Cattle production Part 3: Growing cattle Introduction... 2 Ethics and animal welfare... 3 Ethics right or wrong?...3 Animal welfare...5 Disease... 7 Pathogens...8 Nutrition...20 Legal Responsibility...21 Summary... 22 Suggested answers... 23 Exercises Part 3... 30 Part 3: Growing cattle 1
Introduction Introduction People who are responsible for the care of animals have both ethical and legal obligations towards those animals. People must be aware of the welfare needs of animals in their care so these needs can be addressed. In this part you will examine the obligations to, and welfare of animals. One of the important ways that farm managers can maintain the welfare of animals is to prevent and treat diseases. In order to do this effectively they must have a good understanding of the disease and the control options available to them. In this part you will practice using a system that organises information about a disease so it is easier to develop control measures. You will also look at the use of chemicals as a control measure, and how the problem of resistance can arise. This part contributes towards an understanding of Outcome H2.2 from the Agriculture Stage 6 HSC Course. The syllabus can be found on the Board of Studies, NSW website at http://www.boardofstudies.nsw.edu.au 2 Cattle production
Ethics and animal welfare Ethics and animal welfare Ethics right or wrong? Ethics is concerned with making decisions about what is right or wrong. Most of the time it is clear whether a particular course of action is ethical or unethical. We can refer to our past experiences and community values to help us decide. Sometimes situations arise where it is unclear whether a course is ethical or unethical. These situations often concern decisions about new technology, and the arguments that arise are usually between groups that have very different views on the ethics of the technology. It is up to the public to keep informed so they can understand the issues involved, and can make their own decisions on where they stand ethically. The ethics in any situation are a very personal choice, we draw on our own experiences and culture to make decisions. Ethics are not static, over time we can change our ideas of right and wrong when new discoveries are made and community attitudes change. In agriculture, ethics is mostly concerned with how animals are treated. It is generally agreed that animals have certain rights, and people should try to ensure that these rights are met. Often there is conflict between the rights of animals and the needs of people. An example of this conflict is the killing of animals to provide meat for people to Figure 3.1: Media such as television, radio, magazines and newspapers is often used by representatives of opposing groups to air their views. Part 3: Growing cattle 3
eat. Some individuals respond to this by making an ethical choice to become vegetarian. For other people it is sufficient to know that there are government regulations regarding the humane slaughter of animals. Some people may feel that intensive housing of animals is unethical. A response to this might be a decision not to purchase products produced in this way, for example by buying free range eggs instead of battery farmed. Animal experimentation is an area that continues to cause ethical conflict. The ethical attitudes of the general community towards animal experiments have been canvassed, and used by the Australian government to produce regulations that aim to minimise the suffering of experimental animals. There are also legal requirements that research institutions must have ethics committees to decide if planned animal research projects are ethical or not. Ethical debates regarding agricultural plants are generally about the application of new technology, and the impact on consumers and/or the environment. Genetic modification and plant breeder s rights are two areas that have caused controversy in recent times. To make an ethical decision means balancing alternatives. The best way to do this is to evaluate the factors that are involved on each side of the argument, the benefits and risks, and use them to reach a decision. If you are interested in exploring the issue of ethics there is a lot of literature available. Try the St James ethics centre at http://www.ethics.org.au/ or the Australian and New Zealand Council for the Care of Animals In Research And Teaching at http://www.adelaide.edu.au/anzccart/. Can you think of any current ethical debates in the community? Think about what has been discussed lately in the media. The introduction of technologies such as transgenics, cloning and stem cell research have all caused ethical debate when their implications are explored. Issues surrounding the control of serious exotic diseases such as Newcastle disease, foot and mouth disease, mad cow disease and anthrax can often cause ethical dilemmas. Animal management techniques can sometimes be an issue such as caged layer hens and the mulesing operation in sheep. Complete Exercise 3.1 - discuss a current ethical dilemma in agriculture. 4 Cattle production
