Senwes Scenario December 2018 / January 2019 | Page 24

AGRICULTURAL 21 | Nutrition and Immunity of Feedlot Cattle cy. An extreme immune response not only wastes resources but may cause local cell damage and depress productivity. WHAT IS THE EFFECT OF NUTRITIONAL STATUS ON RESISTANCE TO INFECTION? Good nutrition improves disease resis- tance of stressed cattle, by helping to counteract the suppression of the immune system caused by stress hormones and by providing nutrients essential for main- taining and activating the immune system as required. Generally, nutrition has most impact on health during the first month on feed and particularly for highly-stressed or lighter weight cattle. Many of the cattle entering feedlots are marginally deficient in several trace minerals, especially if they previous­ ly grazed dormant native range or pas- ture. Receiving rations should be ade- quately supplemented with trace minerals, vitamin A and vitamin E. Feeding higher levels than normal of these nutrients in the receiving period can compensate for reduced intake and marginal deficiencies on arrival. After cattle have recovered from stress induced immune suppression and are adapted to the finishing diet, balancing feedlot diets to meet requirements for growth usually provides adequate nutrients for immune function. In order of priorities, providing a palat- able diet on arrival and encouraging feed and water consumption is most important. There is little benefit from adding expen- sive nutrients to an unpalatable diet. Research has shown that it can take up to a week or more for all calves in a pen to consistently consume some feed within a single day. Average intake is only 1.5% of body weight in the first 2 weeks for light- weight feeder calves. Anything that can be done to enhance intake after arrival reduces the length of time in which the immune system is compromised by short- term nutrient deficiencies. WHAT IS OPTIMAL IMMUNITY? The optimum immune response is the one that is the shortest in duration and the lowest in intensity while successfully eliminating the pathogen. Reducing chal- lenges to the immune system by providing a clean environment and reducing stress can improve growth rate, even in the absence of disease. In normal healthy cattle, there is a trade-off between growth and immuni- ty – both cannot be maximized at the same time. This is not usually a practical concern because the immune system functions very well at nutrient levels ideal for growth. Compared to the adapted feedlot steer, the stressed feeder calf is in a unique situation because of the conflicting nutrient demands for immune activation (vaccination and/or disease exposure), responding to stress, recove­ ring from short-term nutrient deficiencies, and growth. This animal has potential to respond to some key immune enhancing nutrients with significantly increased gain and improved immunity. Om die produktiwiteit van produksiestelsels vir beeste te verbeter. Adviesdiens vir herkouervoeding Voerprosessering, voedingsbestuur en formulering van voere vir volhoubare produksieprestasie Formuleer en verskaf konsentrate om formulasies te komplimenteer Dr. Kobus Swart 083 262 0946 • [email protected] 22 SENWES SCENARIO | TECHNOLOGY & INNOVATION 2018