Outbreaks of Scour in Cattle & Sheep
Phil Rogers MRCVS
Grange Research Centre, Dunsany, Co. Meath, Ireland
CAUSES: Parasitism, infection, intoxication or toxicity and allergy are the main causes of herd/flock problems of scour. Severe mineral imbalances may be associated with lowered immunity and scour, but they are not as important nationally as the other causes.
AT PASTURE: The main causes are:
|Parasitism||gastrointestinal, liver fluke|
|Infection||Viral (BVD/Mucosal Disease, etc); Bacterial (E. coli, Salmonella, others) protozoal (Coccidia, Cryptosporidia, others)|
|Intoxication and toxicity||enterotoxaemia; lush grass scours (high-N, high-K herbage, NPN, nitrate); plant and fungal toxins; insect toxins (beetles, ladybirds); chemical toxins; excess mineral supplements (especially excess Mg); algal toxins (especially stagnant or contaminated water)|
|Allergy||plant, chemical or contact allergens|
ON SILAGE: The main causes are as above but other common causes are:
|As above||See causes of scour at pasture, above|
|Poor quality silage||pH >4.5, ammonia-N >15% of total-N|
|Fungal toxins||mouldy feed or silage|
|Acidosis||excessive or uneven intake of concentrate or molasses etc|
|Antibiotic contamination of concentrate||especially lincomycin contamination|
SCOUR IN YOUNG CALVES can arise in:
|Compromised immune system||High quality
colostrum (2-3 l in the first 6 hours of life, and 4-5 l in the
next 24 hours) is essential for immunoglobulin transfer to the
Foetal infections (Leptospirosis, BVD etc) and deficiency of trace elements & Vitamin E in late pregnancy can compromise the immune system of the neonate. This may increase susceptibility to scour, pneumonia, navel-ill, joint-ill etc.
In neonatal calf scour, if lab tests confirm deficiency in dry cows, supplementation of the affected group of neonates with the relevant trace elements and vitamins can quickly verify the clinical significance of the deficiency. Alternatively, drench the affected group of neonates with the relevant mineral(s). See drench formula, enclosed.
If minerals are involved, a definite response should occur quickly. If a response is obtained, ensure that all dams in late pregnancy get a good Dry-Cow mineral for at least 1 month pre-calving in future. Ensure that the young calves get a good mineral supplement also.
|Poor dam nutrition||Faulty dam nutrition can cause poor quality colostrum, or secretion of milk that clots poorly in the calf's abomasum. Failure of milk to clot increases speed of passage through the gastrointestinal tract.|
|Neonatal infection||Pathogens (E. coli, rotavirus, coccidia, cryptosporidia), etc can cause severe scour, especially in bought-in, stressed, or immunocompromised calves.|
|Poor calf nutrition||Inadequate feeding or quality of colostrum is a primary cause of low immunity in calves. Poor preparation or feeding of milk-replacer, or feeding too much carbohydrates can cause indigestion / nutritional scour.|
|Poor calf management||Poor hygiene, ventilation, and housing increase the incidence of scour in calves and lambs. Young animals should be kept comfortable and well fed.|
SEVERE MINERAL IMBALANCES can cause scour at pasture or indoors by:
Identify and correct the causal factors, including control of parasitism, infection, intoxication/toxicity, allergy and severe mineral imbalances.
Mineral supplements: If the levels of Cu, Co, Se, I, Zn are low on blood test, it is advisable to increase the supply of those elements. If minerals are only marginally deficient in blood, further supplementation with those minerals is unlikely to eliminate scour.
A quick way to check if mineral deficiency is involved is to give a good mineral supplement high in trace elements. If scour continues for more than 1 week afterwards, the cause is unlikely to be due to mineral deficiency.
A TRACE ELEMENT DRENCH FOR COWS, CATTLE AND CALVES: As an alternative to feeding trace elements in mineral mixes, the following may be used in small herds, preferably dosed at 1-2 week intervals:
Weight to mix (g)
sodium selenite (30.0% Se)
Include copper sulphate ONLY on specific veterinary advice. Add distilled water to 30 litres. Shake until ingredients are fully dissolved. In practice, depending on the specific deficiencies identified on the farm, only 1-3 of the ingredients are used together. The unwanted ingredients are omitted from the formulation.
|LABEL THE DRENCH
DOSE: CLINICAL CASES OR CALVES OF DEFICIENT DAMS: 17 ml/100 kg LW once/week.
THE USE OF PERIODIC DRENCHES OF TRACE ELEMENTS
SHAKE CONTAINER WELL between every few doses. Many drenches, especially those combining anthelmintics and trace elements, are not solutions: they are colloidal suspensions. If the container is not shaken frequently during use, de-mixing of the colloidal suspension can cause sedimentation of trace elements. The upper layer of the suspension may contain low concentrations of trace elements and the lower layer may contain toxic levels. Animals dosed from the upper layer may get too little supplement. Those drenched from the lower layer can die of acute poisoning within 1-3 days of drenching.
DRENCHING TECHNIQUE: Drenching can be dangerous. Consider other methods of supplementation before drenching. Inhalation of part of the drench can kill stock, cause shock, or lung damage. Drench carefully at the correct dose. Avoid damage to the back of the throat. Avoid drenching too fast.
COPPER POISONING (see Web article): If they inhale part of the drench, or if the dose is too high, cattle can die after Cu drenches. N.B. Unweaned calves are easily poisoned with copper; they absorb Cu more efficiently than weaned calves and adult cattle. Unweaned calves should not get Cu in drenches unless Cu deficiency has been confirmed by a veterinary surgeon by a herd blood test and/or on clinical/postmortem findings. If they need a Cu supplement, dosing with oral Cu oxide (CuO) capsules or Cu-containing glass boluses is safer than drenching Cu compounds. Unweaned calves could get one 4-8 g CuO bolus in a gelatin capsule at 2-4 weeks of age(2).
SELENIUM POISONING (see Web article): Under EU Feed Regulations, total Se intake by cattle should not exceed 0.57 mg Se/kg total feed DM.
Endemic Se poisoning occurs in a few localised areas in Ireland, due to toxic Se levels in soil and herbage. Do not use high-Se supplements within 5 miles of known Se-toxic areas without veterinary confirmation of Se deficiency in the herd.
(2)A dose of 8 g CuO/100 kg LW/year usually is recommended in adults. Two doses/year at 4 g/100 kg LW each time gives longer protection than 8 g/100 kg LW given at one time. Especially on high-Mo farms, severely Cu-deficient herds may need 16-20 g CuO/100 kg LW/year but 4-5 doses/year at 4 g/100 kg LW each time gives longer protection than the whole dose given at one time.
Note: CuO capsules can be used safely during the breeding season, but Cu injection is not advisable at that time.