Testing colostrum quality
Colostrum quality can not be determined by appearance. Colour and consistency only indicate the fat components of the colostrum, and a measure of the IgG either in the colostrum or in the blood of the neonate is required to determine the immunological quality.
Storage: Colostrum can be stored, however this must be done correctly to prevent reduction in immunological status and to prevent outbreaks of disease. Disease outbreaks may occur from feeding colostrum as it is a very good medium for bacterial growth. The best way to store colostrum is to freeze it immediately after milking in a small, clean, secure container. It can be frozen for a year with minimal reduction in quality. It should be thawed thoroughly before giving it the the neonate by leaving it at room temperature, or by gently warming it in water (no hotter than 38 C). Thawing colostrum at high temperatures or by using a microwave can irreversibly denature the immunoglobulin (proteins) and thus reduce the colostrum's immunological status. Colostrum can be refrigerated for approximately 5-7 days. However, this must be done immediately after milking, and it must be discarded after this period to prevent colostrum with bacterial overgrowth being fed to the neonates.
Pasteurisation: If diseases such as Mycoplasma, Johnes and Bovine Leukaemia Virus are present on the farm it is important not to feed affected colostrum to the new born calves. To prevent the spread of these diseases, long time pasteurisation of the colostrum at low temperatures can be performed. However this causes a 40% reduction of antibody content.
1. Radial immunodiffusion
This is the gold standard test for measuring IgG levels in the calf blood. However, it is expensive and not readily available. It would be a more appropriate test in the individually affected calf.
2. Serum total protein
This is a simple, rapid and inexpensive test that may be performed on farm as part of a calf health investigation. However, with a sensitivity and specificity of approximately 80%, it is most appropriately used as a herd level test. It is recommended that a minimum of 12 samples are taken to allow interpretation on the herd level. It is important that the calves sampled are clinically healthy as dehydration can elevate the total protein levels increasing the proportion of false negatives results.
After blood sampling into a plain tube, the blood can be left to clot at room temperature and then by way of transferring the serum with a pipette or syringe, the total protein can be measured using a refractometer. Alternatively a centrifuge may be used. Using a cut off of 55 g/l, 4/12 or greater is sufficient to say failure of passive transfer is problem on the farm. If the result is 2-3/12, then sampling of further calves is recommended. On smaller herds where 12 calves may not be available at one time, samples should be taken as appropriately aged calves become available until 12 are sampled.
- It can be used as an on farm assessment of antibody levels in calves.
- A blood sample is taken when the calf is 2-8 days old.
- The total serum protein is measured using a refractometer.
| Total serum protein (mg/dl) | Amount of colostrum absorption |
|---|---|
| <4.5 | None |
| 4.5-4.9 | Inadequate |
| 5.0-5.2 | Poor |
| 5.3-5.4 | Borderline |
| 5.5-7.0 | Acceptable |
3. Zinc sulphate turbidity test (ZST)
This has similar properties to the measurement of serum total proteins regarding interpretation. However, samples usually need to be sent to a laboratory to be analyzed and there is concern that haemolysis can affect the accuracy. The cut off usually used is 20 units.
- An easy, quick test to determine the immunological status (amount of immunoglobulins)/adequacy of passive transfer in foals and calves.
Calves
| Amount of serum immunoglobulin (ZST UNITS) | Outcome | Cause of death/outcome |
|---|---|---|
| <10 | Death | E.Coli infection; effects of diarrhoea and pnemonia |
| 10-30 | Less likely to die | Recurring diarrhoea that can lead to death and/or pneumonia |
| >30 | Healthy | May have slight diarrhoea and/or pneumonia |
Foals
If the foal has not nursed effectively from the mare 2-3 hours post partum then at least 1L of good quality colostrum must be given. The quality can be determined using a colostrometer. Specific gravity >1.060 is roughly equal to a colostrum IgG concentration of >3000 mg/dl. The immunological status is especially important in foals to prevent infection. IgG levels in foals peak at 18 hours post parturition.
Ideally check ZST at 12-18 hours or earlier if:
- Suspicion of FPT (eg. inadequate suckling etc).
- If colostrum is available.
Check ZST at 48 hours if:
- Foal is clinically normal.
- Financial constraints (can only afford to do the test once).
- No colostrum available to use at 12-18 hours anyway, so if there is a problem a plasma transfer would have to be performed to provide adequate antibodies.
| Amount of serum immunoglobulin (mg/dl) | Age of foal | Action needed |
|---|---|---|
| <200 | <18 hours old | IV plasma infusion |
| 200-400 | <18 hours old | Antibiotics treatment at first sign of infection and IV plasma infusion |
| >400 | <24 hours | Oral colostrum |
800 mg/dl is considered normal and these foals are at less risk of infection compared to foals with failure of passive transfer.
4. Lateral-flow immunoassays
These are relatively inexpensive calf side tests that are available in some countries. Manufacturers report a high sensitivity and specificity. The test reports a positive/negative result as opposed to a specific level and therefore gives less information than other tests.
Colostrometer
- Used to determine the immunological status (quantity of immunoglobulin especially IgG ) of the colostrum.
- It should be used before giving any foal or calf colostrum.
- Measures the specific gravity of the colostrum which correlates to the IgG concentration.
- The colostrum must be at room temperature (20°C). Below this the colostrometer will overestimate the amount of IgG present, and if it is above, the amount of IgG will be underestimated.
| Colostrometer colour | Colostrum quality | Quantity of immunoglobulin (mg) | Suitability for use |
|---|---|---|---|
| Green | Good | 50-140 or more | Give to neonates for the first 24 hours or for longer if in abundance |
| Yellow | Fair | 20-50 | Only use in the first 24 hours if no 'green' colostrum is available |
| Red | Poor | <20 | Only use after 24 hours for 2-3 days |
| Colostrum Quality Testing Learning Resources | |
|---|---|
 Full text articles available from CAB Abstract (CABI log in required) |
Nutritional and immunological importance of colostrum for the new born. Prajakta Kuralkar; Kuralkar, S. V.; Veterinary World, Rajkot, India, Veterinary World, 2010, 3, 1, pp 46-47, 11 ref. - Full Text Article |
References
Books
A.H. Andrews Bovine Medicine - Diseases and Husbandry of Cattle Blackwell Publishing 2004 2nd Edition
Koterba, Drummound and Kosch Equine Clinical Neonatology Williams and Wilkins 1990
P. Lydyard, A. Whelan and M.W. Fanger Immunology Garland Science 2nd Edition 2004
Websites
www.sheepandgoat.com
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