The production diseases, which were previously referred as metabolic diseases, include diseases like parturient paresis (milk fever), downer cow syndrome, fat cow syndrome, ketosis, acute hypokalemia, hypomagnesemic tetanies (lactation tetany, grass tetany and grass staggers), neonatal hypoglycemia and post-parturient haemoglobinuria. The diseases such as steatites, low milk fat syndrome, equine Cushing's disease, equine hyperlipidemia and lactation tetany in mare are also included in production disease group. Amongst all farm animals, the production diseases assume greatest significance in dairy cows and buffaloes. The occurrence of production diseases is attributed to an imbalance between the rates of 'input' of dietary nutrients and 'output' of production. Persisting imbalance leads to depletion of reserves of certain metabolites or their throughput giving rise to signs of production diseases. Classic examples of the outcome of the process are ketosis caused by hypoglycemia, tetanies caused by hypomagnesaemia and milk fever caused partly due to hypocalcaemia. These are also referred as metabolic diseases as imbalance in certain nutrients results in variation of some body's metabolites leading to the development of metabolic disorders.
The incidence of production diseases is highest in the period beginning at calving till the peak of lactation. In terms of input and output, a dairy cow or buffalo is like an industrial system, but at the same time it has a biologically inherent defect which is not shared by industry. In case of industry, decrease of input will automatically reduce the output, whereas for dairy animals, the production receives priority even though animal suffers from disease. Under the stress of higher production system, there is relatively high turnover of fluids, salts and soluble materials. Sudden variation in excretion or secretion of sodium, potassium, calcium, phosphorous, magnesium, chloride, etc in the milk or by other tissues and sudden change in their intake due to altered ingestion, digestion or absorption may cause disruption in the internal environment of the animal. The additional nutritional demand during pregnancy or lactation is exacerbated by a sub-optimal nutrient supply during dry period leading to high incidences of production diseases.
Sudden onset of profuse lactation after parturition in high yielding dairy animals may further reduce the already depleted essential metabolite to a level at which production diseases such as milk fever, lactation tetany or ketosis can occur. The hormonal stimulation in early lactation is so strong that even with nutrients' deficiency, serious drain of metabolites occurs via milk production. Further, antioxidant system in the body is also at stress during periparturient and early lactation periods. It is reported that plasma a- tocopherol (vitamin E), the major lipid soluble antioxidant is at the lowest level during this period and there are possibilities of excess reactive oxygen species (ROS) leading to oxidative stress and associated metabolic changes. The breed, age, season and management practices are also important predisposing factors to production diseases. Jersey cows are more susceptible to milk fever than other breeds and Guernsey breed is more susceptible to ketosis. Though definite reasons of this variation are yet to be ascertained, factors such as lesser receptors for 1, 25- dihydroxy cholecalciferol (vitamin D3) in the intestine of some breeds of cattle has been proposed to be responsible for milk fever. Age wise, production diseases occur more frequently during or after third lactation.
The management of metabolic and deficiency diseases has been possible to some extent by forecasting occurrence of these diseases by using modern tools such as Compton metabolic profile test, micro-mineral profile of soil-plant- animal and by using specific preventive approaches such as calcium gel therapy, hormonal therapy, and use of suitable mineral mixture at the appropriate time of the production cycle.