[SOUND] [MUSIC] So we're standing here in the treatment room of the food animal hospital at the College of Veterinary Medicine at University of Illinois. If you see behind me this is our medicines cabinet and in this medicine cabinet there's a whole range of therapeutics that we give animals. We use drugs to control pain. We use them to treat parasites, but a number of these drugs are actually antibiotics. And when you see, we have ten or 15 antibiotics that we can use in food animals. And why do we need antibiotics? Wouldn't it better for our food if we didn't give any drugs at all? Well the fact is that when we need medicines, there's often indication of when the animal isn't coping with the infectious disease process. The pathogens that we've mentioned in other parts of the course, the bacterial particularly, when they overcome the immune system. That's when the animals need help in combatting that infection. Now we don't have really many good drugs against viruses, we have good drugs against parasites, against nematodes, and worms that inhabit intestinal tract and the skin. But we don't have good drugs against viruses, so most of our antibiotics are effective against certain bacteria. Now, we talked about the immune system. The immune system is a wonderful part of the body, and we've talked about it being a part of homeostasis. Its main function is not to fight infection so much, but to restore normality, but there are certain times in animal's life when the immune system doesn't work as we wanted to and that's when an infection becomes established. Now sometimes it's the infectious pathogen itself that determines whether disease becomes evident in an animal. So the pathogen is present in an amount which exceeds the immune system. Or the strength of the pathogen, certain virulence factors, allows it to bypass the immune system. But we want to consider today the times at which the host immune system isn't working as well as it could be. There are certain stages of the animal's life and certain things that we do managementally that impact immunity. And if we can do those things well, if we can redesign our management system so that immunity is optimized. Then what it can do is reduce the need for medication. Reduce the amount of antibiotics that we need. Now it's probably never going to be at the stage where we never use any antimicrobials at all. So drugs are an important part of our armamentarium as producers and as vets. But we can reduce their use certainly. So what stages of the animal's life and what do we do managementally that impacts deleteriously the immune system? So the first stage of life in which the immune system is most likely to be impaired is in a newborn. We see a lot of infectious diseases in our newborn animals, whatever the species, so it is a period of susceptibility. And why is that? Well if you think about it, the newborn, whether they are from within the egg or within the uterus, they have not been exposed ideally to any bacteria at all, any microbes at all. So they essentially have a naive, an untrained immune system. Having not been exposed, the immune system is not been up regulated. Now a lot of species, particularly our more precocious ones are more active ones such as calves and lambs and piglets, particularly calves and lambs. Their immune system is fully functional at birth. It just hasn't been exposed. It doesn't have memory and is not regulated. So, they depend almost entirely on the first milk that they receive from their mothers. So by taking in that colostrum and then the intestine absorbing them, or engulfing those proteins and taking them into the body. They become part of the newborn's immune system. So any managemental factor that impairs that colostral intake is going to lead to a situation of immune deficiency. If that newborn doesn't get the antibodies, doesn't get the cytokines, doesn't get the cells, then essentially it doesn't have a fully functional immune system. So a bacteria pathogen can come it, and it really has an immunologically susceptible, an immunologically naive animal, and it's very easy for them to contract infections. So what can we do managementally? Well, making sure that the colostrum is of a certain quality, making sure that the animal gets the colostrum early on. Making sure that the colostrum is clean, and making sure that the right amount of colostrum is given. All of those are important management factors that make sure that immune deficiency doesn't occur in the newborn. For additional stages in which the animal becomes immunologically susceptible are those times in which there are transitions in life, physiological transitions. The big ones we think about in our growing animals are weaning. So when the animal is taken from a milk based diet to solid diet, that's a huge change for the intestinal tract to now be coping with a different nutrient. Very often too, at weaning, there are different management practices that take place. For instance, a young calf might have been by itself and now it gets introduced into groups. A piglet of litters might have been on their mom and then suddenly they're separated from their mother and now put into different groups of animals. So not only the process of weaning itself, the physiological effects of that as far as nutrition, can impair the immune system. We know that the immune system takes a huge amount of energy and protein from the diet. So that nutritional maintenance is really important during those transition periods, such as at weaning. But also there's other factors which lead to stress within the animal. You'll hear in other parts of the course when we talk about how stress impedes the immune system, particularly through the HPA, or hypothalamic pituitary adrenal axis, and through the secretion of hormones such as cortisol and catecholamines, which impede or impair certain parts of the immune system. So those transition periods, from a dietary standpoint or from a managemental standpoint are really important and can represent times when the immune system is impaired. That also happens in adults. For instance, when an animal is mixed with animals that it's not familiar with. That's a stressful time for that particular animal. You might have animals that are being sold, so an animal going to market mixed with other animals there. That mixing and the interactions, those new social interactions can also, through those stress mechanisms, can