Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2017
Publication Date: 5/5/2017
Citation: Welch, K.D., Stonecipher, C.A., Gardner, D.R., Cook, D., Pfister, J.A. 2017. Changes in the rumen bacterial microbiome of cattle exposed to ponderosa pine needles. Journal of Animal Science. 95:2314–2322. doi: 10.2527/jas2016.1228.
Interpretive Summary: Ponderosa pine needles are known to induce abortions in cows when consumed during the last trimester of pregnancy. The toxin in ponderosa pine needles that induces abortions in cattle is the labdane resin acid isocupressic acid (ICA). Pine needles also contain lesser amounts of other related labdane acids including agathic acid (AA), imbricatoloic acid (IMB) and dihydroagathic acid (DHAA), which may also be abortifacient. A previous study demonstrated that cattle conditioned to ponderosa pine needles can more efficiently metabolize the abortifacient compounds than naïve cattle. These results suggest that extended exposure of cattle to pine needles results in a physiological change in cattle such that the known abortifacient compounds in ponderosa pine needles are metabolized more quickly. The physiological adaptation appears to include an alteration in the ability of rumen microflora to metabolize the pine needles. Therefore, the objective of this study was to perform an analysis of the microbiome in the rumen of cattle before, during and after exposure to pine needles in order to identify rumen microbial changes that occur during pine needle exposure. This results from this study demonstrated that exposure of cattle to pine needles caused a clear shift in the rumen microbiome composition. This shift lasted less than 1 week post exposure, which indicates that any prophylactic treatment to manipulate the ruminal metabolism of the abortifacient compounds in pine needles in an attempt to prevent pine needle induced abortions would need to be continuously administered in order to maintain the necessary microbial composition in the rumen. Further research is needed to more fully characterize the microbiome changes that occur during pine needle exposure and to understand how those changes can be safely initiated and maintained in order to potentially prevent pine needle-induced abortions in cattle.
Technical Abstract: Consumption of ponderosa pine needles, as well as needles and bark from a number of other trees, can cause abortions in cattle. The abortifacient compounds in these trees are labdane resin acids, including isocupressic acid and agathic acid. Previous research has demonstrated that cattle conditioned to pine needles metabolize the labdane resin acids more quickly than naïve cattle. The results from that study indicated that changes had occurred in the rumen of conditioned cattle. Therefore, in this study, the changes that occurred in the rumen bacterial microflora of cattle during exposure to ponderosa pine needles were evaluated. Cattle were dosed with ground pine needles twice daily for 7 d. Rumen samples were collected on d 0, 3, 7, and 14 (7 d after treatment stopped) and ruminal bacterial microbiome analyses were performed. There were 372 different genera of bacteria identified in the rumen samples. Principal coordinate analysis indicated that there was a significant difference in the rumen bacterial composition between the time points. There were 18 genera that increased in abundance from d 0 to d 7. Twenty three genera decreased in abundance from d 0 to d 7. The results from this study demonstrated that exposure of cattle to pine needles caused a clear shift in the rumen microbiome composition. In general, this shift lasted less than 1 week post exposure, which indicates that any prophylactic treatment to manipulate the ruminal metabolism of the abortifacient compounds in pine needles would need to be continuously administered in order to maintain the necessary microbial composition in the rumen.