Vet FAS - Grade: A++ PDF

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Range of essays for the module FAS....

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Vet FAS Semester two 2014/15 You are called to a dairy farm in order to trim the feet of 5 cows. While you are there, the farmer indicates that he is seeing a lot of lame cows lately and you decide to carry out a herd investigation. Describe how you would: a. Assess the prevalence of lameness in the herd. b. How you would determine if the problem was due to infectious or non-infectious causes of foot lameness c. Describe two common preventative strategies for the control and prevention of infectious foot lameness.

a. The first step in establishing the prevalence of lameness in the herd is to individually score each cow in the herd. Ideally this should be done before or after milking so each cow can be scored clearly and individually over a short distance. Lameness scoring ranges from one to five and is characterised by signs such as an arched back, favouring a limb, short strides, head-bobbing and leaving one limb non weight bearing. It is important to detect subclinical lameness as well as clinical lameness. Cows with a locomotion score of one stands and walks normally with all feet placed with purpose. Their back posture standing and walking is flat. Cows with a locomotion score of two are mildly lame. They are subclinical or subacute cases of lameness and although they’re not technically lame ideally they should be trimmed. The cow will walk with a flat back and arches it when they walk, the gait is slightly abnormal. Cows with a lameness score of three are considered clinically lame but only mild to moderately, and the lameness is rarely picked up. A cow that’s moderately lame stands and walk with an arched back, short strides involving one or more legs. Locomotion score four cows are clinically lame, their backs are arched while standing and walking, favouring one or more limbs but still can bear weight on them. Cows with a lameness score of five are severely lame and are very easy to pick up. Their back is arched, they refuse to bear weight on one limb and refuse to or have great difficulty moving from a lying position. Generally 90% of all the lameness is in the foot, 80% of that is in the hind limb and 80% of those cases are in the outer or lateral claw. Cows that score three or higher are considered lame and should be treated according to their individual diagnosis. The prevalence on Irish dairy farms is usually ~ 25-55%. Target prevalence on farm should be less than 10%, with 90% of cows having a locomotion score of two or less.

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b. The best method of detecting whether the causes of lameness is infectious or non-infectious is to diagnose the type of lameness in cows scoring three and above on the locomotion score. This will involving lifting the legs of the lame cows to examine their feet. Cows that are lame due to infectious lameness such as foot rot, interdigital necrobacillosis and digital dermatitis will present with visible signs of bacterial infection such as swelling, pain and discharge or smell and a similar infection will be common amongst most cows in the herd due to the spread of the infection. Non-infectious lameness causes include laminitis, white line disease, foot abscesses, solar ulcers, and solar haemorrhage and under run sole. In these cases, growth of the hoof will not be uniform and loss of normal weight bearing function will be obvious. The cow’s environment should also be inspected as it can give an idea of whether lameness is infectious or non-infectious. If the environment is poorly designed e.g. the cattle are walking long distances to be milked these can predispose to non-infectious lameness; similarly if the underfoot conditions are poor or the cattle are standing in slurry this may indicate the lameness is of the infectious type. c. There are many ways of preventing infectious causes of lameness. Firstly, regular footbath is effective against the spread. A solution of 5% CuSO4 or 5% formalin or an antibiotic such as lincomycin or oxytetracycline can be diluted in water and put in a foot bath for the cattle to walk through. Cows should be allowed to stand in a clean, concreted area following he footbath to allow their feet to dry. A second method of preventing infectious lameness is to monitor environmental hygiene. For roadway, housing and yards they should be scraped down or power washed and disinfected with a strong disinfectant. Roadways should have a stable surface, possibly concrete or gravel, as walking in muddy conditions can contribute to the spread of lameness. Cubicles should be scraped down and treated with a small amount of lime; tanks in slatted sheds should not be overflowing where cattle are standing in slurry.

