Factors Affecting Conception Rates Following Artificial Insemination or Embryo Transfer in Lactating Holstein Cows

Abstract

The objective of this study was to evaluate the factors that may affect conception rates (CR) following artificial insemination (AI) or embryo transfer (ET) in lactating Holstein cows. Estrous cycling cows producing 33.1 +/- 7.2 kg of milk/d received PGF2alpha injections and were assigned randomly to 1 of 2 groups (AI or ET). Cows detected in estrus (n = 387) between 48 and 96 h after the PGF2alpha injection received AI (n = 227) 12 h after detection of estrus or ET (n = 160) 6 to 8 d later (1 fresh embryo, grade 1 or 2, produced from nonlactating cows). Pregnancy was diagnosed at 28 and 42 d after estrus, and embryonic loss occurred when a cow was pregnant on d 28 but not pregnant on d 42. Ovulation, conception, and embryonic loss were analyzed by a logistic model to evaluate the effects of covariates [days in milk (DIM), milk yield, body temperature (BT) at d 7 and 14 post-AI, and serum concentration of progesterone (P4) at d 7 and 14 post-AI] on the probability of success. The first analysis included all cows that were detected in estrus. The CR of AI and ET were different on d 28 (AI, 32.6% vs. ET, 49.4%) and 42 (AI, 29.1% vs. ET, 38.8%) and were negatively influenced by high BT (d 7) and DIM. The second analysis included only cows with a corpus luteum on d 7. Ovulation rate was 84.8% and was only negatively affected by DIM. Conception rates of AI and ET were different on d 28 (AI, 37.9% vs. ET, 59.4%) and 42 (AI, 33.8% vs. ET, 46.6%) and were negatively influenced by high BT (d 7). The third analysis included only ovulating cows that were 7 d postestrus. Conception rates of AI and ET were different on d 28 (AI, 37.5% vs. ET, 63.2%) and 42 (AI, 31.7% vs. ET, 51.7%) and were negatively influenced by high BT (d 7). There was a positive effect of serum concentration of P4 and a negative effect of milk production on the probability of conception for the AI group but not for the ET group. The fourth analysis was embryonic loss (AI, 10.8% vs. ET, 21.5%). The transfer of fresh embryos is an important tool to increase the probability of conception of lactating Holstein cows because it can bypass the negative effects of milk production and low P4 on the early embryo. The superiority of ET vs. AI is more evident in high-producing cows. High BT measured on d 7 had a negative effect on CR and embryonic retention.

Behavioral and hormonal pattern of repeat breeder cows around estrus

“…No other studies and RB (filled circle) cows; average E 2 concentartion in blood relative to E 2 peak (B) in CTRL (filled square) and RB (filled circle) cows; average LH concentartion in blood relative to LH peak (C) in CTRL (filled square) and RB (filled circle) cows. Demetrio et al 2007, Cummins et al 2012. However, in this study, in spite of slightly longer estrus-toovulation interval in the RB cows than in the CTRL cows (31.5 vs 28.9 h; NS), all the CTRL and RB respondent cows ovulated within the normal range.…”

Inseminação artificial em tempo fixo e diagnóstico precoce de gestação em vacas leiteiras mestiças

“…Não foi detectado efeito de número de dias pós-parto ou de dias em lactação na taxa de ovulação (Tabela 1), diferindo dos resultados encontrados por Demétrio et al (2007), que verificaram que com o aumento do número de dias pós-parto, houve redução da probabilidade de ovulação em vacas Holandesas de alta produção, o que não foi observado neste estudo, provavelmente devido ao uso de vacas mestiças de menor produção. As vacas com dias pós-parto ou dias em lactação menor que 90 tiveram maior taxa de concepção do que as com mais de 90 dias (P<0,05; Tabela 1), diferindo dos resultados de Tenhagen et al (2003), que, ao usarem o protocolo Ovsynch sem DIP4, relataram que vacas inseminadas em tempo fixo, com maior número de dias pós-parto ou dias em lactação, tiveram maior taxa de concepção ao primeiro serviço, quando comparadas a outras de saúde as excluía do estudo.…”

Influence of seasonality, timing of insemination and rectal temperature on conception rate of crossbred dairy cows

“…Vasconcelos et al (2011) evaluated RT associated with seasonality seven days after TAI or during fixed-time bovine embryo transfer (ET) in Holstein dairy cows and reported that the highest average value of RT occurred during summer. Demétrio et al (2007) concluded that a high RT measured seven days after AI or during ET had a negative effect on the conception of Holstein dairy cows. Pires et al (2002) showed higher CR during winter when compared with summer (71.2% vs. 45.7%).…”