Co-grazing of cattle and sheep weakens the diet selectivity of cattle

Diet selectivity of domestic herbivores is a key factor influencing plant community structure and grassland ecosystem functions. However, it remains unclear how different livestock species interact to influence their diet selectivity. Here, we experimentally assessed the effects of two common livestock species, cattle and sheep, on each other’s diet selectivity by grazing them alone and together on a meadow steppe. Results showed that cattle as the larger-bodied herbivores did not affect the diet selectivity of sheep, while the presence of sheep significantly reduced that of cattle. The reduced diet selectivity of cattle was due to their forage displacement driven by competition from sheep. Both herbivores exhibited a strong selection for legumes, which are non-dominant plants in the community, when grazing alone. However, grazing together with sheep forced cattle to decrease their selection for legumes and increase their selection for the dominant grass (Leymus chinensis). Furthermore, the presence of sheep led to fewer traveling steps for cattle. Our study highlights that the co-grazing of cattle and sheep weakens the diet selectivity of cattle. Thus, we suggest that co-grazing of cattle and sheep may be a more effective grazing regime for grassland conservation and sustainable utilization.