Animal welfare Animal welfare is of great importance to people managing and working in cattle production enterprises. Cattle that are not content are not as healthy, and will not grow well and produce marketable products. This will affect the profits of the enterprise. There is also concern in the general community that animals are kept in appropriate conditions. This can even impact on the marketing of the product. As you discovered in the preliminary course, there are guidelines that restrict the ways that animals can be kept and treated to ensure that their basic welfare needs are met. Think about what you consider to be the welfare needs of cattle. Write in the space below some important headings that you think could be used in a booklet on cattle welfare. Look at a copy of the Australian Model Code of Practice for the Welfare of Animals, report 39 Cattle. It can be found on the internet at http://www.publish.csiro.au/pid/4831.htm, or can be purchased from CSIRO publications. Skim through the document noting the major headings and points. How well do your headings match up? Are there any aspects of cattle welfare that you had not considered? Use the code of practice as a resource to help you decide if the following situations have welfare implications, and to make appropriate recommendations on any action to be taken. 1 Lotfed cattle in a windy situation where dust and feed are blowing into their eyes and noses. Part 3: Growing cattle 5
2 Cows routinely locked away from access to drinking water for part of the day. _ 3 Using sticks to move cattle through yards. _ 4 Castration of five month old calves without anaesthetic. _ 5 A mixed herd of polled and horned cattle. _ 6 Calves weaned at five weeks of age. _ 7 Transporting sick calves. _ 8 Underdosing cattle with drench. _ Check your answers. 6 Cattle production
Disease Disease A disease is an upset in the normal functioning of an animal that has an adverse effect. This upset causes the animal to show symptoms which can include: death or weakened condition lowered production change from normal body temperature loss of appetite, loss of weight or failure to grow in young animals abnormal discharges, for example mucus, blood changes to condition of skin, for example rash infertility or abortion abnormal behaviour, for example moving away from other animals, lying down, bellowing, aggression. The set of symptoms shown by an animal can help establish the cause of the disease. Diseases can be caused by a number of different factors, including: pathogens, for example viruses, bacteria, fungi, protozoa, insects, arachnids, nematodes and helminths genetic disorders, for example dwarfism in cattle (this aspect will be looked at in the next part) plants, for example lantana toxicity poor nutrition, for example deficiency of vitamin D causes rickets. In this part you will be looking mainly at diseases caused by pathogens. Part 3: Growing cattle 7
Pathogens Pathogens are micro-organisms or invertebrates that cause disease. In order to cause disease most pathogens must gain entry to the body of an animal via: wounds made by the bites of insects or other animals, or by physical injury from fences or sticks that can allow microorganisms, such as tetanus, to enter the animal the mucous membranes of the respiratory tract pathogens are discharged by infected animals into the air by coughing, sneezing or just breathing out, and can travel from host to host by water droplets or carried along in the wind, infectious pneumonia is spread in this way consuming contaminated food or water leptospirosis, a bacterial disease of cattle and sheep, can result from drinking contaminated water, a common problem on farms is the contamination of pastures with nematodes and helminths, which then infest sheep, cattle and goats direct contact at joining time, for example vibriosis is a sexually transmitted disease of cattle other organisms that assist the transmission of a disease. These carriers are called vectors, and are most commonly insects. When the vector bites the animal it transmits the disease causing organism into the animal and then the animal may contract the disease. The protozoa that causes tick fever in cattle is transmitted by Boophilus microplus, the cattle tick. This means that control of tick fever depends on control of the cattle tick. Akabane is a virus disease carried by sandflies. When the sandflies bite pregnant cows they transmit the disease, resulting in abortion or birth of brain damaged calves. Figure 3.2: The cattle tick (an arachnid) is a vector of disease. It carries a protozoan which causes tick fever in cattle. 8 Cattle production