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Describe the changes in energy requirements in single, twin and triplet-bearing lowland crossbred ewes during the last 8 weeks of pregnancy, and explain how these may be met in a typical mid-season lambing flock. Generally around the time of scanning, the farmer should separate his ewes into groups depending on the number of lambs the ewes are scanned for, in order to adjust the feeding for each group. In the last six to eight weeks of pregnancy ewes must be steamed up. Around 8 weeks before birth, lambs weight 15% of their birth weight and weigh about 0.6kg. By week 4, they weight 50% of their birth weight and weigh about 2.1kg each. By week 2, they weight 75% of their birth weight and weigh about 3.2kg. Lambs are generally born at about 4.3kg, depending on the sex of the lamb and the litter size. As 85% of foetal growth occurs in the final 8 weeks, nutrition in this time is very important to ensure both the ewe and her lambs are in good condition. Generally, twin bearing ewes gain 1.0kg per week, whereas single bearing ewes generally gain 0.5kg per week. TH nutrition of single bearing ewes especially should be monitored as overfeeding and underfeeding can lead to increased risk of dystocia and increased mortality. Lambs born at 2kg birth weight generally have a 10% survival rate and lambs above 4.0-4.5kg are at a high risk of dystocia. In the final 8 weeks of gestation, many farmers steam up i.e. increase ewe’s daily feed intake. This ensures strong healthy lambs and prevents twin lamb disease. It’s important that ewes maintain their body condition as lactation and the lamb’s average daily gain in gestation may cause loss of body reserves. The ewe’s intake requirements generally increase from 0.898 UFLs in week 6 prior to lambing to 1.45 UFLs one week before lambing. In weeks 1-3 of lactation, intake requirements increase again to 1.85 UFLs. This can be challenging as roughage intake in ewes decline sin late pregnancy due to decreased space in the abdomen due to the increasing pregnant uterus. When deciding daily rations for different groups of ewes, it’s important to remember that daily rations for ewes depend on bodyweight and BCS, litter size, roughage quality and stage relative to lambing. Ewes should be scanned for litter size as single bearing ewes need to be fed less and can be fed on good hay alone, until around 3-4 weeks pre-lambing when they need to fed concentrates. Concentrate feeding should peak at 0.4kg per ewe per day during the week of lambing for single bearing ewes. Triplet bearing ewes need to be fed more. They should start on concentrates around 8 weeks before lambing and this should increase to a peak of 1kg per ewe per day during week of lambing. If silage quality is poor, more concentrates will need to be fed. If ewes are in poor BCS i.e. BCS 2, they will need more concentrates. Twin bearing ewes should start off at 0.2kg of concentrates depending on silage quality at around week 7 and this should increase to a peak of 0.7kg during week of lambing. If ewes aren’t scanned they should be all fed as if they were twin bearing and body condition should be monitored. When feeding silage to pregnant lowland ewes, the DMD of the silage should be tested. Ideally ewes should be fed 70% DMD hay or silage. Although ewes have a preference for hay and will have a good DMI, it’s rare to get 70% DMD hay so good quality silage should be fed instead. Singles require 1.22 ULs and twins require 1.37 UFLs two weeks prior to lambing and if medium quality silage only provides them with 0.785 UFLs per day, they will be in energy deficit going into lactation which can cause weaker lambs being born, higher lamb mortality, lower milk supply, poorer maternal bonding, lower milk supply, lower lamb growth rate and a higher incidence of prolapse. Because of this it’s important to feed good quality silage as well as supplementing with concentrates so ewes meet their daily UFL requirements. SF

You are asked to attend a marine Atlantic salmon fish farm to investigate an increase in mortality. When you arrive at the edge of the net-pen, the farmer tells you the fish are off their feed and you can see the fish are lethargic and hanging around near the water surface. a. Describe what steps you would take from here to investigate what is occurring, including observations you would make and what diagnostic tests / samples might be helpful. b. Finally name two important infectious diseases that can affect Atlantic salmon during the seawater phase. a.

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