Effect of the length of FSH treatment (4d vs 7d) on the superovulatory response of lactaing Holstein cows

The aim of the study was to evaluate whether long-term treatment with FSH improves superovulatory response of dairy cows.. Holstein cows (n = 89) producing on average 40.2 ± 5.2 kg/day were randomized to two superovulation protocols at 63 ± 3d DIM, as follows: 1) Short protocol (FSH4d): D-1 = Follicle ablation, D1 to D4 = CIDR insertion and 400 mg of FSH (Folltropin®) applied AM/PM, D3 and D4 AM = PGF2a and CIDR removal together with 2nd PGF2a treatment and 12h before last FSH, D5 AM = GnRH and AI 12 and 24h after GnRH with conventional non-sexed semen from same sire and a single ejaculate. The long protocol (FSH7d) followed a similar sequence of treatments but the 400 mg dose of FSH was extended over 7 days instead of 4. All cows were inseminated by the same AI technician and nonsurgical collection of ova/embryos took place 7 days after GnRH by one of three technicians. Embryo grading was performed by a single technician (blindly) according to IETS guidelines. Data was analyzed by the Glimmix procedure of SAS (version 9.3), the Poisson distribution was assumed for most embryo-related variables and cow was interpreted as the experimental unit. Results for FSH4d and FSH7d were, respectively: total number of CL (FSH4d = 12.0 ± 0.8 vs FSH7d = 12.9 ± 0.8; P=0.22); total structures (FSH4d = 4.8 ± 0.5 vs FSH7d = 4.5 ± 0.6; P=0.49); fertilization rate (FSH4d = 83.8 ± 5.0 vs FSH7d = 92.3 ± 4.0; P=0.18); number of transferable embryos (FSH4d = 1.8 ± 0.4 vs FSH7d = 2.4 ± 0.6; P=0.43); number of freezable embryos (FSH4d = 1.3 ± 0.3 vs FSH7d = 2.1 ± 0.5; P=0.43); percent of degenerated embryos out of fertilized (FSH4d = 41.4 ± 6.2 vs FSH7d = 43.6 ± 6.4; P=0.79). These results suggest that the 7-day (long) FSH protocol failed to improve embryo production in high producing Holstein cows.