In the recent past the usual single strategy for the control of any disease was to use strong chemicals. As more is understood about the development of pathogen resistance to chemicals, and the effects of chemicals on the wider environment, this strategy has been shown to be ineffective. Resistance In any population there is variation. If you look around at a group of people you will see differences that make each person recognisable as an individual. As well as the differences you can see, there are also hidden differences. For example, some people may be more disease resistant than others. Figure 3.3: The differences in the external appearance of individual people can be clearly seen. A lot of the variation in a population is due to slight genetic differences. These differences can be passed on from one generation to the next (which is why people in a family tend to look alike). Many of these variations have no real advantage or disadvantage for the individual, so they just continue to appear in the population. Consider a population of pathogens. Although it may not be apparent to us, they also have slight genetic variations between individuals. If pathogens are exposed to a particular chemical, it is likely that among a large population there will be some individuals that have a variation that gives natural resistance to the chemical. These individuals will survive the use of the chemical when others die. The resistant pathogens that remain will breed with each other. Some of their offspring will inherit Part 3: Growing cattle 9
resistance, so there will be more resistant pathogens in the population. Sometimes the combined effect of two resistant parents can produce an even stronger level of resistance in the offspring. With continued use of the chemical there is selection pressure for the whole population to become resistant to the chemical. Eventually the chemical becomes ineffective against the pathogen. Development of resistance is particularly a problem in organisms that have a short time from one generation to the next, for example bacteria, as resistant populations can develop very quickly. If a chemical is used on a population of pathogens in addition to one or more alternative control measures it becomes less likely that resistant individuals will survive to reproduce, and this means more effective control. Draw a series of diagrams to illustrate how chemical use can result in a resistant population of pathogens. Check your answer. It is now accepted that a variety of measures used together is a better method of disease control than using a single chemical. The strategic use of a number of measures, including non-chemical methods, is known as integrated pest management or IPM. For IPM to be effective all aspects of the disease need to be considered. 10 Cattle production
Disease triangle Disease occurs when there is an interaction between an animal, a pathogen and an environment that favours the disease. This interaction of key factors can be summarised by what is called the disease triangle. host pathogen environment Figure 3.4: The disease triangle. For disease to occur there needs to be: a susceptible host. A susceptible host animal is not immune to the disease. Young, injured or diseased animals are more susceptible a source of the pathogen. For example, spores in the soil or larvae on the pasture. Sometimes pathogens are brought onto a property by new stock. a favourable environment for growth of the pathogen. The conditions depend on the particular pathogen, for example, warm and wet weather, dusty conditions, lush pasture. IPM program The disease triangle is the key to developing an effective IPM program. You can: manage the host so it is less susceptible. For example - vaccinate the animal or control other diseases so it is not in a weakened condition. exclude, weaken or kill the pathogen. For example - excluding the pathogen from the property by quarantine measures, killing the pathogen by administering medication. Part 3: Growing cattle 11
make the environment less favourable for the pathogen's growth and multiplication. For example - if the pathogen requires moist conditions keep the pasture short to allow it to dry out. If the pathogen needs dry dusty conditions use a sprinkler system to dampen down the dust. Cattle diseases In cattle production systems it is important to control disease so productivity is maintained. Cattle can be affected by a number of diseases. Pink eye commonly occurs in summer caused by an infection bought on by dust, flies, hot weather and seeds the eye waters, becomes inflamed and cloudy, then ulcerated Le ptospiros is infection causes abortions and can kill cattle leptospira is harboured in damp places eg marshes Ephemeral fever cattle get a fever, become stiff and lame caused by a virus, carried by mosquitoes Akabane produces abnormal calves at birth most are still born caused by a virus that is spread by a biting midge Scours causes include changes in diet, weeds, infections and deficiencies animals can become dehydrated and die quickly because they are unable to absorb nutrients and water Footrot caused by a germ that lives in the soil; wet conditions are needed germ enters the animal through injuries to the feet foot becomes red and swollen, animal becomes lame Worms many different species, distribution depends on climate eg summer rainfall favours the barbers pole worm eggs hatch on pasture in favourable weather conditions and are then eaten by animals significantly reduces the growth of animals Clostridial diseases various bacteria present in the soil cause diseases such as tetanus, black leg, pulpy kidney, malignant oedema and black disease may be present in soil, faeces and feed; can enter the animal through wounds can travel in the wind or running water Figure 3.5: Some diseases of cattle. 12 Cattle production
