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Made available in DSpace on 2022-04-29T08:46:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-15 In cattle, uterine luminal fluid (ULF) is the main source of molecules that support embryo development and survival during the peri-implantation period. Our overarching hypothesis is that peri-estrus changes in uterine function, including ULF accumulation and absorption, are uneven among individuals, and affect ULF composition and fertility. Our objectives were (1) to characterize temporal and spatial changes in ULF volume, endometrial and luteal blood perfusion, endometrial and luteal size, and circulating progesterone concentrations during the peri-estrus period in beef heifers and (2) to associate such changes with the metabolite composition in the ULF, 4 days after estrus (d 0). Fourteen Bos indicus heifer that presented a PGF2α responsive CL received 500 μg PGF2α analog i.m. and were examined daily by rectal B-mode and pulse-wave color-Doppler ultrasonography until the fifth day after estrus (d 5). The composition of the ULF was analyzed by targeted mass spectrometry on d 4. Multivariate analyses clustered heifers according to ovarian, uterine, and hormonal variables in clusters A (n = 5) and B (n = 8 heifers). Concentrations of Pro, Ala, Leu, Gly, Val, Lys, Ile, Phe, Asp, Orn, Tyr, Arg, Trp, Suc, Cit, ADMA, the sum of essential Amino Acids (AA), sum of nonessential AA, sum of aromatic AA, and total AA were greater in cluster A (FDR ≤ 0.05). ULF volume dynamics and uterine, ovarian, and hormonal variables during the peri-estrus period presented a concerted variation among heifers within clusters, which was associated with the ULF composition 4 days after estrus. Department of Animal Sciences University of Florida FL Department of Animal Reproduction School of Veterinary Medicine and Animal Sciences University of São Paulo Department of Surgery Division of Urology Federal University of São Paulo School of Veterinary Medicine São Paulo State University School of Veterinary Medicine São Paulo State University

We aimed to compare the effects of use of 1 or 2 mg estradiol benzoate (EB) associated with an intravaginal progesterone (P4) device for resynchronization of ovulation 14 days after timed-AI (TAI) in suckled beef cows. Nelore cows were submitted to a TAI (D0) and on D14, received an intravaginal P4 device and were randomly assigned to EB-1 group [n = 516] or EB-2 group [n = 510], which that received 1 or 2 mg EB, respectively. Also, cows had the ovaries scanned by ultrasound to detect an active CL on D14. On D22, devices were removed and structural luteolysis was detected by color-Doppler ultrasonography. In cows which underwent luteolysis, the resynchronization protocol was continued and they were submitted to second TAI on D24. Pregnancy diagnosis was performed 30-35 days after first or second TAI. A subgroup [n = 18-19/group] was submitted to daily ovarian ultrasound scanning from D14 to D22. Proportion of cows with an active CL on D14 did not differ (P 0.1) between EB-1 and EB-2 groups. The proportion of cows with an active CL on D22 and pregnancy per AI (P/AI) at first TAI were greater (P ≤ 0.05) in EB-1 (55% and 51%) than in EB-2 group (48% and 42%). The P/AI at second TAI did not differ (P 0.1) between EB-1 (47% [106/227]) and EB-2 group (42% [110/259]). Cumulative pregnancy rate was greater in EB-1 (73% [370/508]) than in EB-2 group (64% [322/502]). No difference (P 0.1) was observed in the proportion of non-pregnant cows with a synchronized follicular wave emergence between EB-1 and EB-2 groups. In conclusion, treatment with either 1 or 2 mg EB associated with an intravaginal P4 device at D14 after TAI are efficient to synchronize a new follicular wave emergence. The decreased P/AI from first TAI observed in the group of cows receiving 2 mg indicates that this dose is not recommended for use in resynchronization programs initiated 14 days after TAI. The use of 1 mg EB associated with a P4 device provides an elevated cumulative pregnancy rate after two TAIs with an interval of 24 days.