Animal health and welfare are important components of social sustainability. In the beef industry, bovine respiratory disease complex is likely the largest issue, and also influences antimicrobial stewardship. Nutritional stress when adapting cattle to high grain diets occurs in the form of subacute acidosis predisposing cattle to other health challenges such as bovine respiratory disease. Acidosis occurs from overproduction of lactic acid from rapid fermentation of starch, and the slow adaptation of cattle to a high grain finishing diet is necessary to allow the population of lactic acid utilizing bacteria in the rumen that keep the lactic acid concentration low and rumen pH high.  Subacute rumen acidosis has been linked to the release of lipopolysaccharides from dead bacteria causing inflammation that may predispose cattle to other health issues. Early bovine respiratory disease research indicates that high concentrate starting diets and lack of adequate roughage intake during the receiving period, both of which could result in subacute rumen acidosis, increase the incidence of respiratory disease.

A major lactic acid utilizing bacteria in the rumen is megasphaera elsdenii.  Inoculation of cattle with M. elsdenii when introducing a high starch diet, stabilizes rumen pH, prevents subacute rumen acidosis, and allows stepping cattle up to the finishing diet quicker. Additionally, inoculation of feedlot cattle on arrival can reduce respiratory morbidity, particularly in higher-risk calves, although the number of studies is limited (Figure 1).  Clinical signs of rumen acidosis and respiratory disease are somewhat similar and misdiagnosis can occur. Thus, the reduction in respiratory morbidity could be those calves with rumen acidosis being misdiagnosed as bovine respiratory disease.  But either way, inoculation of cattle with M. elsdenii at arrival can reduce animal disease and antimicrobial use. Nutritional technology plays a role in animal health-improving antimicrobial stewardship and social sustainability.

Figure 1. Prevalence of bovine respiratory disease in calves (1 study) or yearlings (2 studies) receiving megaspheara elsdenii orally at arrival (ME) or not (Control). Data from McDaniel (2009; and Miller et al. (2013; Bovine Practictioner 47:137)