99 Effect of LH contamination in commercial formulations on FSH-induced follicle growth in heifers immunised against gonadotrophin-releasing hormone

In the present study, we compared the response to superstimulation of commercial FSH formulations with different amounts of LH contamination. We used as experimental model Nelore (Bos indicus, n = 10) heifers actively immunised against gonadotrophin-releasing hormone (GnRH). Suppression of follicular growth beyond 4 mm in diameter was obtained after three SC injections of 1 mL of anti-GnRH vaccine (Bopriva, Zoetis), given at 20-day intervals. After 14 days, follicles >2 mm were ablated by ovum pick-up (OPU) and 5 days later (Day 0), the heifers were superstimulated using commercial FSH formulations with either low (Folltropin, Vetoquinol; Foll group; n = 5) or high (Pluset, Biogénesis Bagó; Plus group; n = 5) LH content, respectively. The FSH was injected twice a day, in eight decreasing doses (100 mg in Foll or 200 IU in Plus group). Transvaginal ultrasonography was performed daily, from Days 0 to 4, and the size and number of antral follicles were recorded. At Day 4, both groups were submitted to OPU, the cumulus-oocyte complexes (COC) recovered were graded, and viable COC were sent to an in vitro embryo production (IVEP) laboratory. On Day 11 (7 days after OPU), heifers were re-evaluated, and blood samples were collected for analysis of progesterone (P4) concentrations by radioimmunoassay. Follicle and P4 data were analysed using the Glimmix procedure of SAS (SAS Institute Inc.); viable oocytes and blastocyst rates were compared by the chi-squared method. The results were shown as mean ± s.e.m. or %. There was no change in antral follicle population during superstimulation within groups (P > 0.05). The average follicle size was similar between groups at Day 0 (2.4 ± 0.0 vs. 2.6 ± 0.1 mm in Foll and Plus, respectively; P > 0.05), and in both groups a progressive increase in follicle size was observed from Day 0 to Day 4 (P < 0.0001). However, follicular growth rate was greater in Plus than in Foll (1.5 ± 0.1 vs. 0.8 ± 0.1 mm d⁻¹, respectively; P < 0.0001); resulting in a greater follicle diameter at Day 4 in Plus than in Foll (8.4 ± 0.4 vs. 5.6 ± 0.7 mm, respectively, P < 0.0001). The Foll group yielded fewer viable COC (18.8 ± 4.0 vs. 28.8 ± 3.6; P < 0.05) and fewer COC graded as I or II (33.8% vs. 85.3%; P < 0.05) than the Plus group. Nevertheless, blastocyst rates were similar (40.8 vs. 50.0% in Foll and Plus, respectively; P > 0.05). In both groups, no luteal tissue was detected and P4 concentrations were low (0.09 ± 0.04 vs. 0.22 ± 0.04 ng mL⁻¹ in Foll and Plus, respectively; P > 0.05) at Day 11. In summary, the LH content of commercial FSH formulations affects follicle growth pattern and COC quality in heifers immunised against GnRH. These results suggest that endogenous LH may play an important role during superstimulation when FSH formulations with low LH content are used.

This research was funded by CAPES and Project SEG 30.19.90.006.00.