Induction of follicular recruitment is a common method of treatment in bovine donors before initiation of superstimulatory protocol for transvaginal ultrasound-guided oocyte recovery (TVOR; Bo and Mapletoft 2014 Theriogenology 81, 38–48). Two types of induction are frequently applied: dominant follicle reduction (DFR) performed on Day −6 before TVOR, or 2 injections of gonadotrophin releasing hormone (GnRH), 100 μg each, on Day −6 and −13 before TVOR. The objective of this study is to compare the efficacy of DFR v. 2 GnRH injections for inducing follicular recruitment before TVOR in cattle. Dominant follicle reduction is the mechanical aspiration of follicles >5 mm and is a reliable method of initiating follicular recruitment (Blondin 2012 IETS Innovation Workshop 1, St Augustine, FL, USA). This procedure also allows the practitioner to evaluate donors before beginning any treatments. For several reasons (expense, time, and logistics), DFR may be impractical, making a double GnRH regimen appealing. Administering 2 doses of GnRH is simpler but is not considered as reliable; reported ovulation in response to GnRH are ~40% and 60% in heifers and cows, respectively. The donor populations in this study consist of cows and heifers privately owned by farms in the northeastern United States. Donors received an average of 14 to 15 mL (280–300 mg) Folltropin total, split between 6 injections given every 12 h. Cows averaged a 43-h coasting period (time of the last FSH injection to TVOR), and heifers averaged a 31-h coasting period. Oocytes were collected March 2015 to June 2016 by the same practitioner using the same equipment under the same procedure at 2 ovum pickup locations, and submitted to our partnering IVF laboratory, Boviteq USA (Madison, WI, USA). Comparing DFR to 2 doses of GnRH in Table 1, there was no statistically significant difference in total follicles aspirated, total transferable embryos produced or blast rate by either t-test or non-parametric Wilcoxon rank-sum test (P > 0.05). The use of 2 doses of GnRH is an acceptable method for the induction of follicular recruitment before TVOR. Additional statistical models are currently being applied to evaluate which, if any, differences are present in the 2 donor populations. Table 1. Raw data and results¹

Follicle data	N	1–4 mm	5–6 mm	7–10 mm	11–15 mm	>15 mm	Avg Total Foll
GnRH × 2	81
Avg/session		1.5	3.0	13.9	5.0	1.2	21.4
DFR	110
Avg/session		1.5	3.2	12.0	4.6	0.9	19.8
COC data	N	0 cumulus	1–2 Layer	3+ Layer	Deg	Avg Total COC	COC RR
GnRH × 2	81
Avg/session		3.1	5.1	8.1	3.3	15.89	73.3%
DFR	110
Avg/session		3.5	5.9	5.4	2.2	12.71	64.2%
Embryo data	N	Grade 1	Grade 2	Grade 3	Total TE	TE Rate
GnRH × 2	81
Avg/session		4.2	3.7	1.9	6.4	43.3%
DFR	110
Avg/session		3.2	2.1	0.8	5.5	43.9%

¹Avg = average; Foll = follicles.