1 Identify the disease on the previous diagram that is actually a symptom. 2 Practice identifying the three points of the disease triangle. Use coloured pens or pencils to highlight references to host, pathogen and environment on the diagram: blue host red pathogen green environment. Check your answers. Tetanus Tetanus belongs to a group of diseases that are caused by related bacteria. They are often called Clostridial diseases. The pathogen is a bacterium, Clostridium tetani, which is commonly found in the soil. Clostridium tetani only causes tetanus when it is present in damaged body tissue. Puncture wounds provide a suitable environment for the bacteria's growth by healing on the surface and allowing the multiplication of the bacteria in the anaerobic conditions underneath. The host can be cattle, sheep, horses, goats, pigs or humans. Symptoms of tetanus occur from about four days to three weeks after infection is established in a wound. The toxin produced by the bacteria causes spasm or cramp in the animal's muscles. The animal walks stiffly, lockjaw develops and the third eyelid protrudes out across the eye. The head and neck are held out stiffly, with the tail slightly raised, legs are stiff and muscles rigid. Later the animal goes down with legs held out straight and stiff and head drawn back. Convulsions occur and the animal dies when breathing muscles become paralysed. Affected animals nearly always die. Figure 3.6: Diagram of a sheep with the symptoms of tetanus infection. Note the stiff legs and the turned back head. Part 3: Growing cattle 13
The symptoms for humans with tetanus are similar to those in animals. People who are working in agriculture can be particularly at risk. Tetanus bacteria can enter the body through deep puncture wounds and also a tiny pinprick, a scratch from an animal, splinters, insect bites and burns that break the skin. Most young children are routinely vaccinated, a booster is given at about 14 16 years of age, and then at least every 10 years to maintain immunity. An extra booster will sometimes be given by a doctor if a person has a wound that breaks the skin, particularly if it is dirty, and if the last booster was more than 5 years ago. Find out your own immune status for tetanus. When was your last tetanus vaccination? On most properties cattle are also routinely vaccinated to protect them against tetanus and other related diseases. Vaccination alters the susceptibility of the host, so even when the pathogen is present, and the environment is suitable the disease will not progress. Answer the following questions using information in the leaflet for Ultrabac 7 vaccine. You can download this free from the Pfizer Animal Health website at http://www.pfizeranimalhealth.com.au 1 Identify where this vaccine should be stored. _ 2 Identify the diseases that Ultrabac 7 vaccine can protect against. _ 3 Identify whether booster doses of this vaccine are recommended, and when they should be given. 4 The term aseptically means that sterile methods need to be used. Explain why sterilisation of syringes and needles is recommended. 5 Propose reasons why the recommended injection site for cattle is high on the side of the neck. _ 14 Cattle production
6 Look at Figure 2.1, the calendar of operations for Ondiong Murray Grey Stud, in the previous Part of this module. Evaluate the vaccination schedule they operate on the farm, compared to the schedule in the Ultrabac 7 vaccine leaflet. Check your answers. Pinkeye is another cattle disease caused by bacteria. You will need a copy of Primefact 336 Pinkeye in Cattle from the NSW Department of Primary Industries http://www.dpi.nsw.gov.au/ to help you complete Exercise 3.2. Worms Intestinal worms are a problem on Ondiong due to high stocking rates, warm temperatures and high rainfall. The main problem is from Ostertagia, a small brown stomach worm that lives in the intestines of affected animals. Pastures become infested with worm larvae, which are picked up by cattle when they are grazing. Stressed cattle are more susceptible, so care must be taken at weaning, during severe weather, and if cattle have restricted nutrition. Worms use resources that could be used by cattle for growth. Animals are weakened, and so are more susceptible to other diseases. Worms also cause scouring (diarrhoea) in calves. Cattle with a high worm burden are slower growing, lethargic and have dull coats. Severe infestations can cause death. At Ondiong the cattle are drenched to control worms. Calves are drenched every six weeks until weaning. Heifers are drenched at joining and calving. Bull calves are drenched at 12, 15 and 18 months of age. As cattle age they develop immunity to worms, so older cattle do not usually require drenching, although working sires are drenched annually if necessary. Where possible paddocks are rested from cattle for at least 4 months to allow time for most larvae to die. Part 3: Growing cattle 15
