Thursday, September 1, 2016

Quantifying cattle diet across broad gradients

Just a quick note on a new paper that we just published.

I've worked before with Texas A&M's GANLab to assess patterns across the US of forage quality for cattle. In that paper, we saw that cattle in cool, wet regions had the highest forage quality, which suggested the warming would reduce forage quality. It was an important paper for understanding how global warming would affect the ability of grassland to sustain grazers.

Although that work showed geographic patterns of forage quality, we couldn't tell how the species that the cattle consumed might be changing.

Just this month, we published a new paper where we sequenced the plant DNA in fecal samples of cattle across the US to answer that question.

Those results are pretty interesting, too.

In short, cattle in warmer grasslands are relying more on forbs than cattle in cooler grasslands. That suggests warming will shift the diet of cattle, potentially to compensate for lower forage quality. This is pretty similar to what we saw for bison.

The specific results are important, but the general approach is even more interesting. This is the first time the diet of an herbivore was quantified over such a large spatial scale and with such specificity. For example, we could see the species of grasses shift as one moved south, and the unique diet of cattle in southern Texas (a fair amount of live oak there).

1 comment:

  1. Joe, interesting post and interesting paper. Coincidentally, we have a paper on forage quality of big blue from IL to CO coming out soon in Grassland Science. Strong gradients in forage quality with a decline from west to east. But, a greenhouse study on plants grown from seed suggests that forage quality of the eastern (IL) ecotype may be more resilient to changes in soil moisture that may occur in response to climate change. I can send proofs if you're interested. Best wishes, David