S.D.: writing—original draft preparation, software; C.F.: formal analysis; R.Z.: data curation; Q.J.: writing—review and editing; Y.S., K.Y., S.Z. and J.H.: investigation; R.F.: conceptualization, methodology, project administration, funding acquisition. All authors have read and agreed to the published version of the manuscript. This study was financially supported by the Hunan Engineering Research Center of Intelligent Animal Husbandry (grant number, 20211231GCZX) of China and Evaluation of the Effectiveness of Iron Polysaccharide Supplementation in Pig Diets (grant number, 2021kjc-js060) of Hunan Agricultural University.