Reproduction and reproductive tract morphology of male and female pigs whose mothers were heat stressed during the second month of gestation

Abstract

The primary objective was to assess the development of fetal gonads and measure subsequent reproductive capacity of boars and gilts whose mother was either subjected to gestational heat stress (GHS) or thermoneutral (GTN; control) conditions during pregnancy. Gilts were subjected to either GHS (28 to 38 °C; 65 to 88% relative humidity; n = 30) or GTN (17 to 22 °C; 56 to 65% relative humidity; n = 29) for the second month of gestation (a period that coincides with a critical window of gonadal development). A subset of GHS (n = 12) and GTN (n = 11) gilts were sacrificed immediately following treatment for the collection of pregnancy data. The remaining gilts (n = 18 GHS and n = 18 GTN) were allowed to farrow. Female offspring from the farrowed gilts were studied through puberty, first insemination, and early pregnancy when fetal tissues were again collected. During the treatment period, GHS gilts had greater (P < 0.001) rectal temperature and respiration rate at both measurement timepoints (morning and afternoon) compared with GTN gilts. When assessed at the end of the second month of gestation, the total number of viable fetuses did not differ (P > 0.10) for GHS vs. GTN. Likewise, the weight of the fetus, placenta, fetal testes, and fetal ovaries were similar (P > 0.10) for GHS and GTN pregnancies. There was a tendency for an effect of treatment (63.3 ± 2.3 vs. 70.1 ± 2.6; GHS vs. GTN; P < 0.073) on the number of oogonia per histological section in the fetal ovaries. There was no effect of treatment on the number of prespermatogonia per histological section in the fetal testis. For gilts farrowing after treatment, litter size, piglet birth weight, and weaning weight were similar (P > 0.10) for the GHS and GTN gilts. Testes collected from castrated GHS boars had fewer prespermatogonia per seminiferous tubule cross section (P < 0.049). Female offspring from the GHS (n = 30) or GTN (n = 37) sows reached puberty at a similar age and their pregnancies (ninth week of gestation) had fewer corpora lutea (15.6 ± 0.5 vs. 17.1 ± 0.4; GHS vs. GTN; P < 0.038) but the number of fetuses was similar for GHS and GTN. In summary, compared with GTN, GHS during a critical window of gonadal development tended to reduce the number of oogonia in the fetal ovary, reduced the number of prespermatogonia in the neonatal testes, and reduced ovulation rate at first pregnancy in gilts.

Managing prolific sows in tropical environments

“…High ambient temperature and humidity during the hot period of the year can have detrimental effects on the reproductive performance of gilts or sows and also affect reproductive tract morphology of their offspring (Bernhard et al, 2020). Pregnant gilts subjected to heat stress (28-38°C) during the second month of gestation produced foetuses that had a lower number of oogonia per histological section in their ovaries (Bernhard et al, 2020). Moreover, testes collected from piglets whose mothers had been exposed to heat stress also had fewer prespermatogonia per seminiferous tubule cross section (Bernhard et al, 2020).…”

“…Pregnant gilts subjected to heat stress (28-38°C) during the second month of gestation produced foetuses that had a lower number of oogonia per histological section in their ovaries (Bernhard et al, 2020). Moreover, testes collected from piglets whose mothers had been exposed to heat stress also had fewer prespermatogonia per seminiferous tubule cross section (Bernhard et al, 2020). Additionally, gilts from sows exposed to heat stress had fewer corpora lutea during pregnancy compared to those from mothers exposed to thermoneutral conditions during pregnancy (Bernhard et al, 2020).…”

“…Moreover, testes collected from piglets whose mothers had been exposed to heat stress also had fewer prespermatogonia per seminiferous tubule cross section (Bernhard et al, 2020). Additionally, gilts from sows exposed to heat stress had fewer corpora lutea during pregnancy compared to those from mothers exposed to thermoneutral conditions during pregnancy (Bernhard et al, 2020). These findings indicated that the environmental temperature and humidity during gestation in gilts and sows should be controlled to improve the future reproductive performances of their offspring and enhance overall reproductive potential of hyperprolific sows in tropical countries.…”