Impact of litter size on the hematological and iron status of gilts, sows and newborn piglets: a comparative study of domestic pigs and wild boars

Abstract

Background The critically low hepatic iron stores of newborn piglets are considered to be a major cause of neonatal iron deficiency in modern breeds of domestic pig (Sus domestica). The main factor believed to contribute to this phenomenon is large litter size, which has been an objective of selective breeding of pigs for decades. As consequence, iron transferred from the pregnant sow has to be distributed among a greater number of fetuses. Results Here, we investigated whether litter size influences red blood cell (RBC) indices and iron parameters in Polish Large White (PLW) piglets and gilts. Small and large litters were produced by the transfer of different numbers of embryos, derived from the same superovulated donor females, to recipient gilts. Piglets from large litters obtained following routine artificial insemination were also examined. Our results clearly demonstrated that varying the number of piglets in a litter did not affect the RBC and iron status of 1-day-old piglets, with all showing iron deficiency anemia. In contrast, gilts with small litters displayed higher RBC and iron parameters compared to mothers with large litters. A comparative analysis of the RBC status of wild boars (having less than half as many piglets per litter as domestic pigs) and PLW pigs, demonstrated higher RBC count, hemoglobin level and hematocrit value of both wild boar sows and piglets, even compared to small-litter PLW animals. Conclusions These findings provide evidence that RBC and iron status in newborn PLW piglets are not primarily determined by litter size, and indicate the need to study the efficiency of iron transport across the placenta in domestic pig and wild boar females.

Iron Supplementation of Pregnant Sows to Prevent Iron Deficiency Anemia in Piglets: A Procedure of Questionable Effectiveness

“…Knowledge about iron transport across the placenta is crucial for planning iron supplementation in pregnant sows. In 2016, after Cao and Fleming [17] recalled the importance of the placenta in iron metabolism, much research has been devoted to transplacental iron transport and its regulation [18,19]. The placenta is a highly vascularized organ responsible for the exchange of nutrients and gases between the mother and developing fetus.…”

“…In this process, Iron is delivered to the placenta by the maternal circulation, where it is mainly bound to transferrin (Tf), forming a monomeric or diferric (holo) Tf-Fe 3+ complex. The primary route of iron uptake by the placenta involves the uptake of Tf-bound iron from the maternal circulation through transferrin receptor 1 (TfR1) on the apical membrane of the placental syncytiotrophoblast facing the maternal circulation [17,27]. The Tf-Fe 3+ complex binds to TfR1 and then is internalized into the cell by clathrin-mediated endocytosis.…”