Figure 3.7: The life cycle of Ostertagia. The worm is most active in summer and late autumn. Eggs need warm and moist conditions to hatch. This worm favours areas with uniform or winter rainfall. (Scanned: McKenzie, T (Ed). Beef production guide. Cattle health and handling. (1991). NSW Agriculture.) 1 Identify the host, the ideal environment and the pathogen for this disease. 2 Suggest the elements of a worm control program for cattle that uses the concept of the disease triangle, and avoids the development of resistant worm populations. Refer to Part 4 of Looking at ewe for ideas. _ 16 Cattle production
3 Look at the leaflet for Valbazen drench. You can download this free from the Pfizer Animal Health website at http://www.pfizeranimalhealth.com.au. Assess the dosage of Valbazen drench you would need to drench a 200kg steer for roundworms. Check the answer section. New methods Australian researchers are continuing to work on the development of better ways to control worms. One area that looks promising is the use of resistant animals. Strains of sheep and cattle have been identified that have natural genetic resistance to parasites. Another new approach uses fungi to kill the hatching worms. Read the following article about this innovation. It has been taken from a newsletter called Turning the worm, produced by NSW Department of Primary Industries. Biological control of nematode parasites with fungi Dr Malcolm Knox CSIRO Livestock Industries, Armidale NSW 2350 Feeding fungus to livestock may be a future solution to controlling gastrointestinal parasitic round worms, according to a novel approach being developed by CSIRO Livestock Industries. Rather than trying to cure round worm infestations with drugs, the nematode destroying fungi break the worm life-cycle by preventing livestock ingesting infective larvae when grazing. This is achieved by feeding the fungal spores to livestock, which then pass intact through the gastrointestinal tract and are excreted with the worm eggs in the dung. The fungal spores then germinate and grow networks of traps that ensnare and kill the worm larvae soon after they emerge from the eggs. Major round worm parasites including barber s pole worm (Haemonchus spp.), black scour worm (Trichostrongylus spp.), small brown stomach worm (Ostertagia spp.) are potential targets for this type of treatment as are many other species of nematodes. Part 3: Growing cattle 17
Controlled trials have established that this fungus can reduce worm larvae numbers by more than 90% without any harmful effects on dung and pasture microfauna. Currently, CSIRO Livestock Industries and collaborators from industry and other research organizations are working with specialist providers to produce commercial quantities of spores of Duddingtonia flagrans an Australian isolate of a nematode destroying fungus first identified in a survey of sheep s dung in the early 1900 s. Some frequently asked questions related to this project are: Are there any harmful effects on soil organisms? Studies conducted so far have indicated that there are no detrimental effects of treatment on soil nematode populations or on insects and mites associated with the breakdown of faeces and pasture detritus. We have also observed that the fungus does not spread from the faecal pat and does not persist for long after the faeces has broken down. How will the fungus be applied? Application of the fungus will most likely be through some type of feed supplement or premix and possibly through a feed block. This approach may be of particular value for sheep and other livestock that are given nutritional supplements for part of the year. Will we need to apply the fungus all year round? No, it is more probable that the fungus will be used strategically for short periods of 2 4 months to ensure low numbers of worm larvae on pastures when stresses like weaning and lambing normally lead to increased susceptibility to infection. At these times, nutritional supplements are often beneficial in reducing the effects of parasitism and adding the fungus will increase the benefits by reducing larval availability. Will the fungus replace other methods of worm control? The fungus will most likely be an additional option for worm control rather than the final solution. Hopefully, some reduction in chemical useage will eventuate as programs for integrated worm control using combinations of chemotherapy, animal breeding, pasture management and biological control with the fungus are developed. 18 Cattle production
