Fertility in Gyr Cows (Bos indicus) with Fixed Time Artificial Insemination and Visual Estrus Detection Using a Classification Table

Abstract

The aim of this research was to compare two artificial insemination protocols (AIP): hormonal synchronization with fixed time artificial insemination (SC-FTAI) and the use of a table based on visual observation of estrus signs (VO) in order to identify cows in natural or spontaneous estrus being assigned to AI (NSE-IA). Two groups were formed: in the first group 109 cows were assigned to SC-FTAI, in which a commercial protocol is used; the second one included 108 randomly chosen cows, which were assigned to NSE-AI and in this group a modified table was used. Response variable was first service fertility rate (FSF), which was coded 1 for pregnant and 0 for empty. Predictor variables were AIP, postpartum anestrus, daily milk yield, body condition score at AI and calving number. Statistical analyses included association chi-square tests and logistic regression. Results showed an overall 41.94% FSF and a significant association was detected (P < 0.05) between FSF and daily milk yield; pregnancy rates were 42.20% and 41.67% for the SC-FTAI and NSE-IA groups, respectively (P > 0.05). The odds ratio for the effect of AIP was only 1.050, suggesting no differences in FSF between groups. The NSE-AI protocol can enhance both the technique of VO and reproductive efficiency. Further validation of the table is required.

Comparison of Two Insemination Programs in Synchronized Early Postpartum Zebu Cows under Tropical Conditions: An Economic Appraisal

“…A certain bias was present in our fertility calculations following AI as 70% of animals conceiving is quite a high figure when compared to values reported in the literature [24] [25]. A more realistic figure would be around 30% to 40%.…”

Tasa de concepción en vacas lecheras inseminadas a celo detectado o a tiempo fijo

“…El incremento de la eficiencia reproductiva lograda a través del protocolo de IA a tiempo fijo pudo ser debido a que se logró optimizar el desarrollo folicular y se tuvo una mayor certeza de que la ovulación ocurrió de forma simultánea a la IA (Carvalho et al, 2015). Algunos estudios (Ramírez-Iglesia et al, 2014;Rodríguez-Martínez et al, 2018) indican similitudes en la tasa de concepción cuando las vacas son inseminadas a tiempo fijo o a celo detectado. Estos estudios indican que la falta de respuesta al protocolo Ovsynch está relacionada con los días postparto en los cuales es aplicado, observándose menores tasas de gestación cuando las vacas son sincronizadas entre el día 60 y 75 (26%) en comparación cuando se sincronizan después del día 76 (43%); en este experimento las vacas tenían 80 días en lactancia por lo que se puede considerar como un momento ideal para la aplicación del protocolo utilizado.…”

Weaning weight and optimization of reproductive efficiency in Nellore females subjected to timed artificial insemination

“…According to Ferraz et al (2012), about 80% of the herds in Brazil consist of the zebu species (Bos taurus indicus), which are mostly managed under extensive grazing systems, a fact that makes it difficult to detect estrus. Additionally, estrus in Zebu cows has shown to be of low intensity and short duration, making its detection even more difficult (Ramírez-Iglesia et al, 2014).…”