Abstract
The objective of this study was to evaluate placental development during late gestation (day 100) between Chinese Meishan (CM; n = 7) and White crossbred (WC; n = 5) gilts following intrauterine crowding induced by unilaterally hysterectomy-ovariectomy. Gross placental morphology and areolae density as well as histological morphology (i.e., folded bilayer and placental stroma) were analyzed using computer-assisted morphometry for placentas of the smallest and largest fetuses within each litter. There was a breed by fetal size interaction (P < 0.01) for areolae density in which placentas for large CM fetuses had greater areolae density compared to small CM fetuses, but the density of areolae was greater for CM fetuses compared to WC fetuses, irrespective of fetal size. The width of the folded bilayer was greater (P < 0.01) in placentas for WC gilts compared to CM gilts, irrespective of fetal size. Placentas for small fetuses had greater (P < 0.01) folded bilayer width compared to large fetuses, irrespective of breed. The placental stromal width was greater (P < 0.01) in placentas for large fetuses compared to small, irrespective of breed. The difference between stromal width in placentas between divergent-sized littermates, however, was greater (P = 0.05) in WC gilts compared to CM gilts, indicating there was a limited response to intrauterine crowding in CM gilts. These results indicate there is an altered placental development during late gestation in CM compared to WC gilts, thus, there are likely different mechanisms for responding to intrauterine crowding between breeds.
Highlights
The slopes of the linear regressions correspond to the allometric growth rate within each litter and tended to be less (P = 0.0712) in Chinese Meishan (CM) compared to White crossbred (WC) gilts (Table 1)
There was a tendency (P = 0.0591) for a breed by fetal size interaction in placental width (Table 2) because placentas for CM littermates were similar in width but placentas for WC gilts differed in size and the largest placentas for littermate WC gilts were wider than all other placentas
Considering the importance of the placental areolae for the uptake of glandular secretion, the greater density and development of the areolae in CM compared to WC gilts when there was intrauterine crowding in the present study indicates this is a mechanism by which CM gilts have a lesser effect of intrauterine crowding on fetal and placental growth
Summary
Increased piglet mortality has been due, in part, to greater within-litter birth weight variation and the production of smaller littermate piglets due to limitation in uterine capacity and fetal crowding (Roehe and Kalm, 2000; Mesa et al, 2006). The development of the placenta has direct implications on uterine capacity, fetal growth and survival as well as postnatal piglet growth and survival (Vallet et al, 2002, 2014). Histotrophic exchange occurs during later stages of gestation when there is exchange of many different glycoproteins (Friess et al, 1981; Bazer et al, 2012), uteroferrin, which contributes to transfer of iron from the maternal to the fetal tissues (Roberts et al, 1986) with this being indicative of the importance of the placental areolae as gestation progresses. Adequate hemotrophic and histotrophic exchange across the placenta is essential for growth and development of the fetus and the well-being of neonatal piglets
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
