Milking cessation (dry period) and the period around parturition from 8 weeks prepartum to 1 week postpartum represent critical phases of mammary tissue remodeling and physiological transition in dairy ruminants. This presentation summarizes two studies that examine how bacterial infection disrupts milk antimicrobials and udder involution during the dry period, and the dynamics of innate antimicrobial in goats across the peripartum transition. To simulate bacterial infection, lipopolysaccharide (LPS) was infused at milking cessation. Results showed that, in healthy dry udders, water reabsorption made the milk yellow and thick, concentrating somatic cells and functional proteins derived from mammary epithelial cells (MECs). These proteins include the iron-binding lactoferrin (LF) which inhibits bacterial growth, the direct bactericidal cathelicidin-7 (Cath-7) which disrupts pathogen cell membranes, and the calcium-binding antimicrobial S100A8. Conversely, the LPS group showed reduced in SCC and the secretion of LF, Cath-7, and S100A8, while leukocyte-derived Cath-2 exhibited only a transient increase. Furthermore, LPS group resulted in a significantly larger lobule area and a smaller connective tissue area, proving that inflammation directly halts mammary involution. In the peripartum model, Cath-7 and S100A8 increased toward kidding to serve as a defense shield. Following parturition, these components declined sharply due to colostrum dilution and blood-milk barrier closure. In conclusion, udder immunity relies on MECs both to execute tissue involution and to build a defense shield; early inflammation disrupts both processes. Therefore, animals suffering from mastitis must fully recover before entering the dry period.
- Sun, J., N. Suzuki, T. Nii, and N. Isobe. 2024. Effect of different inflammation states on the antimicrobial components in milk of goat udders after milking cessation. Anim. Sci. J., 95(1), e13926.
- Sun, J-k., Z-L. Liang, T. Nii, N. Suzuki, and N. Isobe. 2025. Antimicrobial component concentrations in the milk of peripartum goats. Anim. Sci. J., 96(1), e70029.
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