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Negative energy balance (NEB) caused by restricted feed intake leads to body condition loss (BCS), increased metabolic stress and reduced fertility in dairy cows. Propylene glycol (PG) is a precursor of ruminal propionate for gluconeogenesis used to increase metabolic adaptation to the early postpartum period. The aim of this study was to determine the effects of daily drenching of PG during the fixed‐time artificial insemination (FTAI) protocol on beta‐hydroxybutyric acid (BHBA), glucose, adiponectin, insulin‐like growth factor‐1 (IGF1) concentrations, follicle size and pregnancy rate in dairy cows. Cows (n = 148) were randomly divided into two groups and received either 300 mL of PG (PG‐OVS, n = 76) or 300 mL of water (CON‐OVS, n = 72) each day of the Ovsynch protocol (GnRH‐7 days‐PGF2α‐56 hours‐GnRH‐16‐18‐hour FTAI) between days 57 ± 3 to 67 ± 3 postpartum for the first service. Body condition scores (14 days before expected calving, at calving, on days 21 and 42 postpartum) were recorded. Blood samples were collected days 7 ± 3, 21 ± 3 postpartum, at the beginning of the Ovsynch (days 57 ± 3) and at the time of FTAI (days 67 ± 3) for measurements of BHBA, glucose, adiponectin and IGF1 concentrations. Ultrasonographic examinations were done to measure follicle size at the beginning of Ovsynch and FTAI and to determine pregnancy on days 30 and 60 following FTAI. There were no differences (p >.05) in glucose, adiponectin and IGF1 concentrations between the groups during the study. Although there was no difference (p >.05) in BHBA concentrations on postpartum day 7 ± 3, 21 ± 3 and 57 ± 3 between the groups, BHBA concentrations at the time of insemination was lower (p <.05) in the PG‐OVS group (0.72 ± 0.03 mmol/L) than in the CON‐OVS group (0.81 ± 0.03 mmol/L). Follicle sizes at the beginning of Ovsynch (PG‐OVS, 14.5 ± 0.48 mm; CON‐OVS, 14.3 ± 0.59 mm) and FTAI (PG‐OVS, 17.8 ± 0.52 mm; CON‐OVS, 17.7 ± 0.42 mm) were not different (p <.05). Pregnancy rate of the cows in the PG‐OVS group (46.1%, 35/76) was higher (p =.05) than in the CON‐OVS group (30.6%, 22/72) on day 30 following FTAI. In conclusion, decreasing serum BHBA concentrations at the time of FTAI by means of daily drenching of PG during the Ovsynch protocol, increased the pregnancy rate at first service in lactating dairy cows. On the other hand, blood glucose was not related with pregnancy rates in our study, probably as a result of our sampling time and more rapid fluctuations of blood glucose concentrations when compared to BHBA. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the ovulatory response and reproductive performance after Ovsynch protocol in noncyclic dairy cows during the warm (n = 43) and cool seasons (n = 70). Noncyclic cows (n=113) received Ovsynch protocol; GnRH1 (d 0); PGF2α (d 7); GnRH2 (d 9); FTAI (d 10). Ultrasonographic examinations were performed to determine the preovulatory follicle size (d 0, d 10) and ovulatory response to the GnRH1 (d 7) and GnRH2 (d 17). Follicle size at the onset of Ovsynch was not different in cool season (20.8 ± 0.9 mm) compared to that in warm season (19.1 ± 1.1 mm, P > 0.05). The percentage of small-sized follicles at the onset of Ovsynch was higher (P < 0.05) in warm season (37.2%) than cool season (18.6%). However, follicle size at FTAI was similar (P > 0.05) between warm (15.3 ± 0.3 mm) and cool (15.8 ± 0.3) seasons. Ovulatory response to the GnRH1 and the GnRH2 of Ovsynch were not different during the warm (90.7%, 83.7%) and cool seasons (81.4%, 87.1%), respectively (P > 0.05). Pregnancy rate was also similar (P > 0.05) during the warm (34.9%) and cool seasons (35.7%). Cows that had large-sized follicles at the onset of Ovsynch had a tendency (P = 0.08) for lower pregnancy rate in warm season (12.5%) compared to cool season (52.6%). It was concluded that season did not affect the ovulatory response to the first GnRH and pregnancy rate in noncyclic dairy cows that were synchronized with Ovsynch. [ABSTRACT FROM AUTHOR]

