Julia Linck Moroni | ALES Graduate Seminar

A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Julia Linck Moroni. This seminar is open to the general public to attend.

Thesis Topic: The influence of low litter birth weight phenotype on placental and embryonic development at day 30 of gestation in multiparous sows

MSc with Dr. Michael Dyck.

Seminar Abstract:

The low litter birth weight phenotype (LLBWP) in sows represents a concern for the swine industry. The ability to predict this trait could be strategically directed toward selection for higher production efficiency. The aim of this study was to understand the biological processes associated with the litter birth weight phenotype in order to improve overall breeding efficiency, lifetime productivity and number and quality of pigs weaned per sow in the breeding herd.For this research, analyses were conducted on reproductive data from a purebred Large White maternal line (Hendrix Genetics), to identify sows (>2 parities) with repeatable high litter birth weight phenotype (HLBWP) or LLBWP (top 12% and bottom 12% of the population), with 7 to 22 total number born. A total of 40 sows were selected (n=20 HLBWP and n=20 LLBWP) and bred with semen from purebred Large White boars of proven fertility (Hendrix Genetics) on their second estrus following estrus synchronization with altrenogest (Matrix^tm, Merck AH, Kenilworth, NJ). Sows were euthanized on day 28-30 of gestation (mean ± sd; day 29.15 ± 0.6) and samples of placenta, and embryos collected. Total number of embryos (TNE), embryonic weight (EW), embryonic viability, and crown-rump length (CRL) measurements were recorded, along with the ovulation rate (OR) and allantochorionic fluid volume (AFV). The difference between TNE and OR was considered an indicator of early embryonic survivability, while the ratio between TNE and number of viable embryos was an indicator of late embryonic survivability. No significant difference was detected (P > 0.05) in OR (LLBWP: 25.6 ± 1.06; HLBWP: 26.8 ± 1.06), TNE (LLBWP: 19.5 ± 1.19; HLBWP: 19.8 ± 1.12) and number of viable embryos (LLBWP: 16.4 ± 1.37; HLBWP: 16.6 ± 1.37) on day 30 of gestation. Consequently, no differences were found for early embryonic survivability (LLBWP: 0.78 ± 0.02; HLBWP: 0.76 ± 0.02, P=0.43), late embryonic survivability (LLBWP: 0.85 ± 0.01; HLBWP: 0.86 ± 0.01, P = 0.67) or total embryonic survivability (LLBWP: 0.67 ± 0.02; HLBWP: 0.66 ± 0.02, P = 0.55). For embryonic and placental characteristics, there was no significant difference between LLBWP and HLBWP for EW (LLBWP: 0.80 ± 0.05 g; HLBWP: 0.88 ± 0.04 g, P=0.18) or CRL (LLBWP: 21.5 ± 0.7 mm; HLBWP: 21.9 ± 0.68 mm, P=0.46). However, placental development represented by the average AFV was significantly lower in the LLBWP compared to HLBWT group (LLBWP: 131 ± 9.82 mL; HLBWP: 149 ± 9.39 mL, P= 0.03). All viable embryos (n=610) were sex-typed by PCR. There was no significant effect of sex on these measures of embryonic development. Within each litter birth weight phenotype group, 4 sows with the individual EW falling within the mean EW of the group ± SD were selected for embryonic and placental gene expression analyses (Illumina Next Generation Sequencing). Several differential expressed genes (DEGs) involved in biological pathways associated with ion and gas transportation, placental morphogenesis and hemodynamics, cellular metabolic process, detoxification process and regulation of cell proliferation were identified when comparing the transcriptome between the two litter birth weight phenotype groups. Therefore, in our study LLBWP sows showed unfavorable intrauterine environment at day 30 of development, which leads to impaired embryonic development and consequent lower BW of entire litters.