When will the fungus be available for use on farm? The first fungus products are expected to be commercially available after completion of large-scale trials in sheep. These trials are anticipated to commence later this year and will take approximately two years to complete. Turning the Worm Issue 10 April 2002 NSW Agriculture. 1 Using one organism to control another is called biological control. Identify the organism that is being tested to control parasitic worms. 2 It is important that the biological control organism does not become a problem itself. Identify areas tested by the CSIRO to ensure that the fungus is safe to use. 3 Outline how the fungus could be put in contact with worm larvae. 4 Evaluate the potential of the fungus in an IPM program. Check your answers. If you are interested in looking at more recent editions of the TTW newsletter then access the NSW DPI website at http://www.dpi.nsw.gov.au. You might also look at a website called WormBoss that provides worm updates at http://www.wormboss.com.au/ Part 3: Growing cattle 19
Nutrition Some cattle diseases associated with nutrition have already been mentioned in Part 2. Complete the following statements. is a condition where foam forms in the rumen that prevents the escape of gas. The rumen quickly swells up and the pressure that it exerts on vital organs such as the heart and lungs can cause death. is a condition where a sudden change to increased levels of grain in the diet of a ruminant produces large amounts of lactic acid. This causes an increase in acidity in the rumen and in severe cases may result in death. Check your answers. Disease can also occur if the level of nutrition is inadequate or if the diet is deficient in supplying particular nutrients. A calf disease that occurs in particular areas of Australia is called white muscle disease. This has been shown to be caused by a lack of the mineral selenium in the soil of these areas. The mineral deficiency of the soil means that pasture is deficient, and so the cattle are also deficient. The disease can be treated by either applying selenium to the soil in a fertiliser mix or by dosing the cattle directly with selenium. This is applied as a drench, as an injection, or as a pellet that remains in the rumen and slowly releases selenium Figure 3.8: Map of selenium deficient soils 20 Cattle production
Legal responsibility In Australia the legal responsibility for control of animal disease is divided between the different government levels. The Commonwealth government is responsible for quarantine and international animal health matters, including disease reporting, export certification and trade negotiation. It also pays for some national disease control programs. The State and Territory governments are responsible for disease control within their boundaries. Each state and territory is divided into regions under the control of a government veterinary officer, and these regions are subdivided into animal health districts administered by inspectors. Individual producers are responsible at a farm level for prevention and treatment of disease in the animals under their care. Producers should be aware of diseases that are common in their district, and they should develop plans to prevent or treat each problem. If treating animal disease with chemicals, the producer must be very careful in the use of these chemicals. On the labelling for veterinary chemicals a withholding period for the chemical must be stated. A withholding period is the time that must elapse between the treatment of an animal, and the slaughter of that animal or collection of its milk for human consumption. The producer is legally required to observe this period. 1 Identify the withholding period associated with the use of Valbazen using the Valbazen cattle drench leaflet. 2 Identify the withholding period for Closal drench from the Closal drench label at http://www.coopersanimalhealth.com.au 3 Predict the impact of a withholding period on the management of cattle. Check your answers. Part 3: Growing cattle 21
Summary Summary Ethics is concerned with making decisions about right and wrong. Ethical debates can arise when the ethics of a situation are unclear. Animal welfare needs should be met to ensure optimum production levels. There are government guidelines on minimum animal welfare requirements which must be met by the people with the responsibility of care for animals. A disease is an upset in the normal functioning of an animal. A disease will cause symptoms in an animal that can assist with identification of the disease. With continued use of a chemical, resistance can develop in a pathogen population. Integrated Pest Management (IPM) uses a variety of measures, including non-chemical approaches to combat disease. Interaction of the host animal, disease pathogen and the environment causes disease. This interaction can be summarised by a disease triangle. Research continues into new methods of disease control. Producers must be careful to read chemical labelling so they can observe legal requirements such as withholding periods. 22 Cattle production