Contents: The objective was to compare pregnancy per artificial insemination (P/AI) with conventional (CS) or sex‐sorted semen (SS) in dairy cows subjected to one of the three timed AI protocols. Cows (n = 356) were randomly assigned to synchronization with Ovsynch (OVS), Presynch–Ovsynch (PO) or Double‐Ovsynch (DO) and inseminated on Day 77 ± 3 postpartum with either frozen‐thawed SS (n = 182) or CS (n = 184) of the same bull. More cows were cyclic at the beginning of breeding Ovsynch increased (p < 0.01) with presynchronization and it was greater for DO than PO (OVS = 78.5%, PO = 85.1%, DO = 95.6%). Overall, P/AI for SS and CS increased with presynchronization (p < 0.05) on Days 31 (OVS = 35.5%, PO = 47.1%, DO = 48.3%) and 62 (OVS = 30.1%, PO = 43.8%, DO = 43.9%). Regardless of synchronization treatments, insemination with SS reduced P/AI (p < 0.02) on Days 31 (38.1% vs. 50.6%) and 62 (34.5% vs. 45.6%) compared with CS. No interaction was observed between synchronization treatment and type of semen for P/AI, although in cows receiving CS, P/AI was numerically greatest for PO (OVS = 42.0%, PO = 59.3%, DO = 49.0%), and in cows receiving SS, it was numerically greatest for those inseminated following DO (OVS = 27.9%, PO = 35.5%, DO = 47.6%). Thus, presynchronization improved P/AI in cows inseminated with sex‐sorted or conventional semen. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the effects of the follicle stimulating hormone (FSH) supplemented in the Ovsynch protocol on pregnancy per timed artificial insemination (P/TAI) in cyclic dairy cows. All cows (n = 383) included in the study received the Ovsynch protocol. The cows in FSH3 (n = 92), FSH4 (n = 88), and FSH3&4 (n = 91) were administered 20 mg FSH on day 3, or day 4, or both on days 3 and 4 of the protocol, respectively, whereas the control group (n = 112) did not receive any FSH treatment. The mean follicle number at TAI and ovulation number after TAI were similar among the FSH groups. However, the mean follicular size was smaller (~14.9 mm, P = 0.02) in FSH4 compared to the other groups (~15.9 mm). Pregnancy/TAI of the FSH4 group on day 31 (59.1%) and day 62 (53.4%) was higher than those of other groups on day 31 (45.5% in control, 45.7% in FSH3, and 46.2% in FSH3&4) and day 62 (42.9% in control, 43.5% in FSH3, and 40.7% in FSH3&4), but the difference was non-significant. Likewise, FSH4 (62.7%) had more (P = 0.05) P/TAI than the other groups (48.6% in control, 47.7% in FSH3, and 49.4% in FSH3&4) in synchronized cows. The cows which responded to the first gonadotropinreleasing hormone (GnRH) of Ovsynch in the FSH4 group (64.8%) had higher (P < 0.02) P/AI rate than the responding control cows (44.6%). We concluded that application of FSH on day 4 in cyclic cows which were responsive to the Ovsynch protocol can yield higher pregnancy rates, but more studies are needed to better demonstrate this potential effect. [ABSTRACT FROM AUTHOR]

This study focused on determining the success of inducing endogenous progesterone source (by formation of accessory corpus luteum) by human chorionic gonadotropin (hCG) administration on day 4 post timed artificial insemination (TAI) and on evaluating the effect of the day of hCG administration (day 4 or 5 post TAI) on pregnancy rates in repeat breeder cows according to their responses to hCG administrations. Non-pregnant cyclic lactating Holstein dairy cows with more than three services despite no clinical reproductive abnormalities were enrolled in the study. All cows (n = 192) received the Ovsynch protocol (GnRH-7d-PGF2α-56h-GnRH-16/18h-TAI) and hCG administration (1500 IU, i.m.) was performed in group hCG4 (n = 64) on day 4 and in group hCG5 (n = 68) on day 5 post TAI. The control group (CON, n = 60) did not receive any hCG treatment. The responses (ovulation rate) to hCG (~64%) were similar on days 4 and 5 post TAI. Pregnancy per AI (P/AI) at 31 days was similar among the groups (48.3% in CON, 48.4% in hCG4, and 42.6% in hCG5). Regardless of the day of the treatment (hCG4 + hCG5), the cows had an ovulatory response to hCG (54.1%), and a greater P/AI (P = 0.007) at 31 days than those without a response (29.8%). The administration of hCG on either day 4 or 5 post TAI did not increase overall pregnancy rates, however, the ovulatory response to the post TAI hCG administration on day 4 improved fertility in repeat breeder cows. Further studies are needed with a larger number of animals to reveal this potentiallly beneficial effect. [ABSTRACT FROM AUTHOR]