189 Efficacy of equine chorionic gonadotrophin-like treatment on follicular dynamics and pregnancy rate in Nelore cows submitted to fixed-time AI
L. Angelo de Abreu A , L. Cutaia B , S. Perez Wallace B , T. Santos Resende C , A. Luiz Mancini Carreira D , B. de Sa Cunha E , A. Victoria Goncalves de Sousa E , L. Alves da Silva A , B. Lima Chechin Catussi A and P. Sampaio Baruselli AA Animal Reproduction Department, University of Sao Paulo, Sao Paulo, SP, Brazil
B Syntex, Buenos Aires, Argentina
C Reprobr Pecuaria Inteligente, Santana do Araguaia, PA, Brazil
D Bos Servicos Veterinarios, Araguaina, TO, Brazil
E Universidade Federal do Tocantins, Araguaina, TO, Brazil
Reproduction, Fertility and Development 35(2) 222-222 https://doi.org/10.1071/RDv35n2Ab189
Published: 5 December 2022
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
The present study evaluated the effect of equine chorionic gonadotrophin (ECG)-like glycoprotein produced by recombinant technology (eCG-like) treatment on the follicular dynamics and pregnancy rate of Nelore cows submitted to fixed-time AI (FTAI). A total of 1,928 suckled cows with an average bodyweight (BW) of 356.0 ± 2.9 kg and body condition score (BCS) of 2.4 ± 0.02 (1–5 point scale) from five commercial farms in Brazil were used. At random days of the oestrous cycle (D0), all cows received one intravaginal device of P4 (P4d; CIDR®, Zoetis) followed by the administration of 2 mg of oestradiol benzoate (Gonadiol®, Zoetis, i.m). On D8, the P4d was removed, and animals were homogenously distributed (BW, BCS) to one of the treatments: (1) Control: cows without eCG treatment at the P4 device removal (D8); (2) Conventional eCG: cows treated with 300 IU of conventional eCG (Novormon®, Zoetis, i.m) at D8; or (3) eCG-like: cows treated with 300 IU of eCG-like (PCT/EP2019/073277; Syntex©, i.m) at D8. All animals received 25 mg of PGF2-α (Lutalyse®, Zoetis, Brazil; i.m) and 1 mg of oestradiol cypionate (ECP®, Zoetis, Brazil; i.m) concomitant with P4d removal. At the same time, animals were painted with chalk on their tailheads, and the removal of chalk on the day of FTAI was used as an indication of oestrus. The FTAI was performed 48 h after P4d withdrawal. A subset of animals (n = 271) was evaluated by US (Mindray®, DP-2200) on day of P4d withdrawal (D8), at FTAI (D10) and at the beginning of subsequent diestrus (D17). The following variables were evaluated: diameter of the largest follicle (DLF; mm ± s.e.M), daily growth rate follicle (DGRF; mm/day), ovulation rate (OVR), oestrus detection rate (EDR), and pregnancy rate at FTAI (P/AI). Statistical analyses were performed using PROC GLIMMIX of SAS 9.4. The DLF was greater (P = 0.008) in the eCG-like group (11.0 ± 0.2 mm) than in the control group (9.7 ± 0.2 mm); however, no difference was observed between conventional eCG (10.2 ± 0.2 mm) and eCG-like. Treatment with eCG-like increased (P < 0.0001) the DGRF (1.41 ± 0.10 mm/day) compared with control (0.80 ± 0.09 mm/day) and conventional eCG (1.05 ± 0.08 mm/day) groups. The OVR (presence of CL on D17) was higher (P = 0.07) in the eCG-like (51.4%; 55/107) and conventional eCG groups (46.8%; 51/109) than in the control group (37.0%; 20/55). The P/AI was greater (P < 0.0001) in eCG-like (39.0%; 293/758) and conventional eCG groups (36.0%; 269/751) than in the control group (23.0%; 95/419). No effect of treatment (P = 0.53) was observed for EDR (Control = 84.0% [236/281] vs Conventional eCG = 85.8% [418/487] vs eCG-like = 86.8% [435/501]). In conclusion, eCG-like glycoprotein produced by recombinant technology improved the diameter of the largest follicle at FTAI, the daily growth follicle, the ovulation rate, and the pregnancy rate at FTAI. No differences were observed on reproductive efficiency between the conventional eCG and the eCG-like groups.
