Location: Food and Feed Safety ResearchTitle: Ruminal bacterial, archaeal, and fungal diversity of dairy cows in response to ingestion of lauric or myristic acid Author
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2012
Publication Date: 9/5/2012
Publication URL: http://handle.nal.usda.gov/10113/57238
Citation: Hristov, A.N., Callaway, T.R., Lee, C., Dowd, S.E. 2012. Ruminal bacterial, archaeal, and fungal diversity of dairy cows in response to ingestion of lauric or myristic acid. Journal of Animal Science. 90:4449-4457. Interpretive Summary: Normal functioning of the digestive system of cattle depends on the actions of a mixed microbial consortium of bacteria, archaea, fungi, and protozoa. When protozoa were eliminated by chemical means, methanogenic archaea populations changed, as did some bacterial populations. Prevotella and Bacteroides populations were reduced while Eubacterium and Butyrivibrio populations were increased. Fungal populations were largely unchanged. Collectively, results indicate that defaunation significantly altered bacterial and archaeal populations in the rumen of dairy cows, but the effects on fungal populations remains unclear.
Technical Abstract: The objective of this experiment, part of a larger study, was to investigate changes in rumen bacterial, archaeal, and fungal diversity in cows with normal and reduced protozoal populations. In the main study, 6 lactating dairy cows were dosed intraruminally with 240 g/cow per day of stearic (control), lauric (LA), or myristic (MA) acids in a replicated 3 × 3 Latin square design trial. Experimental periods were 28 d, and cows were refaunated between periods. Lauric acid reduced protozoal counts in the rumen by 96%, compared with SA and MA (MA had no effect on ruminal protozoa). Whole ruminal contents samples were collected at 2, 4, 6, 8, 10, 14, 18, and 24 h following the morning feeding on d 23 of each experimental period, stored frozen, and later composited by cow and period for microbial profile analyses. In the present study, we utilized a new molecular method, tag-encoded FLX amplicon pyrosequencing (TEFAP), that can perform diversity analyses of gastrointestinal bacterial, archaeal, and fungal populations of cattle. The LA treatment, through its effect on protozoa, directly had a profound effect on the microbial ecology of the rumen. Ruminal populations of Prevotella, Enterorhabdus, and Bacteroides were reduced (P < 0.05) by more than 2-fold in LA treatments compared with SA, and Clostridum and Ruminococcus populations were reduced (P < 0.05 and P = 0.06, respectively) in LA compared with MA-treated cows. Eubacterium, Olsenella, TM7, and Butyrivibrio genera populations were increased (P < 0.05) by LA compared with MA or SA. The LA treatment, likely through its effect on ruminal protozoa, resulted in an increase (P < 0.05) in the Archaeal methanogenic genera Methanobacteria and a decrease (P < 0.05) in Methanobrevibacter. Few changes in fungal populations caused by treatment were detected. Collectively, the present results indicate that LA, likely through its antiprotozoal effect, significantly altered bacterial and archaeal populations in the rumen of dairy cows, but the effects on fungal populations remains unclear.