CP1 Wk6: Calf Scour

CP1 Wk6: Calf Scour

1. 25% of pre-weaned calves affected by scour

   • 20% mortality
     • Farmer doesn't notice early signs
     • dehydration, acidosis
   • Survivors have 2ndry damage to gut: intesinal villi shortening, poor intestinal absorption, poor growth rate.
     • Financial implications

2. Aetiology: nutritional, infectious, stress

   • Stress from mixing of age groups, dirty & wet housing, etc
   • Poor mixing of milk replacer, poor quality of milk replacer, not feeding at correct temperature
     • Feed at 42 degrees
     • Too much milk replacer CANNOT cause scour
   • Bacterial: E.coli, Salmonella & Clostridium Parasitic: Crypto & Coccidia Viral: BVD, Rotavirus & Coronavirus
     • E.coli: Affects very young calves, 1-3 days old, picked up from calving pens. F5 adhesion antigen and enterotoxin cause Cl- secretion into the gut lumen, where water follows. Also causes villi damage.
     • Salmonella: neonatal or older, has different presentations. Picked up from carrier animals. One of the only situations in which WOULD use antibiotics in treating calf scour
       • Hypersecretory diarrhoea
         • Increase in fluid content of the lumen so the gut's absorptive capacity is overwhelmed
     • Rota & Coronavirus: picked up from calving pen, everywhere in environment
     • Clostridia: bacterium has alpha and beta toxins, calf can die very quickly without any clinical signs
     • Crypto: Oocysts excreted in the faeces are immediately infective: faecal-oral route of infection
     • Coccidia: oocysts need time to sporulate in the environment so are not immediately infectious
       • Affected calves are weeks- months old

3. 2 types of diarrhoea

   • Malabsorptive
     • BCCC
       • BVD (crypts), crypto (villi), clostridia (mucosal necrosis) & corona (villi)
     • Rate of cell loss > cell replacement
       • Reduction in surface area of the small intestine for enzyme digestion & absorption of water & nutrients
         • Malabsorptive, osmotic diarrhoea
   • Hypersecretory
     • E.coli & salmonella
     • Overwhelms absorptive capacity of the large intestines- increased fluid content of faeces
   • Rota causes both forms

4. D- lactate acidosis

   • Due to S.I. damage, undigested carbs enter the L.I., which doesn't normally happen
     • Carbs in the L.I. begin to ferment and acidify, where acidification favours the growth of lactic acid producing gram +ve bacteria (Lactobacilli)
       • Lactate is then absorbed into the calves body & has direct toxic effects on the brain
         • Clinical signs: wide base stance, absent palpebral reflex & ataxia
   • Seen in calves with S.I. diarrhoea and rumenal milk drinkers- e.g. head down in bucket

5. Clinical signs of straight dehydration

   • Skint tent, enophthalmos & reduced suckle reflex