178 Fixed-time artificial insemination in virgin beef heifers using a seven-day progesterone-based protocol: gonadotrophin-releasing hormone versus oestradiol salts
L. B. Ferré A , B. Aguirregabiria B , N. Cerviño C , R. Bello D , M. Jensen A , C. Fresno E , M. E. Kjelland F G and M. Colazo HA National Institute of Agricultural Technology, Chacra Experimental Integrada Barrow (MDA-INTA), Tres Arroyos, Buenos Aires, Argentina
B Veterinary Consultant, Orense, Buenos Aires, Argentina
C CONICET/INTA, Tres Arroyos, Buenos Aires, Argentina
D National University of Tres de Febrero, Caseros, Buenos Aires, Argentina
E Health Sciences Research Center, Anáhuac University of México, Naucalpan de Juárez, México, México
F Conservation, Genetics & Biotech, LLC, Valley City, North Dakota, USA
G Mayville State University, Mayville, North Dakota, USA
H Livestock Research Section, Alberta Agriculture and Forestry, Edmonton, Alberta, Canada
Reproduction, Fertility and Development 35(2) 216-217 https://doi.org/10.1071/RDv35n2Ab178
Published: 5 December 2022
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
Follicular wave and ovulation synchronisation differ depending on the selection of gonadotrophin-releasing hormone (GnRH) versus oestradiol for fixed-time artificial insemination (FTAI) protocols. The aim of this research was to determine reproduction efficiency of virgin beef heifers using either GnRH or oestradiol salts. Prior to beginning the work, a gynaecological examination was performed by rectal palpation to determine the presence of the corpus luteum and/or follicles larger than 10 mm. Feeding consisted of ad libitum offering of alfalfa and ryegrass, mineral salts, and unrestricted access to water. Virgin Hereford heifers (15–17 months of age) weighing 321.0 ± 13.6 kg with an average body condition score ([BC] on a scale of 1–5) of 3.4 ± 0.4 were used. On Day 0, the animals were randomly divided into two groups, taking into account the weight and BC. All animals received an intravaginal device impregnated with 1 g of progesterone (Laboratorios Allignani Hnos. SRL). Group 1 (oestradiol benzoate [EB] + EC, n = 24) received an i.m. injection of 2 mg of EB and Group 2 (GnRH, n = 24) 10.5 ug of buserelin acetate-GnRH. On Day 7, the device was removed, the tails of all heifers were painted, and 150 ug of D-cloprostenol was administered to all animals. Group 1 also received an i.m. injection of 1 mg of oestradiol cypionate (EC). Right after the device was removed, an ultrasound examination was performed (Aquila 200 Vet, Esaote Pie Medical) to register the presence of the corpus luteum (CL) and/or the larger follicle diameter. The FTAI was performed on Day 9 (50–52 h post device removal). Group 2 received 10.5 ug of GnRH (i.m. injection) at the time of FTAI. A single proven fertile bull was used and FTAI was carried out by a single inseminator. The pregnancy diagnosis was performed 35 days after FTAI by ultrasound. ANOVA was used for comparisons of mean values and Pearson’s chi-squared test was used for proportions (α = 0.05). Results are presented in Table 1. Both 7-day progesterone-based FTAI protocols produced similar results regarding reproductive efficiency in virgin beef heifers although BC tended to affect pregnancy rate (P < 0.05) in virgin Hereford heifers submitted to oestrogens-based FTAI protocols.
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