203 EFFECT OF SUPPLEMENTAL FOLLICLE-STIMULATING HORMONE OR EQUINE CHORIONIC GONADOTROPIN DURING THE PROTOCOL FOR TIMED AI IN HIGH-PRODUCING HOLSTEIN COWS

Abstract

Programs that allow timed AI (TAI) have been used to improve reproductive efficiency in dairy herds; however, in many cases pregnancies per AI (P/AI) during these programs remain suboptimal. In the present experiment, it was hypothesized that treatment with FSH or eCG at the time of the PGF2 treatment of the TAI protocol would increase fertility in dairy cattle. This experiment was performed in June 2008 (winter) and January 2009 (summer) on 2 commercial dairy farms located in southeast Brazil. On a random day of the estrous cycle (Day 0), 694 cows at 196 ± 138 days in milk (DIM) received 2 mg of estradiol benzoate (RICB^®, Tecnopec, São Paulo, Brazil) i.m. and a releasing intravaginal device (P4; Primer^®, Tecnopec), which was removed on Day 8 when 150 μg of PGF (Prolise^®, ARSA, Buenos Aires, Argentina) i.m. were administered. At this time, the cows were stratified by days in milk (DIM), parity, number of insemination, milk production, presence of a CL on Day 0, and body condition score (BCS) and were randomly assigned to 1 of 3 treatments: control (n = 232), consisting of no additional treatment; eCG (n = 232), consisting of 400 IU of eCG (Folligon^®, Intervet, São Paulo, Brazil); and FSH (n = 230), consisting of 20 mg of FSH (Folltropin^®, Bioniche, Belleville, Ontario, Canada). All cows received GnRH (100 μg of gonadorelin; Fertagyl^®, Intervet) and were TAI 56 h after the removal of the device. Pregnancy diagnosis was performed 30 and 60 days after TAI. Also, a subset of animals (n = 89) was submitted to ultrasonographic exams to evaluate the diameter of the ovulatory follicles (ØOF), time to ovulation after P4 removal (TOV), and ovulation rate (OR). Statistical analyses were performed with logistic regression by PROC GLIMMIX of SAS (SAS Institute, Cary, NC, USA). There were no interactions of treatment with DIM, parity, number of insemination, BCS, locomotion score, sire, batch, inseminator, farm, or month; therefore, these variables were removed from the statistical model. The overall P/AI was different between treatments at 30 days after TAI [control = 28.0% (65/232), eCG = 29.7% (69/232), and FSH = 18.7% (43/230); P = 0.01], but not at 60 days [control = 21.6% (50/232), eCG = 24.1% (56/232), and FSH = 16.1% (37/230); P = 0.08]. Pregnancy loss was also similar among treatments [control = 23.1% (15/65), eCG = 18.8% (13/69), and FSH = 14.0% (6/43); P = 0.08]. In addition, the treatments (control, eCG, and FSH, respectively) were not different among ØOF (13.78 ± 0.52; 14.50 ± 0.59; and 15.35 ± 0.69 mm; P = 0.15); TOV (82.50 ± 2.14; 78.48 ± 2.35; and 78.96 ± 2.39 h after P4 withdrawal; P = 0.30); or OR [82.76% (24/29); 83.33% (25/30); and 83.33% (25/30); P = 0.44]. Thus, these data do not indicate a major fertility-enhancing effect of a single eCG or FSH treatment during protocol for TAI in high-producing dairy cows, contrary to the hypothesis of the present study.

Tecnopec, Fazenda Campestre, Agrindus S/A, Echoa e Nutricell Nutrientes Celulares.