These short grasses can have roots that extend 1 m (about 3 ft) deep. The height of grass correlates with the amount of rainfall it receives. Grasslands receive about 500 to 900 mm of rain per year compared to deserts, which receive less than 300 mm and tropical forests, which receive more than 2,000 mm. While temperatures are often extreme in some grasslands, the average temperatures are about -20Â°C to 30Â°C.
The use of antimicrobials has been linked to the rise of resistance in every drug and species where it has been studied, including humans and livestock. However, the role of antibiotic use in food animals â in contrast to the use of antibiotics in humans â in the rise of resistant infections in humans is in dispute.
The 1981 CAST report, Antibiotics in Animal Feeds, stated that, up to that point, there were only 4 instances (2 in Britain, 1 in Canada, and 1 in the United States) for which there was âevidence linking use of antibiotics in animal agriculture with diseases due to antibiotic-resistant bacteria in humansâ (p. 2), and it attributed the incidents to therapeutic rather than subtherapeutic use of antibiotics.