. Milk cortisol measured during 3 consecutive days did not vary significantly in cows without environmental perturbation. However, relocation of cows caused a significant increase of cortisol in milk starting from the first milking after the group change. This suggests that cortisol in milk can be a suitable biomarker to assess the HPA response of dairy cows to a short/medium-term environmental challenge.

Release of β-endorphin, adrenocorticotropic hormone and cortisol in response to machine milking of dairy cows

Aim:

The present study was undertaken with the objective to obtain insight into the dynamics of the release of β-endorphin, adrenocorticotrophic hormone (ACTH) and cortisol in response to machine milking in dairy cows.

Materials and Methods:

A total of 10 healthy multiparous lactating Italian Friesian dairy cows were used in the study. Animals were at the 4^th-5^th month of pregnancy and were submitted to machine milking 2 times daily. Blood samples were collected in the morning: In baseline conditions, immediately before milking and after milking; and in the early afternoon: In baseline conditions, before milking and after milking, for 2 consecutive days. Endocrine variables were measured in duplicate, using a commercial radioimmunoassay for circulating β-endorphin and ACTH concentrations and a competitive enzyme-linked immunoassay for cortisol concentration.

Results:

Data obtained showed a similar biphasic cortisol secretion of lactating dairy cows, with a significant increase of cortisol concentration after morning machine milking, at both the 1^st and the 2^nd day (p<0.05), and a decrease after afternoon machine milking at the 2^nd day (p<0.01). One-way RM ANOVA showed significant effects of the machine milking on the cortisol changes, at both morning (f=22.96; p<0.001) and afternoon (f=15.10; p<0.01) milking, respectively. Two-way RM ANOVA showed a significant interaction between cortisol changes at the 1^st and the 2^nd day (f=7.94; p<0.0002), and between the sampling times (f=6.09; p<0.001). Conversely, no significant effects of the machine milking were observed on β-endorphin and ACTH changes, but only a moderate positive correlation (r=0.94; p<0.06) after milking stimuli.

Conclusions:

A wide range of cortisol concentrations reported in this study showed the complex dynamic patterns of the homeostatic mechanisms involved during machine milking in dairy cows, suggesting that β-endorphin and ACTH were not the main factors that caused the adrenocortical response to milking stimuli.