Abstract
BackgroundThis study evaluated the impact of hormonal modulation at the onset of proestrus on ovarian response and uterine gene expression of beef cows.MethodsA total of 172 anestrous beef cows were assigned to one of four groups according to the treatment with estradiol cypionate (ECP) and/or equine chorionic gonadotropin (eCG) [CON (n = 43), ECP (n = 43), eCG (n = 44) and ECP + eCG (n = 42)].ResultsECP-treated cows (ECP and ECP + eCG groups) presented greater occurrence of estrus (44.6% vs. 65.4%; P = 0.01) and pregnancy per AI [47.1% vs. 33.3%; P = 0.07], but similar progesterone (P4) concentration at subsequent diestrus than cows not treated with ECP (CON and eCG groups). Nonetheless, eCG-treated cows (eCG and ECP + eCG groups) presented larger follicle at timed AI (12.6 ± 0.3 vs. 13.5 ± 0.3 mm; P = 0.03), greater ovulation rate (96.5% vs. 82.6%; P = 0.008) and greater P4 concentration at d 6 (3.9 ± 0.2 vs. 4.8 ± 0.2 ng/mL; P = 0.001) than cows not treated with eCG (CON and ECP groups). Next, cows with a new corpus luteum 6 d after TAI were submitted to uterine biopsy procedure. Uterine fragments [CON (n = 6), ECP (n = 6)] were analyzed by RNA-Seq and a total of 135 transcripts were differentially expressed between groups (73 genes up-regulated by ECP treatment). Subsequently, uterine samples were analyzed by qPCR (genes associated with cell proliferation). ECP treatment induced greater abundance of PTCH2 (P = 0.07) and COL4A1 (P = 0.02), whereas suppressed EGFR (P = 0.09) expression. Conversely, eCG treatment increased abundance of HB-EGF (P = 0.06), ESR2 (P = 0.09), and ITGB3 (P = 0.05), whereas it reduced transcription of ESR1 (P = 0.05). Collectively, supplementation with ECP or eCG at the onset of proestrous of anestrous beef cows influenced ovarian responses, global and specific endometrial gene expression. ConclusionProestrus estradiol regulate the endometrial transcriptome, particularly stimulating proliferative activity in the endometrium.
Highlights
This study evaluated the impact of hormonal modulation at the onset of proestrus on ovarian response and uterine gene expression of beef cows
There were no interactions between estradiol cypionate (ECP) and equine chorionic gonadotropin (eCG) treatment on response variables, except for the corpus luteum (CL) diameter 6 d after the timed artificial insemination (TAI) (P = 0.06)
Larger CLs were observed in cows treated with eCG, especially in cows not treated with ECP
Summary
This study evaluated the impact of hormonal modulation at the onset of proestrus on ovarian response and uterine gene expression of beef cows. Gene expression of bovine endometrium changes according to the phase of the estrous cycle and is closely controlled by circulating concentrations of estradiol (E2), progesterone (P4) and the expression ratio of their specific receptors [8, 14,15,16,17]. In this regard, proestrus E2 concentration is fundamental in modulation of the uterus for the subsequent luteal phase [8, 14, 18, 19]. It is reasonable to hypothesize that the modulation of E2 concentration during the synchronized proestrus by means of exogenous E2 supplementation could alter the uterine gene expression of suckled anestrous beef cows
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