124 Reutilisation of intravaginal progesterone devices during fixed-time artificial insemination with sex-sorted semen in dairy heifers
R. Sala A , V. Absalon-Medina A , T. Reamsnyder A , E. Maldonado A , W. Smith A , V. Fricke A , J. Moreno B and A. Garcia-Guerra CA STgenetics, South Charleston, OH, USA
B STgenetics, Navasota, TX, USA
C Department of Animal Sciences, The Ohio State University, Columbus, OH, USA
Reproduction, Fertility and Development 34(2) 299-300 https://doi.org/10.1071/RDv34n2Ab124
Published: 7 December 2021
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
Reutilisation of progesterone (P4) devices during fixed-time AI (FTAI) protocols is a practical strategy to reduce the overall cost of FTAI programs. In addition, this strategy reduces circulating P4 concentration allowing a relatively greater frequency of LH pulses that in turn increases preovulatory follicle size and, thus, can potentially improve fertility. Therefore, the objective of the present study was to determine the effect of reutilisation of intravaginal P4 devices, during a 5-day CO-Synch protocol for FTAI using sex-sorted semen, on fertility outcomes. A total of 586 dairy heifers with an average age of 16.7 ± 0.1 months were assigned, in a completely randomised design, to receive a new (first use; n = 299) or reused (second use; n = 287) P4 intravaginal device during a 5-day CO-Synch. Briefly, on Day −8, a first use or second use (previously used once for 5 days) controlled internal drug release (CIDR, 1.38 g of P4, Zoetis) was inserted and 200 µg of gonadorelin acetate (gonadotrophin-releasing hormone (GnRH), Gonabreed, Parnell) was administered. Five days later (Day −3), CIDRs were removed and prostaglandin F2α analogue (PGF, 500 µg of cloprostenol sodium, Estroplan, Parnell) was administered twice 24 h apart (Day −3 and Day −2). On Day 0 (72 h after CIDR removal), 100 µg of GnRH was administered, and heifers were artificially inseminated using frozen-thawed female sex-sorted semen (SexedULTRA 4MTM; STgenetics). A subset of heifers (n = 563) received an Estrotec® patch, which was evaluated for signs of oestrus on Day 0. Pregnancy diagnosis was performed using transrectal ultrasonography at 32 and 60 days after FTAI. Data were evaluated using generalised linear mixed models (SAS 9.4; SAS Institute Inc.), with treatment as a fixed effect and AI technician as a random effect. The percentage of heifers expressing oestrus was not different (P = 0.22; Table 1) between heifers synchronised with a first use or second use CIDR. Additionally, pregnancies per AI (P/AI) at Day 32 and Day 60 were not different (P > 0.3) between heifers synchronised with a first or second use CIDR (Table 1). Heifers expressing oestrus had greater (P < 0.01) P/AI than those that did not at Day 32 (48.9%; 247/505 vs. 29.3%; 17/58) and D60 (47.5%; 240/505 vs. 25.9%; 15/58). There was, however, no interaction between treatment and oestrus expression (P > 0.3). Furthermore, pregnancy loss between Day 32 and Day 60 was not different (P = 0.62; Table 1) between treatment groups and was not affected by oestrus expression (P = 0.98). In conclusion, reutilisation of intravaginal P4 devices can be an adequate approach to reduce the cost of FTAI programs with sex-sorted semen in dairy heifers without compromising reproductive performance.
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