impede immunity. Probably as you know yourself, the weather also has a huge impact on immunity. There are animals that live in wet environments and dry environments. And animals that live in cold environments and live in warm environments. And each of them independently have good immune systems. The problem often occurs when the weather changes and weather changes drastically, and the animal then has to adapt to that temperature change or that humidity change. Some of the changes can be transmitted to the animal systemically so that change in energy needs is it has to adapt to lower temperatures. But they can also impact the immune system, not just systemically, but also locally. When there is a change of cold weather, that can affect the mucosal immune system, the immune system in the lining of the respiratory tract, or the lining of the intestinal tract as well. So all of those factors, weather is a huge element impacting the immune system of our animals. So how can we minimize the impacts that weather has on their immune systems? It's really predicting or anticipating when changes in weather are going to take place. By controlling the environment, by making sure that those changes, even though they're outside the animal, don't impact the animal too much. Good bedding, good nutrition, good housing, protection against drafts, all of those things can keep the animal comfortable and protect its immune system from being impacted negatively. It's also important to understand when major physiological transitions occur in the animal, that's a time in which the immune system can be impaired. Think about pregnancy. Pregnancy is a remarkable, physiological process. As soon as the animal becomes pregnant and the fetus starts to grow, essentially there is a foreign animal inside of this host. The genetics of the fetus, 50% usually, they're 50% of the genetics, the genes are incompatible with the genes of the host. So, the immune system should theoretically respond to that. But pregnancy has a whole set of endocrinological pathways and local physiological changes which make sure that the fetus is protected against the immune system of the dam. So pregnancy in some way changes the immune system. And we could say almost impedes the immune system. Similarly with birth, birth is by definition a stressful event. There's a lot of physical activity. There's again a whole set of endochronological changes, and for the dam that can be an immune suppresitive event. If all goes well, by managing pregnancy, by managing births, so that it's kept within healthy barriers, then that's a way in which managementally we can make sure that the immune system of pregnant animals and birthing animals is optimized. We see a large amount of infectious disease after transport or associated with transport. And again transport itself can be non-stressful. As long as it's done well and managed appropriately. There might be some element of training of your animals so that they're used to livestock trailers or to being moved. But when transport is managed in such a way that it's a stressful event for the animals, so when there's a huge amount of mixing of unfamiliar animals, when there's over crowding, when the environment of the trailer or the noise of the trailer are not managed appropriately. That can be an event which again through those same neuroendocrinological pathways appropriately stress impedes the host immune system. And then very often the process of transport, so let's say an animal is transported for many hours. If they're not fed well or watered well during that transport, if the trailer is not set up to manage cold or temperature changes, all of those can impede the immune system of the animal. So when we 're looking at livestock diseases, looking at how we transport animals and how we optimize that process is really important in controlling infectious disease because it enhances the immune ability. The ability of that animal to resist the infections to which it will be exposed. We've talked about the impact of nutrition and how important good nutrition is for full immunity. Another time in which we see immune deficiency is when we have sub optimal nutrition. That might be on certain pastures which are missing certain elements, certain trace minerals such as copper. Copper deficiency can lead to an increased susceptibility of the immune system to disease because copper is part of the enzyme pathways, part of the super oxide pathways as well that take place, and a part of the immune mechanisms of some of the cellular components of the immune system. So how do we help that? By maximizing our good nutrition. That's going to help the animal's immune system in combating infections. So the last element we want to consider when we're thinking about immune deficiencies or impediments to the immune system, is the impact of disease itself. So, immune deficiencies cause disease, but disease causes immune deficiencies. So, viruses themselves can interface with the immune system in such a way that they make the host more susceptible to bacterial pathogens. That what happens in respiratory disease. The viruses come in first and damage some of the protective mechanisms of therefore, allowing bacteria to become established. So disease itself can be an impediment to the immune system. That's why prevention of disease is actually immunologically beneficial. If we can prevent subclinical disease or disease that we can't see very often, we can actually make our animals more resistant to the disease that we can see. So you can see that there are a number of factors that affect and interface with the immune system. And the immune system is difficult because we don't actually see it, and it's hard to measure. It's hard to look at an animal and say that animal is immunologically impaired. So, what we have to do is no wait for signs of immunological impairment, that's too late. We want to make sure that all of our management practices are put in place in such a way that it maximizes the ability of the animal to defend itself against pathogens. And one of the biggest things to incorporate into our management systems is consistency. As you have seen from a lot of those things we've talked about, it's changes, it's change that impacts the immune system. So, if you establish a management practice, and you're consistent in that, then very often the immune system of the animal will be the best it can be. [MUSIC]
