Strategies to improve the in vitro embryo production (IVEP) of Holstein (Bos taurus), Gyr (Bos indicus) and Nellore (Bos indicus) young donors

Abstract

The use of young animals for reproduction is of great interest for the beef and dairy production chains, especially regarding the use of in vitro embryo production (IVEP), because it contributes to the maximization of the herd's potential, allowing the reduction of generation intervals and increase of genetic gain due to rapid dissemination of high value genetic material. Among the factors that may compromise the results of this technology, the donor's age has great importance. Many studies have verified that prepubertal heifers present reduced IVEP efficiency (Presicce et al., 1997; Guerreiro, 2015; Baruselli et al., 2016; Warzych et al., 2017; Bayeux, 2015), which compromises the use of this animal category for IVEP. Therefore, it is of ought most importance to perform studies that search for techniques that may validate and improve the efficiency of IVEP in this animal category. Thus, the objective of Experiment 1 is: 1) evaluate the IVEP of Holstein (Bos taurus) calves (3-8 months) treated with FSH, rBST and the association of FSH + rBST and; 2) compare blood levels of AMH, glucose, insulin and IGF-1 of the animals from each experimental group. The objective of Experiment 2 is: 1) evaluate the IVEP of Gyr (Bos indicus) calves (3-8 months), pubertal heifers (12-22 months) and cows treated or not with FSH and; 2) compare blood levels of AMH, glucose, insulin and IGF-1 of the animals from each experimental group. The objective of Experiment 3 is: 1) evaluate the IVEP of 12 and 24 months old Nellore (Bos indicus) heifers treated or not with FSH and; 2) compare blood levels of AMH, glucose, insulin and IGF-1 of the animals from each experimental group. The hypothesis are 1) Holstein calves treated with FSH and/or rBST have greater follicular diameter at OPU, increase of blood level IGF1 and greater oocyte competence, which improves IVEP when compared to animals that do not receive treatment; 2) Gyr females treated with FSH have greater follicular diameter at OPU and oocyte competence, resulting on improved IVEP when compared to animals that do not receive treatment and; 3) Nellore heifers treated with FSH have greater follicular diameter at OPU and oocyte competence, resulting on improved IVEP when compared to animals that do not receive treatment. (AU)