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NUTRITIONAL EFFECTS ON IMMUNOLOGY AND INFLAMMATION IN DAIRY CATTLE
Optimal health is of paramount importance for an acceptable life of farm animals, mainly during the pivotal phases of their life cycle such as parturition and weaning. Nutrition is one of the most important players of the health status, and can influence onset of clinical diseases or mild malaise (subclinical diseases). A large portion of the host resistance to infection involves the immune system and, mainly at the gastro-intestinal level, represents a crucial site of the body for the relationship among nutrients, microbes and host. Balanced diets guarantee that nutrient requirements are met and simultaneously can: i) counteract the survival of infectious pathogens in the gastro-intestinal tract (as occurs with diets too high in fermentable carbohydrates), ii) prevent damage of the gut epithelium, iii) improve the host resistance to the pathogens, iv) reduce tissue damage due to metabolic disorders associated with deficiencies (e.g. ketosis, liver lipidosis) and excesses (e.g. milk fever, obesity) of nutrients. A wide variety of nutritional compounds (e.g. macro and micro-nutrients, secondary metabolites of plants) are involved in aspects of immuno-regulation, but mechanisms are only partly known. The physiological conditions of the animals also play a relevant role in the regulatory effects of the nutrients on immune and metabolic systems. In dairy cows, the transition period represents the most vulnerable physiological life stage, in which the nutrition can influence the immune and inflammatory responses. The tremendous physiologic changes taking place during this period make the diagnosis of the nutritional-management causes challenging. Nevertheless, the immune-metabolic profiling appears as a valuable tool in the management of health of transition dairy cows, particularly for direct diagnosis of sub-clinical diseases (metabolic and infectious). Recently, growing evidence suggests that inflammation around calving is responsible for reduced performance and is associated with decreased production, efficiency and fertility. In particular, composite indices based on multiple variables associated with inflammation (e.g. Liver Functionality Index) are promising for use as an aid in the diagnosis and correction of management and nutritional problems on dairy farms. Nutritional improvements in the periparturient period not only reduce the frequency of inflammatory events, but also minimize their intensity and duration. In particular, some nutrients and compounds (e.g. omega-3 fatty acids, Conjugated Linoleic Acid, methionine, plant extracts) have demonstrated to improve the immune function and the inflammatory response around calving, underscoring a need for further studies of the interactions between nutrition, immunity and inflammatory response.
Keywords: nutrition, immunology, transition cow