Effects in air-exposed corn silage of medium chain fatty acids on select spoilage microbes, zoonotic pathogens, and in vitro rumen fermentation

Authors: ARZOLA-ALVAREZ, CLAUDIO - Universidad Autonoma De Chihuahua; RUIZ-BARRERA, OSCAR - Universidad Autonoma De Chihuahua; CASTILLO-CASTILLO, YAMICELA - Universidad Autonoma De Chihuahua; ONTIVEROS, MARINA - Universidad Autonoma De Chihuahua; FONSECA, MOZART - University Of Nevada; JONES, BARBARA - Tarleton State University; SMITH, WILLIAM - Tarleton State University; Hume, Michael; Harvey, Roger; Poole, Toni; Anderson, Robin; ARZOLA-LIRA, ALEJANDRO - Universidad Autonoma De Chihuahua; SALINAS-CHAVIRA, JAIME - University Of Tamaulipas

Submitted to: Journal of Environmental Science and Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2023
Publication Date: 1/20/2023
Citation: Arzola-Alvarez, C., Ruiz-Barrera, O., Castillo-Castillo, Y., Ontiveros, M., Fonseca, M., Jones, B.W., Smith, W.B., Hume, M.E., Harvey, R.B., Poole, T.L., Anderson, R.C., Arzola-Lira, A., Salinas-Chavira, J. 2023. Effects in air-exposed corn silage of medium chain fatty acids on select spoilage microbes, zoonotic pathogens, and in vitro rumen fermentation. Journal of Environmental Science and Health. 58:45-50. https://doi.org/10.1080/03601234.2023.2168449.
DOI: https://doi.org/10.1080/03601234.2023.2168449

Interpretive Summary: Fermented animal feeds, called silages, have long been used to preserve the nutritional quality of feeds during storage. Exposure of the fermented feed to air, during the feeding period, can allow for the growth of spoilage and pathogenic microbes which can ruin the nutritional quality of the feed and risk infection of the animal and the foods they produce. In this study, we tested the antimicrobial effects of natural medium chain fatty acids commonly found in foods, such as coconut and palm kernel oil, when spayed onto air-exposed silage and observed that a mixture of two oils, commonly named caprylic and capric acid, caused a 1000-fold decrease in the numbers of yeast and molds. Additionally, we observed that this oil mixture, as well as several other oil treatments, decreased numbers of a group of bacteria known to be carriers of antimicrobial resistant traits but had minimal effect on beneficial lactic acid bacteria. In a follow up experiment to test the effects of the oil-treated silage on gut digestion, we observed little, if any, negative effects of treatment on digestibility of the silage. This research provides useful information that will help livestock producers better preserve and use their fermented feedstuffs, thereby helping them produce wholesome and microbiologically-safe meat and milk for the American consumer.

Technical Abstract: The effects of medium chain fatty acid (MCFA) treatment of aerobically-exposed silage on spoilage and pathogenic microbes and rumen fermentation were evaluated in vitro. In experiment one, four g (wet basis) of overnight air-exposed silage were suspended in 10 mL of water and treated with 0.03 g of C6, C8, C10, or mixtures containing equal proportions of C6:C8:C10:C12 or C8:C10 fatty acids. After 24 h of aerobic incubation at 37oC, microbial enumeration of samples collected at 0 and 24 h revealed 3 log10 CFU/g decreases (P < 0.05) in wild-type populations of yeast and molds cultured from C8:C10-treated silage when compared to controls. Compared to controls, populations of wild-type enterococci were decreased (P < 0.05) by all treatments except in the C6 to C12 mixture; lactic acid bacteria were decreased (P < 0.05) by all treatments except by C6 and by the C6 to C12 mixture. Conversely, wild-type populations of total aerobes and experimentally-inoculated populations of a multi-drug resistant/methicillin-resistant Staphylococcus aureus and Listeria monocytogenes were unaffected by treatment (P > 0.05). In experiment two, anaerobic incubation (24 h at 39oC) of freshly collected ruminal fluid (10 mL) with 0.02 g of overnight air-exposed MCFA-treated corn silage (dry matter basis) revealed higher hydrogen accumulations (P < 0.05) only in the C8:C10 mixture when compared to controls. Accumulations of methane, acetate, propionate, butyrate, or estimates of hexose fermented were unaffected by treatment. Acetate: propionate ratios were higher (P < 0.05) and estimates of fermentation efficiency were lower (P < 0.05) in silages treated with C8 or the C8:C10 mixture than controls. Results reveal little negative effect of MCFA treatment on ruminal fermentability of silage and antimicrobial effects against some spoilage microbes. Further research is warranted to optimize treatment formulations to specifically target undesired microbes without adversely affecting beneficial microbes.