BVSc V Semester Test 9 June 2003

Transcription

1 BVSc V Semester Test 9 June Define summer ventilation. (3) Defineer somer ventilasie. (3) The type and amount of ventilation required to remove excess heat produced in the house to keep the house temperature at the required optimum temperature for the type and age of bird. 2. You are a farm manager on a large commercial broiler farm with cross- ventilated, climate controlled houses. It is the middle of summer and you expect the temperature at 2pm to reach 35 degrees Celsius outside. Your chickens are due to be slaughtered in 5 days time. a) About how old are your chickens today? (1) b) List the steps you would you take to ensure that the chickens in your care do not overheat today. (10) a) 32-37days b) increase air flow with fans 2 use cooling pads or mist sprayers 2 lift feeders during hot part of the day 2 add water soluble vitamins and minerals to drinking water 2 cool drinking water 1 walk chickens slowly to move hot air 1 (increase fat content of diet to reduce heat generation) (decrease stocking density) 3. Sketch a naturally ventilated broiler house, showing the key features in the house design. Please write short notes to describe the features you have drawn and to explain why they are important. (6) 1. Orientation long axis east/west to avoid direct sunlight on birds 2. Roof cheap materials, insulation vs radiation, fairly high, nok on roof to allow convection cooling 3. Sides wire mesh, bird proof, low solid walls to allow ventilation but avoid draft on birds 4. Curtains movable, open from top allow vent. Avoid draft. 5. End walls solid, man-door and truck door 6. Floor - concrete, slight drainage slope for cleaning 4. What negative effects does an increase in stocking density have on broilers? In view of these disadvantages, why do farmers still tend to overstock their chicken houses? (4+2) Decreased growth Worse FCR Higher condemnations at slaughter Increased general stress and disease problems Increased meat yield per square meter 1

2 Capital outlay determined by size of structure 5. Discuss the role of photoperiod in the management of commercial laying hens in the following facets of the life of the laying hen: a) The first week of life. (2) b) During rearing (2) c) Inducing the onset of lay, including a brief summary of the hormonal pathways underlying the onset of lay. (6) 0-7 days : 23 hours light to find feed, 1 hour darkness to avoid panic. Rearing 1-16 weeks : 8-10 hours, never increase hours during rearing. Early lay : weeks, increase by ½ hour per week to maximum of hours, never decrease during lay. Late lay : maintain hours to cull at about weeks. Used together with body weight to stimulate onset of lay. Increasing daylight length (artificial or natural) reduces secretion of melatonin by the pineal gland which stimulates release of FSH and LH by the pituitary gland, leading to onset of oestrus 6. Describe different types of feeders (including temporary feeders) used for broilers and explain their correct use. (7) 1. paper or plastic sheeting first few days, 20-30% of brooding area. 2. feed trays 1/100, first few days 3. chain feeders 5cm/bird,not common 4. tube feeders 1/50, manually filled, lip level with birds back 5. pan feeders 1/50, automatic with auger, lip level back of bird general comment feeders too high -> cant eat feeders too low -> feed wastage Beskryf die verskillende soorte voerders (insluitend tydelike voerders) wat vir braaikuikens gebruik word en verduidelik hoe hulle reg gebruik moet word. (7) 7. You are the manager of a medium sized commercial caged layer farm ( hens). a) If you were to buy point of lay pullets, what age would the hens be on arrival on your farm? (1) b) What viral vaccinations would you give the birds while in lay and which application routes could you use to apply them? (6) c) The owner of the farm has had some cash flow problems recently and has decided not to sell off the older flocks of birds, but to keep them in production. They are now reaching their 80 th week of age. What problems would you expect to experience with these older flocks in terms of egg production, egg quality, egg size? At what point would you have to strongly advise the owner to sell the flock? Is there any economically viable alternative to selling the flock at this stage? (6) a) weeks b) live ND, live IB by fine spray, drinking water c) egg production decreases, poor shell quality, large eggs when value of eggs sold is less than cost of feed for flock 2

