Recently Pollan was on Oprah, spouting his oft-repeated line that corn is not a natural food source for cows (and ruminants) and that we are force-feeding the foodstuff causing them to become sick.
According to Pollan, in order to feed cattle corn, we have to also feed them antibiotics.
For most farmers, that statement is so laughable they can't believe someone would actually believe it. In fact, most don't think it is worth a response.
Liver abscesses in slaughtered beef cattle result from aggressive grain-feeding programs. The incidence, averaging from 12 to 32% in most feedlots, is influenced by a number of dietary and management factors. Liver abscesses represent a major economic liability to producers, packers, and ultimately consumers. Besides liver condemnation, economic impacts include reduced feed intake, reduced weight gain, decreased feed efficiency, and decreased carcass yield. Fusobacterium necrophorum, a member of the ruminal anaerobic bacterial flora, is the primary etiologic agent. Actinomyces pyogenes is the second most frequently isolated pathogen. Ruminal lesions resulting from acidosis generally are accepted as the predisposing factors for liver abscesses. F. necrophorum possesses or produces a number of virulence factors that participate in the penetration and colonization of the ruminal epithelium and subsequent entry and establishment of infection in the liver. However, only a few virulence factors have been characterized well. Control of liver abscesses in feedlot cattle generally has depended on the use of antimicrobial compounds. Five antibiotics (i.e., bacitracin methylene disalicylate, chlortetracycline, oxytetracycline, tylosin, and virginiamycin) are approved for prevention of liver abscesses in feedlot cattle. Tylosin is the most effective and the most commonly used feed additive. Tylosin feeding reduces abscess incidence by 40 to 70%. The mode of action of antibiotics in preventing liver abscesses is believed to be via inhibition of ruminal F. necrophorum. Protective immunity against F. necrophorum induced by a variety of antigenic components has ranged from ineffectual to significant protection.
Liver abscesses are seen in all ages and breeds of cattle wherever cattle are raised. They are most common in feedlot and dairy cattle fed rations that predispose to rumenitis.
Liver condemnation rates as high as 40% were recorded in a large survey of cattle slaughtered in the USA.
Tylosin phosphate fed at 10 g/ton of feed significantly reduces the number of liver abscesses and increases feed efficiency and weight gain but has little, if any, effect on prevalence of ruminal lesions. Virginiamycin fed at 16 g/ton of feed or chlortetracycline fed continuously at 70 mg/head/day during the finishing period is also used.