Data from: Continental-scale patterns reveal potential for warming-induced shifts in cattle diet

In North America, it has been shown that cattle in warmer, drier
grasslands have lower quality diets than those cattle grazing cooler,
wetter grasslands, which suggests warming will increase nutritional stress
and reduce weight gain. Yet, little is known about how the plant species
that comprise cattle diets change across these gradients and whether these
shifts in dietary quality coincide with shifts in dietary composition,
i.e. the relative abundance of different plant species consumed by cattle.
To quantify geographic patterns in dietary composition, we analyzed the
dietary composition and dietary quality of unsupplemented cattle from 289
sites across the central US by sequence-based analyses of plant DNA
isolated from cattle fecal samples. Overall, assuming that the percentage
of reads for a species in a sample corresponds to the percentage of
protein derived from the species, only 45% of the protein intake for
cattle was derived from grasses. Within the Great Plains, northern cattle
relied more on grasses than southern cattle, which derived a greater
proportion of their protein from herbaceous and woody eudicots. Eastern
cattle were also more likely to consume a unique assemblage of plant
species than western cattle. High dietary protein was not strongly tied to
consumption of any specific plant species, which suggests that efforts to
promote individual plant species may not easily remedy protein
deficiencies. A few plant species were consistently associated with lower
quality diets. For example, the diets of cattle with high amounts of
Elymus or Hesperostipa were more likely to have lower crude protein
concentrations than diets with less of these grasses. Overall, our
analyses suggest that climatic warming will increase the reliance of
cattle on eudicots as protein concentrations of grasses decline.
Monitoring cattle diet with this DNA-based sequencing approach can be an
effective tool for quantifying cattle diet to better increase animal
performance and guide mitigation strategies to changing climates.