Effect of reproductive methods and GnRH administration on long-term protocol in Santa Ines ewes |
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Authors: | Biehl Marcos V Ferraz Junior Marcos V C Ferreira Evandro M Polizel Daniel M Miszura Alexandre A Barroso José P R Oliveira Gabriela B Bertoloni Analisa V Pires Alexandre V |
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Institution: | 1.Department of Animal Science, Luiz de Queiroz College of Agriculture, University of S?o Paulo, Pádua Dias Avenue, n. 11, PO Box 09, Piracicaba, S?o Paulo, 13418-900, Brazil ;2.Department of Nutrition and Animal Production, College of Veterinary and Animal Science, University of S?o Paulo, Duque de Caxias North Avenue, n. 225, Pirassununga, S?o Paulo, 13635-000, Brazil ;3.Department of Animal Science, State University of Ponta Grossa, General Carlos Cavalcanti Avenue, n. 4748, Ponta Grossa, Paraná, 84030-900, Brazil ; |
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Abstract: | This study aimed to determine whether reproductive performance of ewes submitted to laparoscopic timed artificial insemination (TAI) would be similar to ante meridiem (AM)/post meridiem (PM) rule and assisted natural mating (NM), and whether GnRH may enhance the pregnancy rate in TAI. In experiment I, 191 non-lactating ewes were synchronized, then TAI was performed either 48 h after progesterone (P4) removal (TAI-48 h) or 12 h after estrus detection (AM/PM); moreover, some ewes were submitted to NM (NM) as control treatment. In experiment II, 247 non-lactating ewes were allocated in five treatments, a control (no-GnRH on protocol) and four treatments arranged in a factorial design 2 × 2. The factors were time and dose of GnRH: ewes that received either 10 μg (TAI-10 μg-36 h) or 25 μg of GnRH (TAI-25 μg-36 h) 36 h after P4 removal and ewes that received either 10 μg (TAI-10 μg-48 h) or 25 μg of GnRH (TAI-25 μg-48 h) at time of insemination, 48 h after P4 removal. In experiment I, pregnancy rate in TAI-48 h was lower (P = 0.03) than AM/PM and NM. Moreover, the probability of pregnancy in TAI-48 h was higher (P = 0.06) in ewes detected in estrus early. In experiment II, the use of GnRH in TAI protocols increased (P < 0.01) pregnancy rate at synchronization, and TAI-25 μ-48 h and TAI-10 μg-36 h treatments increased (P = 0.02) pregnancy rate compered to TAI-10 μg-48 h. We conclude that TAI decreased pregnancy rate compered to NM and AM/PM, which may be improved by GnRH use in TAI to synchronize ovulation. |
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