The iron status of sows has a great influence on reproductive performance. Iron deficiency reduces reproductive performance and newborn piglet survival rate of sow. The hemoglobin is a potential predictor for the iron status of sows and is convenient for rapid detection in pig farms. However, the relationship between iron status, hemoglobin, placental trace elements, and reproductive performance remains unclear. In this study, the hemoglobin and reproductive performance of more than 500 sows with first to sixth parities at different gestation stages (25, 55, 75, 95, and 110 d of gestation) in two large-scale sow farms were collected, and the content of placental Fe, Zn, Mn, and Cu was analyzed. The results show that hemoglobin levels of sows during pregnancy (days 75, 95, and 110) decreased significantly (P < 0.001). As the parity increases, the hemoglobin levels of sows at days 25 and 55 of gestation and placental mineral element contents including Fe, Zn, Mn, and Cu at delivery decreased (P < 0.05), while the litter size, birth alive, and litter weights increased gradually (P < 0.001). Furthermore, hemoglobin during pregnancy had a negative linear correlation with litter weight and average weight (P < 0.05), and higher hemoglobin at day 25 of gestation may reduce the number of stillbirths (P = 0.05), but higher hemoglobin at day 110 of gestation may tend to be a benefit for the birth (P = 0.01). And there was a significant positive linear correlation between hemoglobin at day 110 of gestation and placental Fe and Mn levels (P = 0.002, P = 0.013). There was also a significant positive linear correlation among Fe, Zn, Mn, and Cu in the placenta (P < 0.001). The levels of Fe, Zn, and Mn in the placental at delivery were positively related to the average weight of the fetus (P = 0.048, P = 0.027, P = 0.047), and placental Cu was linearly correlated with litter size (P = 0.029). Our research revealed that the requirements for iron during gestation were varied in different gestation periods and parities. The feeds should be adjusted according to the gestation periods, parities, or iron status to meet the iron requirements of sows and fetal pigs.
Keywords: gestation; hemoglobin; iron status; pregnant sows; reproductive performance.
Iron deficiency and iron excess may cause adverse outcomes during pregnancy. In sows’ feed, iron is added as ferrous sulfate, ferrous glycine, or other forms to improve their reproductive performance and prevent iron-deficiency anemia in their offspring. However, it is always ineffective and iron-deficiency anemia often occurs in piglets. To explore the iron requirements in pregnant sows, we conducted a large-scale farm study to track the hemoglobin levels, placental trace element content, and reproductive performances of hundreds of sows. The correlation between the hemoglobin levels, placental trace element content, and reproductive performance indicators of sows during pregnancy at different parities was analyzed. We found that pregnancy hemoglobin level of sows decreases during the gestation and varies at different parities. The hemoglobin level of sows during pregnancy was linearly negatively correlated with reproductive performance. The content of iron, zinc, manganese, and copper in the placenta was linearly positively correlated. Our results revealed that iron deficiency or excess in sows’ feed may not be conducive to the improvement of reproductive performance, and the optimal iron supplementation dose during pregnancy may depend on the iron status and number of fetuses of sow.
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