Effects of service number on conception rate in Japanese Black cattle

Abstract

The conception rate (CR) of Japanese Black cattle has been decreasing since 1990. The objectives of this study were to compare CR by artificial insemination (AI) number, and to assess the interaction between AI number and possible factors related to CR in Japanese Black cattle. Records of 11,182 AI records for 6,741 heifers and 61,302 AI records for 13,139 cows on 977 farms were analysed. The average CR of heifers was 47.0%, and CR at the first, second and third AI was higher than at the fourth or subsequent AI (p < 0.05). The average CR of cows was 47.8%, and their CR at first and second AI was higher than the fourth or subsequent AI (p < 0.05). Data analysis with CR as the dependent variable revealed significant interactions of AI number with interval from calving to first AI and AI season. Cows first serviced at ≤48 days post-partum had lower CR than those at ≥90 days at first AI (p < 0.05), but the interval from calving to first AI did not affect CR at second AI. Cows serviced in the autumn had a higher CR at first AI than those serviced in the spring and winter (p < 0.05); however, there was no seasonal difference in CR at the second AI. In summary, CR began to decrease from the fourth AI in heifers and the third AI in cows. The AI season and the interval from calving to first AI significantly affected CR only at the first AI.

Effect of oestrous resynchronization on the reproductive efficiency of zebu cows

“…Resynchronization facilitates greater use of TAI, which is favourable to allow for cross‐breeding, replacement of genetically superior matrices, greater standardization of batches of calves and reduction in the amount of bulls needed. Our results along with the study by Irikura et al, (, ) suggest that future studies on resynchronization, followed by a third AI treatment under tropical conditions, could also aid in maximizing the reproductive efficiency.…”

“…Previous research (Irikura, Uematsu, Kitahara, Osawa, & Sasaki, , ) showed an increase in pregnancy rate after a third artificial insemination (AI). Resynchronization facilitates greater use of TAI, which is favourable to allow for cross‐breeding, replacement of genetically superior matrices, greater standardization of batches of calves and reduction in the amount of bulls needed.…”

Association of interservice interval with conception rate in Japanese Black cattle

“…The data we analysed were a subset of a larger data set from a previous study that contained 86,348 artificial insemination (AI) records of 50,482 parity records in 16,746 animals on 1,006 farms raising Japanese Black cattle in Miyazaki between July 2005 and April 2010 (Irikura et al., ). In this study, heifers and cows that failed to be conceived at least once were extracted from the data set to investigate the association of ISI with CR.…”

“…Low conception rate (CR) and a failure to detect a cow returning to oestrus after service could extend the interservice interval (ISI) and decrease the efficiency of calf production resulting in economic loss. The CR at first service in Japanese Black cattle, the most common beef cattle breed in Japan also known as “Wagyu,” is approximately 46.5% (Irikura, Uematsu, Kitahara, Osawa, & Sasaki, ), that is about half of cows inseminated need to be reinseminated. Detection of failed inseminations and timely reinsemination of cows is a challenge that can shorten the ISI and improve reproductive efficiency.…”

Introduction of a plasmid and a protein into bovine and swine cells by water-in-oil droplet electroporation

“…In Japan, livestock animals are bred mainly through artificial insemination. A decrease in the rate of conception is one of the doi: 10.1292/jvms.19-0475 greatest challenges especially for dairy farmers [10,18]. The low conception rate may be attributed to the fertilizing capacity of sperm [28].…”