Control of follicular development and ovulation for artifical insemination, superovulation and fixed-time transfer of embryos

Abstract

The difficulty to detect estrus in zebu (Bos taurus indicus) and buffalos (Bubalus bubalis) has limited the use of artificial insemination in these species. One way to solve this problem is to develop hormonal treatments capable of synchronizing ovulation and allow fixed time artificial insemination, i.e, artificial insemination without need for estrus detection. The purpose of the present project is to explore several aspects related to the pharmacological control of the estrous cycle, from physiological and pharmacological background to field trials of hormonal treatments capable of improving or facilitating artificial insemination and embryo transfer in bovine and buffalos. Additionally, the training of students (undergraduate and graduate) will be emphasized and the knowledge originated by the project will be disseminated to students, veterinarians, farmers and producers through a congress that will deal specifically with pharmacological control of the estrous cycle, and conferences that will take place in several states of our country. The following topics and experiments will be developed in the present project: 1) synchronization of ovulation and timed artificial insemination (TAl), in beef cattle: a) low cost protocols and treatments potentially useful for animals in anestrus. Low cost protocols (GPE e EPE) will be tested in 5 experiments (total of 20 experimental groups) and treatments with progesterone/progestagen associated with estrogens, eCG or GnRH will be tested in 3 experiments (total of 12 experimental groups); b) fat supplementation in Nelore cows associated with TAl. In this experiment (total of 2 experimental groups) it will be tested if fat supplementation increases the reproductive performance of cows timed AI; 2) synchronization of evulation and TAl, in dairy cattle: a) effect of treatments to synchronize ovulation on pregnancy rate of crossbred cows (Bos indicus x Hollstein). Modifications on GPE protocol and association of this protocol with progesterone will be tested in 2 experiments (total of 8 experimental groups); b) effect of follicles removal, during maternal recognition of pregnancy, on pregnancy rate of dairy cows timed AI. It will be tested in 2 experiments (total of 6 experimental groups) if removal of follicles at the time of maternal recognition of pregnancy increases the pregnancy rate of dairy cows Tal...(AU)