Effects of lower doses of cloprostenol intramuscular or into vulvar submucosa on estrus induction and pregnancy rates in Nelore cows

Abstract

The present study aims to compare the effects of lower doses of cloprostenol intramuscular (IM) or into vulvar submucosa (IVS) on estrus induction and pregnancy rate in Nelore cows. A total of 100 cycling Nelore cows with body condition score (BCS 3.5) 1 to 5 scale (Radostitis; Blood, 1986) and 170±11 days postpartum. Females were randomly divided in 5 groups (N=20) G1 to G5 and treated with cloprostenol (CiosinÒ) on day 0 (D0) and on day 11 (D11) if not detected in estrus. Cows were injected with 500mg IM (G1), 250mg IM (G2), 125mg IM (G3), 250mg IVS (G4) and 125mg IVS (G5). Estrus was observed twice a day and the females artificially inseminated 12 hours after heat detection. There was no statistical difference (P > 0.80) between groups in the estrus induction (first injection to estrus interval): 16/20 - 96.00 hours (G1), 13/20 - 90.42 hours (G2), 10/20 - 84.45 hours (G3), 15/20 – 87.86 hours (G4), 12/20 - 81.25 hours (G5) and second injection (P > 0.10): 4/20 – 67.50 hours (G1), 7/20 – 85.50 hours (G2), 10/20 - 57.00 hours (G3), 5/20 – 70.60 hours (G4), 8/20 – 60.00 hours (G5). There was no statistical difference (0.65^ns) between groups in the pregnancy rates: 40% (G1), 45% (G2), 50% (G3), 40% (G4), 40% (G5). The results demonstrate that the treatments with lower doses of cloprostenol intramuscular or into vulvar submucosa may be used to induce heat with similar pregnancy rates in cycling Nelore cows with good body condition.