A Short-Term Altrenogest Treatment Post-weaning Followed by Superovulation Reduces Pregnancy Rates and Embryo Production Efficiency in Multiparous Sows

Abstract

Although embryo transfer (ET) is a biotechnology ready for the swine industry, there are factors to be solved, the availability of embryo donors as one. Multiparous sows as donors ought to be considered since weaning is a natural and efficient method for estrus synchronization. In addition, superovulation treatments at weaning are effective in increasing the efficiency of donor embryo production. However, ET programs typically require more donors than those available from a single weaning, imposing grouping several weanings to establish a batch for ET. Since short-term administration of Altrenogest is effective in delaying estrus after weaning without effects on ovulation and embryo development, we investigated how Altrenogest combined with superovulation would affect reproductive parameters and embryo quality and quantity of weaned multiparous donor sows. The sows were administered Altrenogest from the day of weaning for 14 (SS-14 group; N = 26), 7 (SS-7 group; N = 31) and 4 (SS-4 group; N = 32) days. The sows were superovulated with eCG 24 h after the last administration of Altrenogest and with hCG at the onset of estrus. Sows not treated with Altrenogest that were superovulated with eCG 24 h post-weaning and hCG at the onset of estrus (SC group; N = 37) and sows with natural estrus after weaning (C group; N = 34) were used as control groups. The percentage of sows showing estrus within 10 days was not affected by the treatment, but the interval from Altrenogest withdrawal to estrus was longer (P < 0.05) in the SS groups than the interval from weaning to estrus in the controls. SS treatments increased (P < 0.05) the percentage of sows with ovarian cysts and the development of polycystic ovaries. The pregnancy and the fertilization rates, and the overall embryo production efficiency were also negatively affected by the SS treatments (P < 0.05). Interestingly, almost 70% of the structures classified as unfertilized oocytes or degenerated embryos in sows from the SS groups were immature oocytes. In conclusion, although superovulation of weaned sows was highly efficient, short-term administration of Altrenogest in combination with superovulation had negative effects on most of the reproductive parameters assessed, particularly affecting the overall efficiency of pregnancy and embryo production.

GnRH agonists: Updating fixed‐time artificial insemination protocols in sows

“…Recent studies described that altrenogest administration in combination with gonadotropins had negative impacts on fertility and embryo viability for multiparous sows (Gonzalez-Ramiro et al, 2021.…”

“…Altrenogest also acts at genetic level by downregulation of CYP17A1 mRNA in the prepubertal theca layer and PGF2 alpha synthase expression in the granulosa and theca layer of mature gilts. Recent studies described that altrenogest administration in combination with gonadotropins had negative impacts on fertility and embryo viability for multiparous sows (Gonzalez‐Ramiro et al, 2021, 2022).…”

The Use of a Brief Synchronization Treatment after Weaning, Combined with Superovulation, Has Moderate Effects on the Gene Expression of Surviving Pig Blastocysts

“…However, the situation becomes very different when superovulation is induced after the St-ALT treatment. Recently, we have shown that St-ALT administration before superovulation was efficient in delaying postweaning estrus and increasing the ovulation rates in weaned sows, but the treatments decreased fertilization, pregnancy, and embryo production rates compared to ALT-untreated, superovulated sows [13,14]. The poor results achieved after the combined use of St-ALT and superovulation treatments were mainly due to the increased proportions of immature oocytes and degenerated embryos compared to those obtained in ALT-untreated, superovulated sows and sows with natural estrus after weaning.…”

“…It has recently been shown that the combination of these treatments alters the gene expression patterns in the ovary and endometrium, mainly dysregulating key metabolic pathways, which could lead to inadequate follicle and oocyte growth and preimplantation embryo developmental ability [14]. Although the quality of the surviving blastocysts after St-ALT plus superovulation treatment, in terms of total trophectoderm and inner cell mass cells, apoptosis rates, and cryotolerance [13], was similar to that observed in ALT-untreated, superovulated sows and in natural postweaning estrus sows, the treatment can influence not only oocyte maturation and fertilization but also surviving embryos at the molecular level. The aim of the present investigation was to establish the extent to which St-ALT treatment in combination with a standard superovulation protocol in weaned sows caused variations in the overall transcriptome of day 6 embryos.…”

Immunological uterine response to pig embryos before and during implantation

“…A better knowledge of the immunological mechanism underlying the establishment and maintenance of pregnancy in pigs is essential for the design of strategies to improve their reproductive efficiency. This challenge is especially relevant in the context of porcine ET; a technology that can notably contribute to improve sanitary, productive and, ultimately, economic aspects of the pig commercial sector (Gonzalez‐Ramiro et al., 2021 ). In addition, other relevant biotechnologies, such as gene editing or cloning, are highly dependent on ET (Martinez, Martinez, et al., 2019 ).…”