3 birds can be moulted 8. What behaviour in young chicks will indicate that they are too cold? (2) Huddle together, cheep loudly) 9. With reference to broiler breeder management, please answer the following questions. a) At what age is de-beaking usually done? (1) b) How is the growth rate of the birds controlled during rearing? (2) c) What biosecurity measures should be applied on broiler breeder rearing sites? (3) d) Why is separate sex feeding applied when broiler breeders are in production? (3) a) 7-21 days b) feed restriction based on weekly weighing c) strict access control (fencing), showers at entrance, change into clothes used only on site d) different nutrient requirements, principally calcium due to female egg production, females are aggressive feeders 10. Name 3 effects of prolonged storage of eggs on the incubation of eggs. (3) Lys 3 effekte van uitgerekte stoor van eiers op die uitbroei van die eiers. (3 Reduced hatchability, increased incubation time, contaminated eggs and omphalitis 11. List five viruses that are vertically transmitted through the egg in chickens. Maak n lys van vyf (5) viruse wat vertikaal oorgedra word deur die eier van hoenders.. EDS, leucosis group, AE, CAV, Reo 12. Name the virus causing each of the following diseases. Gee die naam van die virusse wat die volgende siektes veroorsaak. a. Infectious laryngiotracheitis b. Chicken infectious anemia. c. Infectious bronchitis d. Infectious bursal disease e. Fowl pox (5) a. herpesvirus b. circovirus c. coronavirus d. birnavirus e. pox virus 13. List the most likely post mortem findings in broilers infected with a mild case of Infectious Bursal Disease. (3) 3

4 Swollen bursa, gelatinous - > shrunken bursa 14. What is the most important effect of such a disease outbreak in broilers? What economic consequences may this have for the farmer and why? (3) Immunosuppression Increased susceptibility to 2 disease and increased mortality 15. Why are broiler breeders frequently vaccinated at about 16 weeks with an inactivated IBD vaccine? Evaluate the advantages and disadvantages of this strategy. (6) To hyperimmunize parents to pass on high levels of maternal immunity to progeny -> high and uniform titres in progeny, protective up to about 3 weeks ->high titres interfere with live vaccine application, difficult to predict when to vaccinate progeny -> not vaccinating - > high CV in immunity but can give early live vaccination. 16. Layer chicks, in their first week of life, are submitted to your practice with the complaint that about 30% of the flock has developed nervous symptoms shortly after hatching. Twenty chicks are submitted to you alive for post mortem examination. Most of the chicks submitted exhibit non-specific nervous signs such as incoordination, paralysis and tremors. They show no other symptoms. The macroscopic post mortem examination is negative. a) Which viral infection is the most likely cause of the problem? (1) b) What further tests/examinations could you do to confirm your diagnosis? (3) c) Explain how this disease problem probably arose in this group of chicks. (3) d) What treatment would you recommend in the affected birds? (1) e) How would you control the disease in the future? (4) a) Avian encephalomyelitis picornavirus b) Histopathology encephalomyelitis Brain material of affected chicks injected into clean chicks, look for Sx Paired ELISA serology c) Parent flock became infected with virus while in lay. Resulted in vertical transmission of the disease to progeny. d) None - cull e) Live virus vaccination of parent flocks between 8 and 16 weeks Elisa at 17 weeks to confirm successful vaccination. Can still revaccinate if poor response. 17. Newcastle Disease. a. Name the aetiological agent. (1) b. Name the 3 organ systems affected by Newcastle disease. (3) c. Describe the clinical picture in a flock of unvaccinated broilers affected by velogenic Newcastle disease. (4) d. Give the full name of a test used to differentiate the pathogenicity of different types of Newcastle disease virus. (1) 4

5 e. Describe a typical vaccination programme against Newcastle disease in broilers. (4) a) Paramyxovirus b) GIT, respiratory, nervous c) >75% mortality, nervous signs, green diarrhoea, respiratory signs incl haem tracheitis. d) MDT or ICPI (in full) e) Live vaccines at day old, boost between 10 and 21 days, second booster Inactivated vaccines late rearing twice usually 18. Avian influenza a. Name the aetiological agent. (1) b. What are the most important signs/post mortem lesions would you expect to see in laying hens in the event of an outbreak of highly pathogenic avian influenza in South Africa? How would these differ from an outbreak of Newcastle disease in laying hens? (3) a) orthomyxovirus b) acute high mortality (up to 100%) not ND as hens vaccinated generalized petechial haemorrhages in carcasses nervous signs 19. Which viral diseases are associated with egg shell changes in layers? (3) Watter viruses veroorsaak veranderings in die eierdop in lehenne? IB, ND, EDS, AI 20. Marek s disease. a) What lesions would you see at post mortem examination in the event of an outbreak of classic Marek s disease? (2) b) Why is the cutaneous form of Marek s disease, often associated with broilers, very seldom seen in South Africa? (2) c) A small scale breeder of show poultry brings chickens to you which prove to have Marek s disease. What advice would you give him about control of the disease and why? (4) a) unilateral enlargement of sciatic or brachial nerves b) do not recycle litter, slaughter early c) difficult because vaccine must be given at day old, vaccine available only in 1000 doses, Rispens needs to be stored in liquid nitrogen but not too serious generally, only erosive 5