This study aimed to evaluate embryo yield in Holstein heifers superovulated with a single injection of recombinant, long-acting human follicle-stimulating hormone (rFSH) vs. multiple injections of pituitary-derived follicle-stimulating hormone (FSH). In experiment 1, heifers were assigned randomly to one of four experimental groups: Control (280 mg of pituitary-derived FSH; six injections of 40 mg and two injections of 20 mg, each ~12 h apart, n = 16); rFSH1 (50 µg of FSH analog protein, n = 16); rFSH2 (75 µg of FSH analog protein, n = 16); or rFSH3 (100 µg of FSH analog protein, n = 16). The rFSH was administered as a single injection. Estrous cycles were presynchronized with gonadorelin acetate (GnRH) and an intravaginal progesterone insert (CIDR) on day 8, followed by cloprostenol sodium (PGF2α) on day 3 and day 2 with removal of the CIDR, and GnRH on day 0. On day 5, ovarian follicles ≥ 5 mm in diameter were ablated by transvaginal ultrasound-guided aspiration. On day 6.5, the heifers received a CIDR and the first injection of either rFSH or pituitary-derived FSH. On day 9, the heifers received two injections of PGF2α, 12 h apart. On day 10.5, the CIDR was removed, and on day 11, the heifers received a GnRH injection. Heifers were AI-inseminated 12- and 24-h post-GnRH injection, and uterine contents were flushed transcervically on day 18 (7 d after the GnRH injection). Ovarian follicles ≥ 5 mm and corpora lutea (CL) were counted via ultrasound on days 5, 9, and 18. In experiment 1, group did not affect (P = 0.52) the number of follicles ≥ 5 mm (Control = 15.9 ± 1.2; rFSH1 = 17.5 ± 1.3; rFSH2 = 17.1 ± 1.3; rFHS 3 = 18.6 ± 1.4 follicles) or the number of CL (P = 0.96) on day 9 (Control = 1.1 ± 0.3; rFSH1 = 1.1 ± 0.3; rFSH2 = 1.1 ± 0.3; rFSH3 = 0.9 ± 0.2). Furthermore, there was no effect (P = 0.28) of rFSH dose on freezable embryos (grade 1 and 2 embryos) collected on day 18 (Control = 4.7 ± 1.1; rFSH1 = 4.7 ± 1.2; rFSH2 = 4.4 ± 1.1; rFSH3 = 2.6 ± 0.7 embryos). In experiment 2, Control (n = 8) and rFSH1 (n = 16) groups were repeated in three replicates using the same protocols as experiment 1. Consequently, Results showed that rFSH produced fewer total number of ova/embryos (Control = 9.9 ± 1.5 vs. rFHS1 = 5.9 ± 0.9, P = 0.04) and fewer freezable embryos (Control = 5.3 ± 1.0 vs. rFSH1 = 1.4 ± 0.3, P < 0.01). In conclusion, the single rFSH injection effectively induced superovulation; however, its repeated use reduced embryo production.
Keywords: Holstein heifer; follicle-stimulating hormone; superovulation.
This study explored a novel recombinant hormone to produce embryos in Holstein heifers, using a single injection of a long-acting human follicle-stimulating hormone (rFSH) compared with the traditional method of multiple injections of pituitary-derived follicle-stimulating hormone (FSH). We compared both hormones multiple times to evaluate the number of embryos produced. Our results showed that a single injection of rFSH was as effective as multiple injections of FSH in terms of recovered ova/embryos. However, when the single injection of rFSH was used repeatedly in the second part of the study, it resulted in a smaller total number of ova/embryos and freezable embryos. In conclusion, although a single injection of rFSH can effectively stimulate the ovaries, its repeated use may reduce the number of embryos produced. This finding is crucial for advancing embryo production techniques in dairy cattle.
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