Grassland saline-alkaline degradation-induced excessive iron and sodium
intake potentially increases the transmission risk of fecal pathogenic
bacteria in cattle
Abstract
Although grassland degradation is well known to increase the pathogenic
bacteria abundance that live on and in the plants and soil, whether
grassland degradation would further increase the fecal pathogenic
bacteria in herbivore, and thus increasing the risk of animal and human
diseases via environmental pollution, still remains elusive. Here, we
investigated the effects of grassland saline-alkaline degradation on the
fecal pathogenic bacteria of domestic ruminant-cattle, and also
preliminarily explored the underlying mechanisms of influence via
analyzing changes in nutrient intake from cattle that long-term grazing
on undegraded and severely degraded grasslands, respectively. Our
results showed that the relative abundance of pathogenic bacteria
including Streptococcus, Mogibacterium and
Alistipes were increased significantly in the cattle grazing on
severely degraded grassland. Notably, the results for correlation
analyses demonstrated that the Paludibacter had a positive effect
on these three pathogenic bacteria. Moreover, we found that cattle
grazing on severely degraded grassland showed an increased iron and
sodium intake compared with those cattle grazing on undegraded
grassland. Further, our results found that the Fe intake most contribute
to the enhancement of the relative abundance of fecal
Streptococcus and Paludibacter, whilst the Na intake most
contribute to the increase in the relative abundance of fecal
Alistipes. In general, our study highlights that Fe and Na intake
could mainly affect the abundance of fecal pathogenic bacteria in cattle
through two pathways, namely direct as well as indirect regulation of
Paludibacter abundance. Our findings suggest that increasing
grassland saline-alkaline degradation worldwide will not only greatly
increases the risk of animal diseases, but also even poses a serious
threat to human health through environmentally mediated transmission,
and therefore, cattle grazing on severely degraded grassland should be
prohibited.