Follicle and corpus luteum size and vascularity as predictors of fertility at the time of artificial insemination and embryo transfer in beef cattle

摘要

: Two ultrasound based fertility prediction methods were tested prior to embryo transfer (ET) and artificial insemination (AI) in cattle. Female bovines were submitted to estrous synchronization prior to ET and AI. Animals were scanned immediately before ET and AI procedure to target follicle and corpus luteum (CL) size and vascularity. In addition, inseminated animals were also scanned eleven days after insemination to target CL size and vascularity. All data was compared with fertility by using gestational diagnosis 35 days after ovulation. Prior to ET, CL vascularity showed a positive correlation with fertility, and no pregnancy occurred in animals with less than 40% of CL vascularity. Prior to AI and also eleven days after AI, no relationship with fertility was seen in all parameters analyzed (follicle and CL size and vascularity), and contrary, cows with CL vascularity greater than 70% exhibit lower fertility. In inseminated animals, follicle size and vascularity was positive related with CL size and vascularity, as shown by the presence of greater CL size and vascularity originated from follicle with also greater size and vascularity. This is the first time that ultrasound based fertility prediction methods were tested prior to ET and AI and showed an application in ET, but not in AI programs. Further studies are needed including hormone profile evaluation to improve conclusion. Index Terms:??Fertility; follicle; corpus luteum; ultrasound; color-Doppler; cattle Resumo: Duas t??cnicas de predi?§?￡o de fertilidade, baseadas em ultrassonografia, foram testadas no momento da transfer?ancia de embri?μes (TE) e insemina?§?￡o artificial (IA) em bovinos. F?ameas bovinas foram submetidas a protocolos de sincroniza?§?￡o de estro para TE e IA. Os animais foram escaneados por ultrassonografia imediatamente antes do procedimento de TE e IA para identificar o tamanho e vasculariza?§?￡o do fol?-culo e corpo l?oteo (CL). Al??m disso, os animais inseminados foram escaneados onze dias ap?3s a insemina?§?￡o para identificar o tamanho e vasculariza?§?￡o do CL. Todos os dados foram comparados com a fertilidade utilizando-se do diagn?3stico gestacional 35 dias ap?3s a ovula?§?￡o. No momento da TE, a vasculariza?§?￡o do CL apresentou-se positivamente relacionada com a fertilidade, sendo que animais com menos de 40% de vasculariza?§?￡o do CL n?￡o ficaram gestantes. No momento da IA, assim como onze dias ap?3s a IA, nenhuma rela?§?￡o foi encontrada entre fertilidade e os par?￠metros analizados (tamanho e vasculariza?§?￡o do fol?-culo e CL), enquanto que contrariamente, houve uma queda na fertilidade em vacas com vasculariza?§?￡o do CL acima de 70%. Nos animais inseminados, o tamanho e vasculariza?§?￡o do fol?-culo foi positivamente relacionado ao tamanho e vasculariza?§?￡o do CL, demonstrado pela presen?§a de um CL maior e mais vascularizado proveniente de um fol?-culo maior e mais vascularizado. O presente estudo ?? o primeiro a mostrar m??todos de predi?§?￡o de fertilidade baseados em ultrassonografia no momento da IA e TE, demonstrando uma aplicabilidade pr??tica no momento da TE. Novos estudos s?￡o necess??rios para suportar os resultados mostrados, incluindo an??lises hormonais. Termos de Indexa?§?￡o:??Fertilidade; fol?-culo; corpo l?oteo; ultrassonografia; Doppler colorido; bovino Introduction Assisted reproduction techniques (ART) are highly diffused in cattle industry, aiming to increase herd fertility as well synchronize births and homogenate the herd age for slaughter. Artificial insemination (AI) and embryo transfer (ET) can be defined as the major ART techniques in cattle industry. These two ART techniques are efficient and with suitable results for cattle production, although a "fine tuning" is necessary to achieve even greater reproductive results. New studies aimed to increase herd fertility index by hormone treatments (Bisinotto et al. 2011) or improving semen quality (Kastelic et al. 2008). However, the evaluation of the success of each new approach used to increase herd fertility is, in practice, only measured by gestational diagnosis 35 days after ovulation. Earlier pregnancy detection is not been used yet, although was already tested (Siqueira et al. 2013), mainly by transrectal ultrasonography. Early gestational diagnosis had aimed to improve herd production, since it could enable an early reintroduction of the non-pregnant cows in reproduction, and an increased number of pregnant animals in a shorter time. In addition, real time methods to predict fertility at the time of AI and ET procedure were also previously tested (Silva et al. 2006, Siddiqui et al. 2008, S?? Filho et al. 2010a). Therefore, an immediate diagnosis to help the decision of using or discarding an animal from an AI or ET program is still questionable. Follicle vascularity and its effects on fertility had been investigated in mares (Silva et al. 2006) and cows (Shrestha et al. 2006, Siddiqui et al. 2008). Near ovulation, was shown that a