Sunday, October 1, 2017

October science journal article summary


Here's some science to make your October outstanding! I have a 3-question survey about these summaries that should take a minute or less to answer; please consider taking it (or emailing me if you prefer). I'm trying to get a sense of how often people read them, whether the level of detail is right or not, and get any other feedback people have:

The focus of this review is on reducing the impacts of animal agriculture (especially cattle). For anyone who missed my June 2016 review, I'll re-recommend Herrero et al 2016 as a fantastic overview of the potential for improving GHG emissions in the livestock sector. Their top picks were improved feed digestibility (including more cereals, distiller's grains, etc. to supplement or replace grass and hay), feed additives, avoiding land use change through intensification, and carbon sequestration from better grazing.

There a lot of discussion on how to shrink the high carbon footprint of cattle (beef and dairy), and one focal area is on enteric methane (mainly cow burps). Hristov et al 2015 is a study showing that a feed additive (3NOP) was able to reduce dairy methane production by ~30% (with oddly similar impact regardless of the dose) without substantially affecting milk yield (although it increased weight gain by 80% over the 12 week period). This is a relatively small study (48 cows) and it would be see what the impact is throughout the life of dairy cattle (as often gut flora adapts to these kinds of additives over time), but this combined with a couple of similar studies they cite are exciting enough to be worth recommending more trails and pilots.

Kinley et al 2016 is a similar paper looking at a different feed additive (this one based on seaweed). This is only an in vitro study (messing with petri dishes rather than actual cows) but they found adding doses of 2% or greater to a grass diet virtually eliminated methane production. Note that a very similar paper (Machado et al 2015) had similar results, but with two key differences: they saw a strong benefit at 1% dose (where Kinley had a weaker response at that dose), and they also saw some side effects that could impact cattle health at 2% and above. While this was only in vitro and only tested for 3 days, it's still worth investigating and comparing to 3NOP for efficacy and potential positive and negative side effects.

Swain et al 2018 (it came out online early) is a paper from the Breakthrough Institute arguing for a shift to more intensive livestock systems, especially switching from grass-finished to grain-finished beef. They make a number of good points; it's not really debatable that feedlot cattle require less land and time, and most scientists agree the GHG emissions are lower per unit of meat in feedlot systems as well. They briefly discuss some of the potential tradeoffs including animal welfare and antibiotic use and how they might be addressed, and the issue of how to ensure that higher productivity actually leads to land sparing as opposed to driving more habitat conversion. While a good read, there are a few things they don't cover that should also be part of the conversation. One is that in some cases we may actually prefer a high land use footprint, if the grazing lands are high-quality natural grasslands that would otherwise be converted to other uses. But it's still a worthwhile read with good food for thought.

Odadi et al. 2017 (authored by a NatureNet fellow, along with TNC's Joe Fargione) looks at the impact of planned grazing (focus on intensive rotational grazing, but including several other factors) on a variety of outcomes in Kenya. They found substantial improvements in vegetation (cover, species richness and diversity, etc.), presence and richness of wildlife, cattle weight gain during dry periods when they were in poor condition, and the amount of cattle supported per unit of land area. The cool thing to highlight here is that they were able to improve cattle condition as well as wildlife habitat. One critical ingredient to success was more active involvement from pastoralists; this does mean more effort for them but it appears that the benefits make it worth promoting.


Remember the synthesis of evidence for how several agricultural practices impact a suite of outcomes that Rodd Kelsey led (I sent it out last month)? This month I'm sharing one more 2-page document, which has a great chart summarizing the evidence for each of the practices evaluated on each of the outcomes. If you want to explore more deeply, you can do so at[]=22

Herrero, M., Conant, R., Havlik, P., Hristov, A. N., Smith, P., Gerber, P., … Thornton, P. K. (2016). Greenhouse gas mitigation potentials in the livestock sector. Nature Climate Change, 6(May), 452–461.

Hristov, A. N., Oh, J., Giallongo, F., Frederick, T. W., Harper, M. T., Weeks, H. L., … Duval, S. (2015). An inhibitor persistently decreased enteric methane emission from dairy cows with no negative effect on milk production. Proceedings of the National Academy of Sciences of the United States of America, 112(34), 10663–10668.

Kinley, R. D., De Nys, R., Vucko, M. J., MacHado, L., & Tomkins, N. W. (2016). The red macroalgae Asparagopsis taxiformis is a potent natural antimethanogenic that reduces methane production during in vitro fermentation with rumen fluid. Animal Production Science, 56(3), 282–289.

Machado, L., Magnusson, M., Paul, N. A., Kinley, R., de Nys, R., & Tomkins, N. (2016). Dose-response effects of Asparagopsis taxiformis and Oedogonium sp. on in vitro fermentation and methane production. Journal of Applied Phycology, 28(2), 1443–1452.

Odadi, W. O., Fargione, J., & Rubenstein, D. I. (2017). Vegetation, Wildlife, and Livestock Responses to Planned Grazing Management in an African Pastoral Landscape. Land Degradation and Development, (March).

Swain, M., Blomqvist, L., McNamara, J., & Ripple, W. J. (2018). Reducing the environmental impact of global diets. Science of the Total Environment, 610–611, 1207–1209.

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