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

Abstract

RESUMO -Avaliou-se, durante um ano, o desempenho reprodutivo de 94 vacas leiteiras mestiças Bos taurus × Bos indicus submetidas a um programa de reprodução assistida. Um protocolo de inseminação artificial em tempo fixo (IATF) foi executado por meio de dispositivo intravaginal contendo progesterona e das injeções de prostaglandina F2α e de cipionato de estradiol. Por meio de ultrassonografia, entre 7 e 14 dias após as inseminações ou montas controladas, realizou-se a detecção de corpo lúteo nos ovários a fim de determinar a taxa de ovulação e, no 28 o dia, fez-se o diagnóstico de gestação para cálculo da taxa de concepção. Respeitou-se um período mínimo de 34 dias após o parto antes do tratamento. Não houve influência do escore de condição corporal e da presença de corpo lúteo no início do protocolo, nem da reutilização do dispositivo intravaginal e da monta controlada ou inseminação artificial, sobre as taxas de ovulação, concepção e concepção das vacas ovuladas. As taxas de concepção e de concepção das vacas ovuladas foram afetadas negativamente pelo elevado número de dias pós-parto (DPP), ou dias em lactação e pela época quente do ano, primavera/verão. A resposta ao protocolo de inseminação artificial em tempo fixo baseado no uso de progesterona, PGF2α e cipionato de estradiol é prejudicada pelo aumento dos dias em lactação e pela época quente do ano. A condição corporal não afeta a resposta ao protocolo de inseminação artificial, desde que as vacas tratadas apresentem escore acima de 2,25 pontos.Palavras-chave: concepção, eficiência reprodutiva, ovulação, protocolo de sincronização Timed artificial insemination and early pregnancy diagnosis in crossbred dairy cowsABSTRACT -It was evaluated, during a period of one year, the reproductive performance of 94 Bos taurus × Bos indicus crossbred dairy cows submitted to an assisted reproduction program. A timed artificial insemination (TAI) protocol was carried out by using an intra-vaginal progesterone device containing progesterone and through injections with Prostaglandin F2α and estradiol cypionate. By using ultrasound, from 7 to 14 days after inseminations or controlled mattings, detection of corpus luteum in the ovaries was done to determine ovulation rate and, on the 28 th day, diagnosis of pregnancy was carried out for calculation of conception rate. Treatment only started after a 34-day post-partum minimal period. Body condition score, presence of corpus luteum in the beginning of the protocol, reutilization of intra-vaginal device and controlled mating or artificial insemination did not influence rates of ovulation, conception and conception of ovulated cows. Rates of conception and rates of conception of ovulated cows were negatively affected by the higher number of days post partum (DPP), or days in milk and by the warmer seasons of the year, spring/summer. Response to protocol of timed artificial insemination based on the use of progesterone, PGF2α and estradiol cypionate is negatively affected by lactation days and by the warm season of the year. Bod...

Conception rate and estrous return detection after TAI in Holstein cows

“…In an experiment conducted in Japan with dairy cows submitted to TAI, Yamada (2005) evaluated conception according to DIM between 40 and 221 or more; in this study he also did not identify DIM as an effect on conception rate. Results from the present study were different from the values obtained by Barbosa et al (2011) in a trial also performed in Uberlândia City using crossbred dairy cows. Researchers reported an effect of DIM on conception rate; cows between 34 and 90 DIM had a conception rate of 43.90% and cows with more than 90 days had a conception rate of 23.94%.…”

“…Results obtained in the current study were in accordance with those reported by Barbosa et al (2011), Martel (2008, Souza et al (2009) and Yamada (2005), which also found no interference of CL presence at the onset of a TAI protocol on conception rate of dairy cows. However, Santos et al (2009) showed that ovarian cyclicity at 65 DIM affects conception rate in Holstein cows.…”

“…Barbosa et al (2011) reported a seasonal effect on crossbred dairy cows that showed a conception rate of 42.55% in autumnwinter and 25% in spring-summer. Additionally, Pires et al (2002) found a significant difference on the conception rate of confined Holstein cows after conventional AI in summer and winter, which was confirmed by high variation in THI values occurring in different seasons in the region where the trial was conducted (75.8 in summer vs. 65.3 in winter).…”

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

“…Many studies, also conducted in the Triângulo Mineiro region, discovered that seasonality influenced CR of crossbred dairy cows. According to the results obtained by Barbosa et al (2011), the CR was higher during autumnwinter when compared to spring-summer (42,5% vs. 25.0%). Ayres et al (2014) also reported that CR of crossbred dairy cows submitted to TAI was greater during winter than summer (43.7% vs. 26.9%).…”

Influence of the reuse of progesterone implants in a fixed-time artificial insemination protocol on the conception rates of lactating cows during two different seasons

“…This finding may be due to heat stress observed during the season with the high temperatures, reducing the concentrations of plasma progesterone necessary for recognizing and maintaining a pregnancy. According to Barbosa et al (2011), the conception rate during the fall/winter (42.55%) is higher than the conception rate during the spring/summer (25%) when using implants containing 1.9 g of progesterone in an FTAI protocol. However, this difference was not observed when they compared the reuse of implants.…”