Oral propylene glycol modifies follicular fluid and gene expression profiles in cumulus-oocyte complexes and embryos in feed-restricted heifers

Nutritional Strategies to Promote Bovine Oocyte Quality for In Vitro Embryo Production: Do They Really Work?

The ability of bovine oocytes to reach the blastocyst stage (i.e., embryo with around 150 cells in cattle) in vitro can be affected by technical (e.g., culture medium used) and physiological factors in oocyte donors (e.g., age, breed). As such, the nutritional status of oocyte donors plays a significant role in the efficiency of in vitro embryo production (IVEP), and several nutritional strategies have been investigated in cattle subjected to ovum pick-up (OPU). However, there is no clear consensus on the reliability of nutritional schemes to improve IVEP in cattle. Available evidence suggests that a moderate body condition score (i.e., 3 in a 1-5 scale) in cattle is compatible with a metabolic microenvironment in ovarian follicles that will promote embryo formation in vitro. The usefulness of fatty acid and micronutrient supplementation to improve IVEP in cattle is debatable with the current information available. Overall, the supply of maintenance nutritional requirements according to developmental and productive stage seems to be enough to provide bovine oocyte donors with a good chance of producing embryos in vitro. Future nutrition research in cattle using OPU-IVEP models needs to consider animal well-being aspects (i.e., stress caused by handling and sampling), which could affect the results.

Unraveling propylene glycol-induced lipolysis of the biosynthesis pathway in ultra-high temperature milk using high resolution mass spectrometry untargeted lipidomics and proteomics

In July 2022, the food safety accident that excessive propylene glycol was detected in milk processing factory raised widespread concerns about quality and nutrition of milk with illegal additive. To the best of our knowledge, the influences of propylene glycol to lipids in milk had not been systematically explored. Therefore, spatiotemporal distributions of lipids related to propylene glycol reaction and changes of sensory quality were investigated by food exogenous. Briefly, 10 subclasses (Cer, DG, HexCer, LPC, LPE, PC, PE, PI, SPH and TG) included 147 lipids and 38 pivotal enzymes were annotated. Propylene glycol altered lysophospholipidase and phospholipase A₂ through altering structural order in lipids domains surrounding proteins to inhibit glycerophospholipid metabolism and initiated obvious changes in PC (10.45-27.91 mg kg^-1) and PE (12.92-49.02 mg kg^-1). This study offered insights into influences of propylene glycol doses and storage time on milk metabolism at molecular level to assess the quality of milk.

Impact of oocyte donor age and breed on in vitro embryo production in cattle, and relationship of dairy and beef embryo recipients on pregnancy and the subsequent performance of offspring: A review

Genomic selection combined with in vitro embryo production (IVEP) with oocytes from heifer calves provides a powerful technology platform to reduce generation interval and significantly increase the rate of genetic gain in cattle. The ability to obtain oocytes with developmental competence from calves has been recognised for more than 60years. There is renewed interest in the potential of this reproductive technology as the beef and dairy industries seek to identify and multiply animals that satisfy consumer demand for efficient utilisation of natural resources, with minimal environmental impact and high product quality. Heifer calves show a good follicular response to FSH stimulation and oocytes can be recovered by ovum pick-up (OPU). However, the efficiency of OPU/IVEP remains lower for calves compared with peripubertal heifers and cows, in both indicus (Zebu, Bos indicus ) and taurus (Bos taurus ) breeds. Indicus cattle generally have more follicles, yield a greater number of oocytes, and have a better IVEP outcome, compared with taurus cattle. The treatment of prepubertal heifers with bovine somatotrophin (bST) and propylene glycol before OPU/IVEP has yet to show a major improvement in embryo production. Holstein (taurus) dairy heifers derived from different reproductive technologies (AI, MOET, OPU/IVEP) showed a similar age at puberty and first-lactation milk production. OPU/IVEP Holstein embryos transferred to beef or dairy cows likewise yielded heifers with the same performance. The gains in productivity that can be achieved with strategic use of OPU/IVEP in heifer calves make this a relevant and highly important reproductive technology in cattle breeding. Ongoing optimisation of the technology is needed for the potential of OPU/IVEP in young donors to be fully realised.

Use of pregnancy-associated plasma protein-A during oocyte in vitro maturation increases IGF-1 and affects the transcriptional profile of cumulus cells and embryos from Nelore cows

Insulin-like growth factor 1 (IGF-1) activity is established by the regulation of IGF binding protein activity, which blocks IGF-1 functions, whereas pregnancy-associated plasma protein-A (PAPP-A) improves IGF-1 bioavailability and facilitates binding to IGF receptors. To further extend our understanding of the effect of exogenous PAPP-A on bovine embryo production, we added this protein during in vitro maturation of cumulus-oocyte complexes (COCs); moreover, we assessed its effects on IGF-1 quantity in the maturation medium, embryonic yield and postwarming survival, blastocyst quality, and transcript abundance. Bovine COCs were matured in a serum-free medium, either with PAPP-A supplementation (100 ng/ml) or without (control). The treatment group produced higher IGF-1 concentrations in the maturation medium; however, showed no difference on cleavage, blastocysts rates, and embryonic survival 3 and 24 hr postcryopreservation. Regarding gene expression, VNN1 was upregulated, whereas AGPAT9, FASN, EGFR, HAS2, and IMPDH1 were downregulated in PAPP-A treated. PAPP-A treated, CPT2, DNMT3A, and TFAM were upregulated, whereas ATF4 and IFITM3 were downregulated. We concluded that although the addition of PAPP-A did not affect embryo yield and blastocyst survival, higher IGF-1 levels may affect embryo competence through differential expression of genes involved in lipid metabolism, oocyte competence, and mitochondrial function.

From clinics to (cow)mics: a reproductive journey

This manuscript describes the different topics I have been involved in the fields of reproductive physiology and embryo biotechnologies with attempts to address practical issues raised mainly by the breeding industry. The journey started with phenotyping work in the field of reproductive physio-pathology. Other issues were related to the optimization of reproductive biotechnologies to favorize genetic selection. The implementation of genomic selection raised opportunities to develop the use embryo biotechnologies and showed the interest of combining them in the case of embryo genotyping. There is still a need to refine phenotyping for reproductive traits especially for the identification of markers of uterine dysfunction. It is believed that new knowledge generated by combining different molecular approaches will be the source of applications that may benefit AI practice and embryo technologies.