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Title:   Author  item
                                            Vallet, Jeffitem
                                            KLEMCKE, HAROLD - FORMER ARS EMPLOYEEitem
                                            Christenson, Ronalditem
                                            PEARSON, PAUL - FORMER ARS EMPLOYEE
  Submitted to: Journal of Animal Science
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 6/6/2003
                                    Publication  Date: 9/1/2003
                                    Citation: VALLET, J.L., KLEMCKE, H.G., CHRISTENSON, R.K., PEARSON, P.L. THE EFFECT OF BREED AND INTRAUTERINE CROWDING ON FETAL ERYTHROPOIESIS ON DAY 35 OF GESTATION IN SWINE. JOURNAL OF ANIMAL SCIENCE. 2003. 81(9). p. 2352-2356.Interpretive Summary: Our previous work suggested that the development of red blood cells by the fetus during pregnancy in pigs was (1) impaired when crowding within the uterus resulted in the generation of fetuses of less than normal weight, (2) more rapid in Meishan gilts, which are suspected of having greater fetal survival under crowded uterine conditions. Results also suggested that many fetuses were dying in the crowded uterine environment between days 30 and 40, suggesting that this is a very important period of pregnancy with regard to the effect of crowding on fetal survival. Because of the experimental design, our previous data were not sufficiently extensive before day 40 of pregnancy, nor were we able to examine the period between day 30 and 40. Thus, we designed an experiment to compare red blood cell development between white crossbred gilts and Meishan gilts and between a normal uterine environment and a crowded uterine environment on day 35 of pregnancy. Results confirmed that fetal blood hemoglobin decreased with decreasing fetal weight. They also confirmed more rapid red blood cell development in the Meishan. These results are consistent with the hypothesis that impairment of fetal red blood cell development in a crowded uterine environment could contribute to the poor survival of small fetuses, thus affecting litter size of swine. They also confirmed that more rapid blood cell maturation in Meishans could be one mechanism whereby this breed accomplishes greater litter size.
                                Technical Abstract: A previous study suggested that intrauterine crowding impaired fetal erythropoiesis and that fetal erythropoiesis was accelerated in Meishan pigs during early pregnancy. Because these conclusions were based on limited numbers of observations, a second experiment was undertaken to provide a more extensive investigation of these phenomena. Intact White crossbred gilts, unilaterally hysterectomized-ovariectomized (UHO) White crossbred gilts and intact Meishan gilts (n = 13 to 16/group) were mated after at least one estrous cycle of normal length (17 to 23 d). Gilts were laparotomized at d 35 of pregnancy, the remaining uterine horn was exteriorized and opened near each fetus, and a blood sample was collected from each fetus. The uterine horn was then surgically removed, and each fetus and placenta was weighed. All fetal blood samples were measured for hematocrit, red blood cell number, and hemoglobin.  The percent nucleated cells, percent reticulocytes and erythropoietin were also measured in blood samples from the largest and smallest living fetus in each litter. Fetal hematocrits were not affected by treatment. Blood cell counts were greater (P < 0.01) in fetuses of Meishan gilts than in White Crossbred intact or UHO gilts. Hemoglobin was less (P < 0.01) in fetuses of Meishan gilts than in fetuses of White crossbred intact or UHO gilts. The percent nucleated (immature) blood cells and percent reticulocytes were both  less (P < 0.01) in fetuses of Meishan-intact gilts. Erythropoietin was also lower (P < 0.01) in fetuses of Meishan gilts. As observed previously, fetal weight was correlated with blood hemoglobin. These data confirm that fetal erythropoiesis in Meishan gilts is accelerated compared to WC gilts. These results suggest that faster blood cell development could be beneficial to fetal survival in swine.


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