Nutritional Management for animal health
The effect of infections and other illnesses on the nutritional status of an animal depends on the type and severity of the illness, initial nutritional status of the animal, and more importantly, the feed intake during illness. Accordingly, appropriate nutrition is vital to early restoration of normal health of a diseased animal.
Dr Ashok Kumar Pattanaik and Dr Kusumakar Sharma
Feeding and nutrition of farm animals have traditionally been linked to productivity. It is an accepted fact that improved feeding management is the mainstay of all approaches that aims to augment production from food animals. However, more recently, the developments in the field of food bio-science have brought to the fore the important role nutrition can play in ensuring health and wellbeing. It is being increasingly clear through advanced clinical nutrition research that food plays a central role in optimal health, and strategic use of specific feed ingredients and diets can have profound impact on the animal health. While many of the emerging concepts on the potential use of specific nutrients and nutraceuticals for prevention and/or therapeutic management of diverse diseases have their origin for human application, the same can have wide-ranging applications in managing the health and wellbeing of farm and companion animals as well. However, while dietetics or nutritional management has always been an integral part of the disease management in human medicine, the same is not yet true for veterinary practice, especially in farm animal medicine.
Nutrition for health
In large animals clinical nutrition as a subject of research and/or practice has hardly moved beyond the confines of deficiency- and metabolic-diseases. Nutritional management of sick animals has always been a challenging task in veterinary medicine. While therapeutic approaches remain the mainstay for ensuring the recovery of animals suffering from any disease condition, appropriate feeding management of clinically ill animals is often not given its due importance. However, it is fast becoming an integral part of the veterinary medicine with the increasing recognition of clinical nutrition as an essential facet of therapeutic management of suffering of animals from various diseases.
The subject of feeding of sick animals is as diverse as the type of diseases the farm animals suffer. Hence, dealing with the practical feeding management of clinically ill animals could be too big a subject. What is more important is the basis of deciding the appropriate approach in the nutritional management of sick animals. Hence, a proper understanding of the mechanism of metabolic (nutritional) alterations occurring during various types of disease conditions paves way for deciding the nutritional regimen to be adopted for managing a disease.
The concept of applying nutrition as a tool for health has two major components: (i) study of various aspects of nutrient metabolism in animals suffering from specific clinical affections, with a view to utilize the knowledge for defining the role of specific nutrient(s) in the treatment and/or prevention of that particular disease, and (ii) utilization of existing knowledge on the role of specific nutrient(s) in prevention of metabolic disorders and reducing the incidences and/or severity of infectious diseases through improved defense and antioxidant status.
Consequence of disease on host nutrition
Recent research has demonstrated that endemic diseases negatively impact livestock performance without causing obvious clinical signs of disease. Infectious agents induce an immune response designed to remove the offending agent from the body. In turn, the immune system induces a cascade of effects, many of them detrimental to growth, on the animal’s metabolic system. It is therefore suggested that technologies that minimize activation of the animal’s immune system will enhance the rate and efficiency of growth and improve lean deposition in the carcass. It has been established that during a health challenge, immune substances cause a metabolic response to the infection that shifts nutrients away from tissue growth to support the immune response. Even when the challenge is subclinical in nature, the effect is sufficient to disrupt normal metabolism and cause losses in performance. Exposure of an animal to any substance, pathogenic or nonpathogenic, results in an immune response from the inflammatory cells in the blood and tissues. The substances that are released activate the immune system, causing reduced appetite, an increase in basal metabolic rate, a shift in the use of both ingested and stored nutrients by the body, and the possibility of a slight elevation in body temperature. However, sometimes there is no obvious sign that disease is present.
When animals are challenged by disease, protein synthesis decreases while protein breakdown increases. The balance between synthesis and breakdown shifts toward breakdown as a result of at least three things: (a) reduced feed intake – the body’s supplies of amino acids are gradually consumed as the body’s defenses fight the infection, (b) the immune response requires the consumption of amino acids to provide the building blocks to make immune compounds, like antibodies, and (c) the amino acid composition of muscle does not match the amino acid needs of immune products, so the body is forced to break down a disproportionate amount of muscle to meet the amino acids needs of the immune system.
Therefore, protein losses during an infection are greater than what can be maintained by feed intake. Research in other animals has shown that the body can initiate protein breakdown to pull nutrients from tissues having a lower priority, making them available for use by the immune system. In essence, the body will literally consume itself in the process of prioritizing resources in its fight against pathogens. In addition to effects on protein synthesis, the processes initiated by an immune challenge also cause major shifts in fat metabolism. Typically, as energy is consumed during periods of immune activation, fat reserves are broken down as a source of energy to feed the immune system. As a consequence of the metabolic and physiological effects of disease, animals endemically infected with disease agents suffer from poorer growth performance, as reflected in reduced average daily feed intake, average daily gain, and feed efficiency. All pathogens that cause an immune response have the potential to disrupt metabolic processes and interfere with nutrient utilization.
