125 The effects of human chorionic gonadotrophin administered 7 days after induced oestrus on original (ovulatory) and induced (accessory) corpora lutea and on pregnancy rates in seasonally anovular dairy goats
J. N. D. Rodrigues A , J. D. Guimarães A , M. E. F. Oliveira B F , J. H. Dias A , G. B. Vergani B , M. A. P. Sousa C , R. Bastos D , B. Ahmadi E , P. M. Bartlewski E and F. F. Fonseca FA Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil
B Universidade Estadual Paulista, Jaboticabal, São Paulo, Brazil
C Universidade Federal Rural da Amazônia, Belém, Pará, Brazil
D Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Rio de Janeiro, Brazil
E University of Guelph, Guelph, ON, Canada
F Embrapa Caprinos e Ovinos, Sobral, Ceará, Brazil
Reproduction, Fertility and Development 34(2) 300-300 https://doi.org/10.1071/RDv34n2Ab125
Published: 6 December 2021
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
Inadequate production of progesterone (P4) is a cause of 30 to 40% of embryonic deaths. Luteal inadequacy occurs mainly in animals bred during seasonal anestrus. Therefore, additional strategies must be used to boost luteal function after oestrus induction protocols in seasonally anovular females. One of the most effective methods to increase P4 levels is administration of human chorionic gonadotrophin (hCG) to induce the formation of accessory corpora lutea (aCL). Two experiments were carried out to evaluate the luteotropic (Exp. 1) and progestational effects (Exp. 2) of hCG administrated 7 days after the onset of induced oestrus in seasonally anovular Alpine (A) and Saanen (S) goats. In both experiments, intravaginal sponges containing 60 mg of medroxyprogesterone acetate were inserted for 6 days, and 200 IU of equine chorionic gonadotrophin (eCG) and 30 μg of D-cloprostenol were administered IM 24 h before sponge removal. In Exp. 2, all goats underwent AI on Day 1 (Day 0 = onset of behavioural oestrus). On Day 7, all goats were randomly divided into two groups: G-hCG does received 300 IU of hCG IM (Exp. 1: n = 8 A; Exp. 2: n = 75 A + S), and G-Control (Exp. 1: n = 8 A; Exp. 2: n = 70 A + S). Transrectal ovarian ultrasonography and blood collection were done on Days 7, 10, 13, 17, and 21 (Exp. 1), and ultrasonographic pregnancy detection on Day 60 (Exp. 2). All single time-point observations were compared using Student’s t-test, and serial data were analysed using repeated-measures ANOVA in SigmaPlot (Systant Software). Percentages were compared by chi-squared test (Brandt-Snedecor formula). Correlational analyses utilised the Pearson product–moment correlation. Oestrus and ovulations occurred in five of eight (62.5%) does allotted to G-hCG and in seven of eight (87.5%) control animals (P > 0.05). Total luteal area and mean cross-sectional area of ovulatory corpora lutea (oCL) increased (P < 0.05) on Day 10 in G-hCG and remained greater (P < 0.05) compared with thtat of G-Controls until Day 21. Accessory CL were observed in all five G-hCG does from Day 13 onward. Total and high-velocity colour Doppler area was greater (P < 0.05) for oCL of G-hCG does on Day 13 but mean Doppler area in G-Control does exceeded (P < 0.05) that of hCG-treated animals on Day 21. Circulating P4 concentrations were greater (P < 0.05) in G-hCG compared with control goats from Day 13 to Day 21 and were related directly to total luteal and oCL area for the duration of the present study in all does. The pregnancy rate was higher (P < 0.05) in G-hCG than in respective controls (70.3% vs. 47.8%). In conclusion, administration of 300 IU of hCG 7 days after the beginning of induced oestrus in dairy goats resulted in formation of aCL and had a hypertrophic effect on oCL. Consequently, serum P4 concentrations were greater in hCG-treated does during the period of the maternal recognition of pregnancy. A single dose of hCG significantly increased the pregnancy rate in seasonally anovular oestrus-induced dairy goats.
