13 USE OF A NEW INTRAVAGINAL DEVICE TO RELEASE PROGESTERONE IN FIXED-TIMED ARTIFICIAL INSEMINATION IN NELLORE COWS (BOS TAURUS INDICUS)

Abstract

Artificial insemination results can be improved using fixed-timed AI (FTAI). Currently, progesterone release devices, indispensable in FTAI procedures, such as DIB^® (Schering-Plough, Kenilworth, NJ, USA), are made of silicone, a nonbiodegradable biocompatible polymer. Recently, biodegradable progesterone (P4)-releasing devices made of poly(3-hydroxy)butyrate-valerate copolymer (PHB-V) and poly-ϵ-caprolactona (PCL) have been developed. To investigate the efficiency on pregnancy rate of FTAI programs using a new intravaginal device made of PHB-V (Progestar^®, Innovare, São Paulo, Brazil), 240 Nellore (Bos indicus) cows, between 3 and 8 years of age, were randomly assigned to 2 experiments. In experiment 1, new P4 devices DIB (control group, DIB1; n = 60) were compared with PHB-V (Progestar1; n = 76); in experiment 2, previously used DIB (DIB2; n = 52) and PHB-V (Progestar2; n = 52) devices were compared. All groups were treated with 2 mg of estradiol benzoate i.m. (Innovare) and received the intravaginal device according to group (Day 0). Together with P4 device withdrawal (Day 8) all animals received 300IU of eCG i.m. (Novormon^®, Schering-Plough) and 150 μg i.m. of D-cloprostenol (Croniben^®, Biogenesis-Bagó, Buenos Aires, Argentina). On Day 9, all cows were treated with 1 mg of estradiol benzoate and the FTAI was performed 30 h later. The data were submitted to ANOVA (PROC GLM of SAS, SAS Institute, Cary, NC, USA), separating as causes of variance the effect of treatment, postpartum period (PPP1-45 until 70 days and PPP2-71 until 90 days), body condition score (BCS4, BCS5, and BCS6 using a 1 to 9 scale), cyclicity (cycling and noncycling) and clean-up bulls (5 bulls nominated with numbers 1 to 5). Significant differences were considered to have P < 0.05. In experiment 1, interactions were not significant, there was no effect of treatment on FTAI (DIB1: 66.7% v. Progestar1: 65.8%) or breeding season pregnancy rates (BSPR; DIB1: 95.0% v. Progestar1: 94.7%) and no effect of other variables on FTAI pregnancy rates (FTAIPR) and BSPR. In experiment 2 there was no effect of treatment on FTAIPR (DIB2: 61.6% v. Progestar2: 55.8%) and BSPR (DIB2: 94.2% v. Progestar2: 88.5%). As ANOVA indicated a significant effect of clean-up bulls on BSPR, Tukey test was used to split it up. A bull of the Progestar2 group had lower performance (41.7%) causing the difference (albeit nonsignificant) on BSPR. This experiment showed that Progestar and DIB had the same efficiency on pregnancy rate and both treatments have the potential to produce FTAIPR >50% and BSPR >90%.

Fapesp-Fundação de Amparo à Pesquisa do Estado de São Paulo. CNPq-Conselho Nacional de Desenvolvimento Científico e Tecnológico.