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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-PGF 2α -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., (© 2023 The Authors. Reproduction in Domestic Animals published by Wiley-VCH GmbH.)

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., (© 2018 Blackwell Verlag GmbH.)

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]