Metabolic disorders of cattle.

Goldberger discovered human pellagra was a non-infectious disease, affecting mostly the small and the timid in overcrowded institutions. Symptoms were diarrhoea, dermatitis and dementia. The staff and older children escaped the disease. They ate the meat and left the small and timid with the gravy. The 'Goldberger syndrome' is observed during competitive feeding of livestock, in ketotic animals and in the zinc depleted which are lethargic and pick all day at their feed. The pellagra preventative factor was later found to be nicotinic acid, derived from the amino acid tryptophan. Deficiencies of copper, magnesium, vitamin B6 (activated by a zinc kinase) inhibit the conversion of tryptophan to nicotinic acid. Stresses, including liver diseases, malabsorption, iron overload, porphyria, marasmus, cold stress, pregnancy, lactation, antibiotics and sulfa drugs, all increase dietary needs of nicotinic acid. Elevated free fatty acids and ketone bodies in the blood are associated with ketosis, zinc depletion and the pre-diabetic state. There is a diminished uptake of glucose by the tissues, a condition also found in parturient paresis of dairy cows when elevated hydrocortisone promotes insulin resistance and hyperglycaemia. This defect in insulin response leads to a diabetic-like state. The major predisposing factor in parturient paresis of dairy cows is hypocalcaemia. Gut absorption of dietary calcium may not meet the primary demands of lactation initiation until bone calcium mobilisation is established.