Suggested answers Suggested answers Animal welfare 1 This situation may be harmful to the long term welfare of these cattle as the dust can cause breathing and eye problems. Sprinklers or misters can be use to settle the dust and the feed can be dampened. Avoiding processing of feed very finely might also help. (1.2, 1.3.5) 2 The welfare guidelines require that the cows should not be deprived of access to water for longer than 24 hours. Depriving them of access to water for a short time every day is acceptable. If the period is regular or lengthy then it might be sensible for the producer to supply a trough to the area. (1.1.2) 3 A stick can injure the animal and is not acceptable. The welfare guidelines recommend that cane, leather or plastic goads be used instead. (4.10) 4 The guidelines state that calves up to six months of age can be castrated with a knife, or burdizzo, without anaesthetic. The earlier castration occurs the better for the recovery of the animal. (5.4) 5 Cattle with horns are more aggressive and may injure polled cattle. It is better to separate them into two groups if practical, or to dehorn or tip in an acceptable manner. (4.15, 5.8) 6 Calves that are weaned too early will not have a properly developed digestive system and will not be able to manage a non-milk diet. The guidelines require that calves are not weaned before 3 months for calves on their mother and 6 weeks for artificially fed calves. (5.10.5) 7 The guidelines require that sick calves should not be transported. The sick calves should be treated for their illness or destroyed if treatment is not possible. (5.11.7, 6.3) Part 3: Growing cattle 23
8 The drench will be ineffective if underdosed, resulting in a worm burden and possibly promoting resistance in the worm population. Overdosing can also be dangerous to the health of the animal. All chemicals should be given by carefully following the manufacturer s directions. Generally the dosage for a drench is calculated by the bodyweight of the animal, so inaccuracies can be reduced by weighing the cattle or by using a weight tape for a good estimate. (6.2) Resistance Check that your diagram series includes: a population with a variety of natural variations application of the chemical death of all individuals in the population without the protective variation breeding of surviving individuals a population with a large number of individuals that have the protective variation. Your diagram might look like this: application next generation of chemical population with variations resistant individuals survive many resistant individuals Cattle diseases 1 Scours (diarrhoea) can be a symptom of several different diseases. 2 Every point of the triangle is not mentioned for every disease. Blue the host The cow Footrot: germ enters the animal through injuries to the foot. The injury makes the cow susceptible. Clostridial diseases: can enter the animal through wounds. The wound makes the cow susceptible. 24 Cattle production
Red the pathogen Worms, barbers pole worm Leptospirosis, leptospira Ephemeral fever, virus Akabane, virus Footrot, germ (this is actually a bacteria) Clostridial diseases, bacteria present in the soil, faeces and feed. Can travel in the wind or running water. Green the environment Worms hatch on pasture in favourable weather conditions Leptospirosis harboured in damp places eg marshes Pinkeye commonly occurs in summer, brought on by dust, flies, hot weather and seeds. Footrot wet conditions are needed. Tetanus 1 This vaccine is best stored in the fridge. 2 Ultrabac 7 vaccine protects from blackleg, malignant edema, black disease, gas-gangrene, enterotoxaemia, tetanus and. 3 Additional doses of this vaccine are recommended. The second dose should be given four weeks after the first and the booster given 12 months later. 4 It is recommended that syringes and needles be sterilised before use to reduce the chance of the cattle getting tetanus and other infections from the injection. 5 The recommended injection site is easy to access when the animal is in a crush or race. If localised swelling occurs, the animal will still be able to function normally and there is no carcase damage to the more valuable muscle areas. 6 The Ondiong Murray Grey calves are vaccinated in August and September when they are four weeks old and again four weeks later. Cows are vaccinated annually in March. Yearlings are vaccinated in July. The vaccination program on Ondiong is very similar to that recommended for Ultrabac 7 vaccine. Part 3: Growing cattle 25
