Effect of oestrous resynchronization on the reproductive efficiency of zebu cows

Abstract

The aim of this study was to develop a resynchronization strategy before the return of oestrus in cows diagnosed as not pregnant after fixed‐time artificial insemination (TAI). A total of 839 cows, approximately 45 days post‐partum, were synchronized using TAI. On day 0, intravaginal progesterone‐releasing devices were inserted and 2 mg of oestradiol benzoate was administered. Eight days later (D8), the progesterone‐releasing devices were removed and oestradiol cypionate (0.5 mg, eCG [300 IU]) and prostaglandin (7.5 mg) were administered. All cows were inseminated between 48 and 56 hr after device removal (D10). Thirty days after TAI, cows that were not diagnosed as pregnant by ultrasound were immediately resynchronized and again inseminated at a fixed time. The hormonal protocol used in the first and second rounds of TAI was the same. The pregnancy rate after the first TAI was 52%, and after the second TAI, it was 49%. The increase in the total pregnancy rate (synchronization + second oestrous synchronization) compared to a single synchronization was 23.5%. In conclusion, resynchronization of oestrus and ovulation in zebu cows that had previously undergone TAI protocols is effective in increasing the reproductive efficiency.

Inseminación artificial a tiempo fijo y reinseminación de vacas para carne tratadas con y sin gonadotropina coriónica equina

“…El porcentaje de gestación en la primera IATF resultó superior a valores reportados en otros estudios que reportan gestaciones de 52 % (Faleiro et al, 2019), 50 % (Pereira et al, 2018) y 38.6 % (Torres-Júnior et al, 2014. Otros autores coinciden con nuestros resultados en que hay una disminución en la tasa de gestación después de la segunda IATF en relación con la gestación en la primera (de Oliveira et al, 2015).…”

“…Otros autores coinciden con nuestros resultados en que hay una disminución en la tasa de gestación después de la segunda IATF en relación con la gestación en la primera (de Oliveira et al, 2015). Las diferencias en los estudios señalados podrían atribuirse a varios factores como las diferentes fuentes de progesterona utilizadas en el protocolo de sincronización, manejo nutricional, CC de las vacas y control de enfermedades reproductivas (Faleiro et al, 2019).…”

“…De manera similar a lo observado en el presente estudio, de Oliveira et al (2015) y deOliveira et al (2019) subrayaron que la tasa de concepción promedio acumulada fue del 80.5 % y 81.6 %, respectivamente; sin embargo, ellos reportan un porcentaje promedio de gestación de 54 % y 56 % en la primera IATF, ligeramente inferior al observado en este estudio. En otros experimentos(Sá Filho et al, 2014;Faleiro et al, 2019) lograron tasas de gestación acumuladas del 75 %, ligeramente inferiores a los datos descritos en el presente estudio. Del mismo modo, Campos et al de gestación, las vacas diagnosticadas como preñadas gestantes se excluyen de las inyecciones hormonales que se aplican al retirar el DIV, mientras que las vacas no gestantes continúan con el Inseminación artificial a tiempo fijo y reinseminación de vacas para carne tratadas con y sin gonadotropina coriónica equina Nº 27, Vol.…”

Strategic re-use of intravaginal progesterone devices increases conception rate in primiparous Nellore cows

“…According to Vasconcelos et al (2017), several strategies can be used to increase overall pregnancy rates in FTAI protocols, especially in regions with potential for improvement. For instance, in the Amazon region, the application of FTAI using protocols based on progesterone and estrogens has shown satisfactory results in multiparous beef cows (Faleiro et al, 2019).…”

Follicular Dynamics and Pregnancy Rate in Nellore Heifers Submitted to Fixed-Time Artificial Insemination Protocols (FTAI)

“…The reproductive efficiency of cattle herds is influenced by several factors, such as the breeding system, the breed used, the management employed on the farm, and the sanitary and nutritional status of the animals [ 1 , 2 ]. Despite this variety of factors that interfere in animal reproduction, the use of reproductive biotechnologies in the bovine herd has shown positive results, and it is of fundamental importance for the economic growth of national cattle breeding [ 3 , 4 , 5 , 6 ].…”