NUTRITION ▶▶▶ Feeding for performance
The ability of a cow to remain healthy depends on many factors, not least its immune system. Competent immune function is critical to dairy cow performance and welfare – and nutrition plays a vital role in maintaining a strong immune system.
BY DR HELEN WARREN, EUROPEAN TECHNICAL MANAGER FOR RUMINANTS, ALLTECH T
he immune system is a biological defence mecha- nism made up of various tissues, cells and chemicals that aim to prevent disease and ill health caused by infections. The key is for the immune system to be
able to recognise the difference between disease-causing or- ganisms and normal cow tissues. The first part of the immune system is a physical one, in the form of skin. Cuts or abrasions to the skin can allow entry of pathogens into the body that subsequently stimulate the next step in the defence process – the innate, or non-specific, re- sponse, which causes inflammation. Following the initial, in- flammatory phase, a second, more specific, process occurs. An- tibodies are produced as part of this response; this is the basis of vaccination. This system also possesses ‘memory’ whereby memory cells from a previous infection remain in circulation. If the same pathogen is encountered for a second time, the re- sponse is more rapid and stronger. The failure of any stage of defence leaves the animal at higher risk of infection and/or disease.
Feeding and immune function Numerous factors influence immune function, including ge- netics, hormones, oxidative stress and nutrition. However,
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42 ▶DAIRY GLOBAL | Volume 7, No. 3, 2020
one of the most influential factors regarding immune func- tion is nutrition, and research demonstrates the adverse ef- fect of malnutrition on immune function in mammals. The transition period poses the greatest risk to immune func- tion due to the large amount of physiological stress on the cow. During the close-up period, cows can experience sup- pressed immune function (Sordillo et al., 2009). Both defi- ciencies in and excesses of various nutrients can result in im- paired immune function, so careful attention must be paid to transition cow diets. Minimising the negative energy balance (NEB) post-calving is an important goal for any nutritional plan. Animals with an NEB tend to have elevated levels of compounds associated with an increase in inflammatory conditions (Sodillio et al., 2009). Mobilisation of body fat to provide additional energy has detrimental effects on metabolism, as well as on the im- mune system (Ingvartsen and Moyes, 2012). Minimising NEB requires a healthy and efficient rumen, which can be encouraged by feeding a balanced ration using good-quality ingredients. As the calf grows in size, dry matter intake (DMI) decreases, meaning adjustments are required in nutrient density of the ration. Fat is often used to increase en- ergy density, but it must not be at the expense of ration bal- ance. Adequate dietary-soluble carbohydrates, as well as avoidance of excess dietary protein, should be taken into ac- count when formulating rations for these animals. That said, the cow should still be provided with optimal levels of forage to minimise the risk of digestive disturbances. Feed additives, such as live yeast, have been shown to improve rumen func- tion (Desnoyers et al., 2009). Dietary inclusion of live yeast, such as Yea-Sacc®
(Alltech Inc.),
can rapidly promote an anaerobic environment, helping de- sirable, fibre-digesting microbes to proliferate and efficiently colonise feed particles, resulting in lower rumen lactate con- centrations and a higher overall pH. Yea-Sacc is a proprietary strain of the live yeast Saccharomyces cerevisiae, with just this specific rumen activity, and its benefits are supported by a plethora of controlled animal performance data (Table 1). It works by metabolising excess oxygen entering the rumen, present via feed particles, thus helping to maintain an anaer- obic rumen environment. There is also stimulation of lactate-utilising bacteria, which helps to reduce the acid load in the rumen and avoid
PHOTO: BERT JANSEN
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