Worms 1 Host cattle Pathogen Ostertagia sp. worms. Environment warm, moist conditions 2 Host: Keeping cattle healthy and well fed will make them less susceptible. Extra care needs to be taken when weaning to put calves on clean nutritious pasture. Pathogen: Routine use of a drench could increase the development of a resistant population of worms, so testing for worm egg counts is important. Drenching can then be used strategically. The manager can spell paddocks for 4 months to let infective larvae die. Grazing with older resistant cattle or sheep will also reduce numbers of larvae. Environment: The worms are at their most vulnerable when they are infective larvae on the pasture. Dry weather at this time can cause their death. This effect is increased if pasture is kept short. 3 The steer would need to be dosed at a rate of 3 ml per 45 kg of bodyweight, which is approximately 13.5 ml, or 15 ml from the table. New methods 1 The organism is a fungus called Duddingtonia flagrans. 2 Studies have been conducted to test soil nematodes, and insects and mites associated with breakdown of manure, with no harmful effects detected. 3 It is suggested that cattle will eat the fungal spores mixed into a feed supplement. The fungus spores will be fed to cattle so that they leave the body in manure with the worm eggs. When the worm larvae emerge the fungi will also germinate. 4 The strategic use of the fungus to reduce numbers of worm larvae would fit in well with an IPM program that included the use of drenches, and pasture management strategies such as rotation and spelling. Worms with resistance to the drench are more likely to be killed, slowing the development of resistance in the worm population. The application of the fungus in a feed supplement will also help host animals resist infection. 26 Cattle production
Nutrition Bloat is a condition where foam forms in the rumen that prevents the escape of gas. The rumen quickly swells up and the pressure that it exerts on vital organs such as the heart and lungs can cause death. Lactic acidosis is a condition where a sudden change to increased levels of grain in the diet of a ruminant produces large amounts of lactic acid. This causes an increase in acidity in the rumen and in severe cases may result in death. Legal Responsibility 1 The leaflet states that there is a 10 day withholding period associated with this chemical, so the producer must wait 10 days before selling treated cattle for slaughter. The chemical is not be used for animals that are producing milk. 2 The leaflet states that there is a 28 day withholding period associated with this chemical, so the producer must wait 28 days before selling treated cattle for slaughter. 3 If animals are treated with chemicals that have a withholding period then the manager must have the ability to keep accurate records. These records must be able to identify individuals that have been treated, and flag them (or their products) as unsuitable for sale during that time period. If the withholding period includes products such as milk, the manager must have a system for disposal of milk from the affected animal, so that the bulk milk is not contaminated. Part 3: Growing cattle 27
Exercises Part 3 Exercises Part 3 Exercises 3.1 to 3.2 Name: Exercise 3.1 Discuss a current ethical dilemma in agriculture. Hints: The word discuss is one of the key words used in the Board of Studies syllabuses and examinations. It has a particular meaning when used in HSC exam questions. Discuss identify issues and provide points for and / or against BOS NSW 1999 The New Higher School Certificate Assessment support Document First identify a dilemma that has ethical considerations. There are some ideas in this part, or you can use the media to help you choose another. Watch the television news, listen to the radio news, look in newspapers and check news items on the internet. Sometimes internet news items will have links to sites that contain additional background information. Consider the different viewpoints that are associated with the dilemma. Try to identify different groups that have an interest. Work out the major arguments of the different groups and present these as points for or against. Sometimes group representatives will be interviewed in the media, and you can note down their major points. For other groups you may need to do some research to find out about the group and what it stands for. 28 Cattle production
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Exercise 3.2 Use Primefact 336 Pinkeye in cattle to complete this exercise. You may also use other information sources. 1 Outline the major symptoms associated with cattle affected by pinkeye. _ 2 Construct a disease triangle for pinkeye. 3 Propose an IPM approach for pinkeye based on your disease triangle. _ 30 Cattle production
4 Analyse the legal, ethical, and welfare issues associated with the management of pinkeye in cattle. Part 3: Growing cattle 31