<p>Hammond K. J., Muetzel S., Waghorn G. C., Pinaes-Pati&ntilde;o C. S., Burke J. L., Hoskin S. O. 2009. The variation in methane emissions from sheep and cattle is not explained by the chemical composition of ryegrass. Proceedings of the New Zealand Society of Animal Production, 69, 174-178.</p>
<p><strong><a href="http://www.nzsap.org/proceedings/2009/variation-methane-emissions-sheep-and-cattle-not-explained-chemical-composition">Read more </a></strong>(external link)&nbsp;</p>