Effect of intra-uterine growth restriction on long-term fertility in boars

The present study assessed the effect of birthweight on reproductive performance, including a possible mechanism, in male pigs. Ten newborn male piglets, including five normal birthweight (NBW) piglets and five intra-uterine growth restricted (IUGR) piglets, were used in the study. All piglets were weaned on Day 28 and fed the same diet during the experiment (10 months). Average daily weight gain, feed intake and the feed conversion ratio were higher in NBW than IUGR piglets. Similarly, testis volume and the number of Leydig and Sertoli cells in the distal portion of the testes were higher in NBW than IUGR piglets (P<0.05). Semen volume (P<0.05) and the total number of spermatozoa per ejaculate (P=0.08) were lower in IUGR boars. Testosterone concentrations on Day 141 and prostaglandin E₂ concentrations on Days 82 and 141 were higher in IUGR than NBW boars (P<0.05). The malondialdehyde content of seminal plasma was higher in IUGR boars, whereas sperm glutathione peroxidase activity was lower in IUGR versus NBW boars (P<0.05). Expression of DNA methyltransferase (Dnmt) genes Dnmt1, Dnmt3a, histone-lysine N-methyltransferase (Suv39h2), and lysine (K)-specific demethylase Kdm4a was upregulated in testes from IUGR boars. These findings suggest that growth restriction affects sperm production via reproductive organ development and epigenetic regulation.