Abstract
The precise role of the endocannabinoid system (ECS) at the pregnancy of dairy cows remains elusive, therefore this study was designed to compare different components of the ECS between pregnant cows and those that had experienced early embryonic losses at the mRNA levels. Holstein cows (n=130, average parity 3.3, body condition score of 3.1 at calving) were selected for the study on 10th d postpartum. Cows were subjected to GnRH-based ovulation synchronization protocol for timed artificial insemination (TAI). Blood samples were collected on 16th d after calving to determine interferon-stimulated gene-15 (ISG-15) relative mRNA expression. Prediction of pregnancy status on d 16 after TAI was determined by determining interferon-stimulated gene- 15 mRNA expression relative to standard genes (ß actin and GAPDH). Results showed CNR1, N-acylphosphatidylethanolamine-specific phospholipase D (NAPEPLD), fatty acid amide hydrolase (FAAH) are differentially expressed in the uterus of cows with early embryonic loss (n=30) when compared to the expression in confirming pregnancies (n= 3). Expression of CNR1 and NAPEPLD were greater (3.56 and 4.72 fold respectively), while FAAH expression (6.75 fold) was lower in cows with early embryonic loss compared to healthy cows. Expression of mRNA for the other candidate genes, which included monoacylglyceride lipase (MGLL), N-acyl ethanolamine amino hydrolase (NAAA) and diacylglycerol lipase (DAGL) was not differentially expressed between compared groups ofcows. Cows with early embryonic loss had lower serum progesterone and greater prostaglandin F2a metabolite (PGFM) levels compared to healthy ones during first 20 days of pregnancy. Our data confirm for the first time that association between the components of the endocannabinoid system and early embryonic losses in dairy cows exists. We provide evidence that endocannabinoid system is altered in the endometrium of cows of early embryonic loss through increased mRNA expression of CNR1 and synthesis enzyme (NAPEPLD) and decreased mRNA expression of hydrolyzing enzyme (FAAH).