The aims of this study were to determine the factors that affect follicle size at the time of artificial insemination (AI) and to detect the relationship between ovulatory follicle size at the time of AI and pregnancy rate in dairy cows. A total of 1428 follicle size measurements were obtained from Holstein-Friesian (HF) and Swedish Red (SR) cows that were inseminated with the fixed-timed AI protocols used in this study. Follicle size was affected by breed (P = 0.0001), milk production (P = 0.01), parity (P = 0.05), and season (P = 0.04). Follicle size was greater (P = 0.0001) in the HF (15.55 mm) than the SR cows (14.88 mm). Multiparous cows had larger (P = 0.04) follicles (15.35 mm) than the primiparous cows (15.07 mm). Cows with follicle sizes between 13.5 and 17.5 mm were more likely to be pregnant than cows with other sizes follicles (P < 0.01). Embryonic loss was lower (P < 0.01) in cows with follicle sizes between 13.5 and 16.5 mm. Thus, the follicle size was affected by breed, milk production, parity, and season. Pregnancy and embryonic loss in lactating dairy cows were significantly related to follicle size.

Sex-sorted semen is an innovative technology to sustain a dairy farm economically profitable. Male calves generally have a little economic income in the dairy herds; thus, the use of sex-sorted semen is preferred for increasing the number of female calves which are used as replacement heifers afterwards (Cottle, Wallace,

ContentsThe 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. K E Y W O R D S dairy cow, ovsynch, presynchronization, sex-sorted semen

No abstract

Background: Beta-(β-) carotene, is the precursor to vitamin A, in particular, has some potential benefits on reproduction. The main objective of this study was to investigate the efficacy of β-carotene administration on fertility following either prostaglandin F2 alpha (PGF) induced estrus or Ovsynch protocol in lactating dairy cows.Methods: Cows with at 47±3 postpartum days were divided into two groups: β-carotene group (βC, n=139) was treated with injectable β-carotene while untreated cows served as control (CON, n=227). In both groups, PGF was administered and heatmount detectors were applied at 54±3 days postpartum. Cows detected in estrus after PGF were inseminated. Cows that had not been detected in estrus were divided into two groups 7 days after PGF administration; βC-OVS (n=137) and CON-OVS (n=89). Ovsynch protocol was initiated 4 days after β-carotene administration.Result: The estrus detection rate was similar between the βC and CON groups (P = 0.19). Pregnancy per AI (P/AI) on d 31 was also similar between groups (P = 0.93). In the Ovsynch protocol, ovulation to the first GnRH and ovulatory follicle diameter at the time of insemination did not differ between groups. No difference was observed in P/AI at d 31 (P = 0.13). The results of this study indicated that β-carotene administration had no effect on fertility either PGF induced estrus or Ovsynch protocol in dairy cows.