PHYSIOLOGICAL-CHANGES AT PARTURITION AND THEIR RELATIONSHIP TO METABOLIC DISORDERS

Most of the metabolic diseases of dairy cows-milk fever, ketosis, reta ined placenta, and displacement of the abomasum-occur within the first 2 wk of lactation. The etiology of many of those metabolic diseases t hat are not clinically apparent during the first 2 wk of lactation, su ch as laminitis, can be traced back to insults that occurred during ea rly lactation. In addition to metabolic disease, the overwhelming majo rity of infectious disease, in particular mastitis, becomes clinically apparent during the first 2 wk of lactation. Three basic physiologica l functions must be maintained during the periparturient period if dis ease is to be avoided: adaptation of the rumen to lactation diets that are high in energy density, maintenance of normocalcemia, and mainten ance of a strong immune system. The incidence of both metabolic and in fectious diseases is greatly increased whenever one or more of these p hysiological functions are impaired. This paper discusses the etiologi cal role of each of these factors in the development of common disease s encountered during the periparturient period.