Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/28/2000
Publication Date: 1/1/2001
Citation: Vallet, J.L., Christenson, R.K., Klemcke, H.G., Pearson, P.L. 2001. Intravenous infusion of iron and tetrahydrofolate does not influence intrauterine uteroferrin and secreted folate-binding protein content in swine. Journal of Animal Science. 79(1):188-192. Interpretive Summary: Our recent results implicate the efficiency of red blood cell formation as a possible factor influencing the survival of piglets before and after birth. Iron and folate (a B vitamin) are known to be required for efficient red blood cell formation, thus improving the delivery of these nutrients to the developing piglet during pregnancy may increase litter size of swine. Experiments performed in which extra iron and folate was given to pregnant sows did not consistently lead to an increase in litter size. However, circulating blood levels of these nutrients are tightly regulated and uterine transport of these nutrients to the developing piglet undergoes dramatic changes during pregnancy, which also suggests tight regulation. Thus both potentially interfere with the delivery of exogenous iron and folate to the developing piglet. Whether extra iron and folate given to sows actually results in improved delivery to the developing pig has not been investigated. We treated pregnant pigs with iron and folate and measured the secretion of iron and folate transport proteins by the uterus. The amount of these proteins present in the uterus during early pregnancy were unaffected. Thus, a more productive strategy to modifying iron and folate delivery to developing piglets is to understand and manipulate uterine mechanisms governing transport protein secretion rates. This should improve delivery of these vital nutrients to the developing piglet, red blood cell development, survival rates and litter size.
Technical Abstract: Numerous studies with equivocal results have been performed to determine the effect of exogenous iron and folate on reproductive performance in swine. However, the effect of exogenous iron and folate on secretion of their respective uterine transport proteins has never been reported. Twenty gilts were infused (n = 5 per treatment) with either (1) saline, (2) alpha-tocopherol, (3) alpha-tocopherol plus iron citrate or (4) alpha-tocopherol plus tetrahydrofolate on d 11 to 14 of pregnancy. On d 14, blood samples were obtained at 0, 2, 4, 6, 8, and 24 h after infusion and samples were measured for plasma iron and folate. Gilts were slaughtered on d 15 and the reproductive tracts were recovered. Each uterine horn was flushed with 20 mL saline and the average number of somites within conceptuses from each flush was determined. Conceptus tissues were separated from the uterine flushings by centrifugation and the uterine flushings were measured for total protein, total retinol binding protein, total acid phosphatase and total folate binding protein. Intravenous infusion of iron citrate and tetrahydrofolate increased (P < 0.05) plasma iron and folate, respectively, for 6 to 8 h but had no effect on uterine content of uteroferrin or secreted folate binding protein. These data suggest that uterine secretion of uteroferrin and secreted folate binding protein are not influenced by plasma levels of iron and folate, respectively, and may provide an explanation for the equivocal effect of iron and folate treatment on reproductive performance in gilts.