Submitted to: International Symposium on Poisonous Plants
Publication Type: Book / Chapter
Publication Acceptance Date: 8/24/2001
Publication Date: 11/20/2003
Citation: Anderson, T.J., Anderson, R.C., Williams, M.J., Elder, R.O., Nisbet, D.J. 2003. PCR amplification for detection of Synergistes jonesii, the ruminal bacterium that degrades the toxins of Leucaena leucocephala. In: Acamovic, T., Stewart, C.S., Pennycott, T.W., editors. Poisonous Plants and Related Toxins. Cambridge, MA: CABI Publishing. p. 223-226.
Interpretive Summary: Leucaena is a high quality hardy plant that, because of its drought tolerance and disease resistance, has great potential to be used as a forage by Texas ranchers. Unfortunately, the plant contains toxins that under certain conditions can poison the animals eating it. Some cattle, sheep and goats contain a beneficial gut bacterium, Synergistes jonesii, that can degrade the plant toxins thus allowing the animals to safely consume the plant. However, the bacterium is present at low numbers or is absent in some animals, which places these animals at risk to poisoning. Therefore, ranchers need to know the S. jonesii colonization status of their animals in order to safely manage leucaena use on their ranches. Because the present method for detecting S. jonesii takes months to complete, we wanted to test the use of a more rapid state-of-the-art DNA based procedure to check whether or not an animal is colonized by the beneficial bacterium. We found that while the method was not very good at detecting the presence of the bacterium in feces, it was very good at detecting very small amounts of the bacterium in saliva or stomach contents. These results provide important information to help Texas ranchers safely graze their animals on leucaena thus helping them to produce the highest quality, lowest cost meat products for the American consumer.
Technical Abstract: Leucaena leucocephala is a drought tolerant legume containing toxins that restricts its use as a forage. Ruminants colonized naturally or intentionally with sufficient numbers of Synergistes jonesii, a beneficial rumen bacterium capable of detoxifying the toxins, can safely consume diets containing >50% leucaena. However, the microbe may be at low numbers or absent in ruminants not consuming leucaena, thus placing these animals at risk to poisoning upon their next exposure to the plant. Consequently, livestock producers need to know the whether or not their animals are colonized by sufficient numbers of S.jonesii in order to safely manage leucaena use on their ranches. Because the present method for culturing S. jonesii takes months to complete, we assessed the feasibility of using a more rapid polymerase chain reaction (PCR) method. Using purified DNA and primers specific to a non-homologous piece of S. jonesii DNA, S. jonesii could be detected at a level of 1.2 pg DNA. The specificity of the primers was confirmed when no PCR product was generated from bacterial DNA prepared from rumen, fecal, and saliva samples from cattle never exposed to leuceana. In all cases, S. jonesii could be detected from these samples when spiked with 1 ul of a pure culture of S. jonesii; however, the sensitivity was much better with rumen fluid and saliva than with feces. Synergistes jonesii was detected in rumen contents from a cow known to be colonized with S. jonesii (culture positive); however, detection of S. jonesii in feces was not reliable by either culture or PCR method.