Outbreaks of Scour in Cattle & Sheep

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:
Cause

Parasitism

Infection


Intoxication and toxicity



Allergy
Comments

gastrointestinal, liver fluke

Viral (BVD/Mucosal Disease, etc); Bacterial (E. coli, Salmonella, others) protozoal (Coccidia, Cryptosporidia, others)

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)

plant, chemical or contact allergens
ON SILAGE: The main causes are as above but other common causes are:
Cause

As above

Poor quality silage

Fungal toxins

Acidosis

Antibiotic contamination of concentrate
Comments

See causes of scour at pasture, above

pH >4.5, ammonia-N >15% of total-N

mouldy feed or silage

excessive or uneven intake of concentrate or molasses etc

especially lincomycin contamination
SCOUR IN YOUNG CALVES can arise in:
Cause

Compromised immune system

















Poor dam nutrition



Neonatal infection



Poor calf nutrition




Poor calf management
Comments

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 calf.

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.

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.

Pathogens (E. coli, rotavirus, coccidia, cryptosporidia), etc can cause severe scour, especially in bought-in, stressed, or immunocompromised calves.

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 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:
  • primary or secondary effects on the gut (excess K, Mg, S, Mo; deficient Cu, Co);
  • reducing immunity to infection (deficient Cu, Co, Se, I, Zn);
  • reducing immunity to parasitism (deficient Cu, Co, Se).
REMEDIAL ACTIONS

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:
Compound


sodium selenite (30.0% Se)
cobalt sulphate (21.0% Co)
potassium iodide (76.4% I )
+ copper sulphate (25.4% Cu)
Weight to mix (g)
(see Label below)

35.0
100.0
137.4
(only on vet advice) 2480.3
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 as follows:
  • POISON. FOR ANIMAL TREATMENT ONLY. KEEP AWAY FROM CHILDREN. USE ONLY IN CATTLE AND ONLY AS DIRECTED. SHAKE THE DRENCH WELL BEFORE DISPENSING AND BETWEEN EVERY FEW DOSES. (SEE WARNINGS BELOW).

DOSE: CLINICAL CASES OR CALVES OF DEFICIENT DAMS: 17 ml/100 kg LW once/week.
  • PREVENTATIVE: 17 ml/100 kg LW/week or 33 ml/100 kg LW/2 weeks. Dose every 1-2 weeks for best results in herds at risk of Co and I deficiency. Dosing at intervals of >3 weeks may not control those deficiencies fully. Do not exceed the stated dose.

WARNINGS ON THE USE OF PERIODIC DRENCHES OF TRACE ELEMENTS
The label or accompanying leaflet on the drench should contain the following warnings:
  • POISON: Use ONLY on the advice of your VET.

    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.
Phil Rogers MRCVS, Lucan, Dublin, Ireland​
THE NYCAVMA IS HONORED TO HOST & MANAGE THE PHIL ROGERS ARCHIVE