Reproductive and molecular responses to a short term treatment for estrus synchronization combined with conventional superovulation in weaned sows

Abstract

Objectives The main objective of this thesis was to assess the efficacy of a short-term estrous synchronization treatment combined with a superovulation (SO) treatment in weaned sows utilized as donors in ET programs. With this purpose, the specific objectives contained in this thesis were to investigate the impact of these combined hormonal treatments on (1) estrus and ovulation response, ovarian characteristics, reproductive outcomes, and the quality and quantity of pre-implantation embryos at day 6 of the cycle, (2) reproductive parameters and gene expression changes in ovaries and endometrium at day 6 of the cycle, (3) gene expression changes in surviving day 6 blastocysts. Methods The general methodology, common to all published articles, includes hormonal treatments, heat detection, artificial insemination (AI), and surgical intervention and obtaining embryos on day 6 of gestation. Five groups of animals were differentiated according to the hormones administered, including a control group without hormonal treatment of any type, another control group with SO treatment and three groups with a combined treatment of SO together with altrenogest (4, 7 and 14 days respectively). for the synchronization of heat. The specific methodology of article 1 includes the evaluation of the embryonic quality of the different groups of sows through morphological assessment, counting the cells of the internal cell mass and trophectoderm, cell apoptosis and cryotolerance. The specific methodology of article 2 includes obtaining endometrium samples from the mesometrial portion of the left uterine horn and left ovary, extraction of total RNA and sequencing to identify differentially expressed genes. The specific methodology of article 3 includes the extraction of total RNA from the embryos and processing of the microarrays to detect differences in gene expression. Conclusions The main conclusions of this doctoral thesis are: 1. The combination of ALT synchronization treatment with SO treatment was effective in delaying post-weaning estrus and in inducing superovulation in weaned multiparous sows. 2. The combination of ALT synchronization treatment with SO treatment negatively affected the interval to the onset of estrus, ovarian status, pregnancy rate, most of the reproductive parameters assessed, and the overall embryo production efficiency. 3. The hormonal treatments (synchronization combined with SO) have the potential to alter ovarian and endometrial gene expression patterns, triggering improper follicle development, and oocyte growth. 4. The hormonal treatments led to the dysregulation in reproductive tissues of genes involved in two critical metabolic pathways for embryo development, the Wnt/β-catenin and Notch signaling pathways. 5. The impact of the synchronization-SO treatments on the number of altered pathways and on the number and FC of DEGs in the surviving day-6 blastocysts was moderate compared to control blastocysts collected from weaned sows with natural estrus. 6. The adverse effects observed in fertilization, embryo production, and the gene expression profiles of the ovaries and uterus resulting from the combined application of synchronization and SO treatments discourage its utilization in ET programs.