Role of nutrition in disease management and recovery
Most diseases and disease conditions can be affected by diet. For some conditions and diseases this may simply be related to the adverse effects of inadequate caloric intake associated with hyporexia or anorexia of illness. For many other conditions and diseases, there are specific nutritional management interventions. Feeding of diseased animals should be based on their nutritional requirements while giving due importance to their natural diet and feeding behaviour. Further, adequate consideration should also be given to the frequency of feeding. Disease-affected animals often have a decreased appetite and weight loss; hence palatability is one of the most important factors deciding the effectiveness of the diet. The quality of the ingredients chosen is also of immense importance. Highly digestible ingredients compensate for the decreased activity of intestinal enzymes, ensuring an optimal nutrient supply.
In order to overcome poor appetite, there are several feed additives that can be administered including vitamin B-complex boluses, dried brewer’s yeast, or live cell yeast / Aspergillus oryzae, or feeding sodium bicarbonate. The animal can be encouraged to consume different forages like straw, calf starter, cereal grains. Encourage forage intake over concentrates. Alternatively, rumen bypass protein or protected amino acids may also be tried. Essential nutrients which help faster recovery from illness in livestock and pets are protein, fats and carbohydrates (energy) and micro nutrients. Proteins are the major building blocks in the repair process and are important in maintaining the immune system. Protein requirements of the diseased and convalescing animals are usually higher than for the normal maintenance. An increased protein level promotes restoration of lean body mass and increases palatability during the post operative period. Feeding of higher levels of good quality protein promotes wound healing.
Fats and carbohydrates are excellent sources of energy, which is needed in larger amounts than normal for repairing the tissues affected by illness, injury or surgery and to fight infection. Increasing the fat level of the diet provides a more ‘concentrated’ food (calorie-dense) so that the animal can receive the higher levels of energy and other nutrients needed in a smaller amount of food. In most circumstances the amount of energy required per day is greater than the basal or maintenance energy requirement by the species. Fats and omega-3 fatty acids help to manage inflammation. Omega-3 long chain fatty acids help maintain joint mobility, skin health and digestion. In addition to protein and energy, certain minerals and vitamins have important roles to play in the healing process. Diets designed for diseased animals must have the correct balance of minerals and vitamins to avoid the depletion of body stores and provide those needed for the period of recovery. Zinc and potassium improve wound healing. Vitamin B complex improves digestive (microbial) efficiency.
Besides, there are many other nutraceuticals available commercially including herbal metabolic modifiers, antioxidant blends, prebiotics, and probiotics, etc. which could also be used as supplements/additives to augment the digestive capability and thereby invigorating the animal. The synergistic antioxidant complex (vitamin E, vitamin C, taurine and lutein) helps neutralize free radicals produced during body metabolism and promotes good health.
There is little published information available on convalescent diets suitable for farm animal species. However, a decision on the nature and quality of the diet could be taken based on the following principles.
- Adequate nutrition of clinically ill animals is best ensured by understanding their requirements vis-à-vis availability of desired ingredients.
- Feeding management should invariably take into account the requirement for additional nutrients for healing as well as maintenance needs.
- Any nutritional deficiencies at this stage may increase the susceptibility to infectious disease/re-infection. Care should be taken not to under- or over-supplement the diets with vitamins and minerals.
- The food should be of high quality in terms of palatability and digestibility. The natural diet should be considered when deciding on suitable ingredients.
- Consumption of food should be monitored on a real-time basis. Monitoring of body weight and condition is important for animals reared under group feeding system.
- Careful and rationale use of proprietary products suitable for convalescing animals may prove useful for accelerated recovery.
In general, illnesses in livestock are usually associated with reduced appetite and decreased feed consumption. The effect of infections and other illnesses on the nutritional status of an animal depends on the type and severity of the illness, initial nutritional status of the animal, and more importantly, the feed intake during illness. Accordingly, appropriate nutrition is vital to early restoration of normal health of a diseased animal. More importantly, from the production animal point of view it is one of the key health approaches for increasing/make good the loss in the productivity. While the concept is well established in pet animal practice, its application in large animal practice is still not widely adopted. However, with the changed perspective of livestock production with a focus on feed-food safety and animal welfare, the concept of specialized nutrition of diseased animals could find its place in farm animal practice in the time to come.
( Dr Pattanaik is Principal Scientist, Clinical & Pet Nutrition Laboratory, Division of Animal Nutrition, ICAR-Indian Veterinary Research Institute, Izatnagar. Dr. Sharma is Consultant, RLB Central Agricultural University, Jhansi. Views expressed are personal.)