Over the last decade, the rapid emergence of multidrug-resistant pathogens has become a global concern, which has prompted the search for alternative antibacterial agents for use in food animals. Antimicrobial peptides (AMPs), produced by bacteria, insects, amphibians and mammals, as well as by chemical synthesis, are possible candidates for the design of new antimicrobial agents because of their natural antimicrobial properties and a low propensity for development of resistance by microorganisms. This manuscript reviews the current knowledge of the basic biology of AMPs and their applications in non-ruminant nutrition. Antimicrobial peptides not only have broad-spectrum activity against bacteria, fungi, and viruses but also have the ability to bypass the common resistance mechanisms that are placing standard antibiotics in jeopardy. In addition, AMPs have beneficial effects on growth performance, nutrient digestibility, intestinal morphology and gut microbiota in pigs and broilers. Therefore, AMPs have good potential as suitable alternatives to conventional antibiotics used in swine and poultry industries.

Exploring strategies to prevent miscarriage in women or early pregnancy loss in mammals is of great importance. Manipulating maternal lipid metabolism to maintain sufficient progesterone level is an effective way. To investigated the embryo loss and progesterone synthesis impacts of short and medium chain fatty acids on the lipid metabolism, pregnancy outcome and embryo implantation were investigated in rats fed the pregnancy diets supplemented without or with 0.1% sodium butyrate (SB), 0.1% sodium hexanoate (SH), or 0.1% sodium caprylate (SC) during the entire pregnancy and early pregnancy, respectively, followed with evaluation of potential mechanisms. Maternal SB, SH, or SC supply significantly improved live litter size and embryo implantation in rats. Serum progesterone, arachidonic acid, and phospholipid metabolites levels were significantly increased in response to maternal SB, SH, and SC supply. The expression of key genes involved in ovarian steroidogenesis and granulosa cell luteinization were elevated in ovaries and primary cultured granulosa cells, including cluster of differentiation 36 (CD36), steroidogenic acute regulatory protein (StAR), and cholesterol side-chain cleavage enzyme (CYP11A1). Additionally, the expression of lysophosphatidic acid receptor 3 (LPA3) and cyclooxygenase-2 (COX2) related with phospholipid metabolism were enhanced in uterus in vivo and in in vitro cultured uterine tissue. In conclusion, maternal SB, SH and SC supply reduced early pregnancy loss through modulating maternal phospholipid metabolism and ovarian progesterone synthesis in rats. Our results have important implications that short or medium chain fatty acids have the potential to prevent miscarriage in women or early pregnancy loss in mammals.

Methicillin-resistant Staphylococcus aureus (MRSA) is the major pathogen responsible for community and hospital bacterial infections. Sublancin, a glocosylated antimicrobial peptide isolated from Bacillus subtilis 168, possesses anti-bacterial infective effects. In this study, we investigated the role and anti-infection mechanism of sublancin in a mouse model of MRSA-induced sublethal infection. Sublancin could modulate innate immunity by inducing the production of IL-1β, IL-6, TNF-α and nitric oxide, enhancing phagocytosis and MRSA-killing activity in both RAW264.7 cells and peritoneal macrophages. The enhanced macrophage function by the peptide in vitro correlated with stronger protective activity in vivo in the MRSA-invasive sublethal infection model. Macrophages activation by sublancin was found to be mediated through the TLR4 and the NF-κB and MAPK signaling pathways. Moreover, oral administration of sublancin increased the frequencies of CD4 ⁺ and CD8 ⁺ T cells in mesenteric lymph nodes. The protective activity of sublancin was associated with in vivo augmenting phagocytotic activity of peritoneal macrophages and partly improving T cell-mediated immunity. Macrophages thus represent a potentially pivotal and novel target for future development of innate defense regulator therapeutics againt S. aureus infection.