Colostrum - Assessment of and Sources for Foals

Colostrum varies in quality (amount of IgG and type of specific antibodies) in mares. It is prudent to assess the quality of colostrum in mares at birth and have alternate sources readily available for newborn foals. Determining IgG of colostrum must be done pre- suckle and immediately postpartum. This indirectly identifies those foals which could be at high risk for failure of passive transfer. Assessment allows determination of high quality colostrum which aids adequate passive transfer immunoglobulin and/or saving some colostrum for freezing (colostrum banking).

Assessing IgG Content

Subjective Criteria

• Thick, sticky consistency similar to liquid paraffin. Creamy yellow color.
• Specific gravity of colostrum is correlated with IgG concentration. (See below)
• Visual assessment not adequate to determine quality (IgG content).

Labaratory Assessment of Colostrum

• Immunoglobulin (IgG) content (Immunology Laboratory, single radial immuno-diffusion).
• Anti-erythrocyte alloantibodies that may result in neonatal isoerythrolysis can be rapidly detected by the jaundiced foal agglutination test (JFA) (see Chapter 35 - Neonatal Isoerythrolysis).
• Other commercial tests for IgG are available.

Method to Assess Colostrum^1-3

Colostrometer

• This technique affords immediate results "on the farm" by determination of the specific gravity of a 5 ml aliquot of colostrum obtained immediately post foaling. i.e. pre-suckle.⁴
• Colostral specific gravity should be > 1.060 and contain at least 3000 mg IgG/dl
• Product name and Manufacturer: Equine Colostrometer J-281, (Jorgensen Laboratories – Loveland, Co, USA). www.jorvet.com

Sugar Refractometer

• Proven reliable for colostrum IgG- BRIX % reading
  • Place 1 drop of colostrum on refractometer
  • If reading is 10-15 poor IgG concentration, 15-20 borderline, 20-30% have 60g/dl of IgG in colostrum–adequate-
• Manufacturers:
  • Atago Sugar Refractometer, Atago Inc., Japan. www.atago.net/usa
  • Bellingham and Stanley, Ltd. Turnbridge Wells, Kent, UK. http://www.bellinghamandstanley.com

Program for Minimizing Failure of Passive Transfer

(Using gms of IgG) Foals fed an estimated 1.5 gm of colostral IgG/kg of body weight had reasonable levels of serum IgG at 12 hrs of life.⁵

• Mares produced 2.3 liters ±500 ml of colostrum.⁵
• Foals with less than 400 mg/dl IgG at 12 hr (or foals that can’t nurse) should receive 1.00-1.25 gm colostral IgG/kg of body weight. This is fed starting at 2 hr of age in volumes of 200 ml per feeding.⁵

(Using volumes of colostrum) If colostral IgG is normal or high, then feed foal 1-1.5 liters of colostrum starting at 1-2 hrs of age using 8 oz per feeding at 2 hr intervals. Check IgG at 12 hrs.

• If colostral specific gravity is 1.050 - 1.060 - supplement foal with 10-12 ounces of good quality colostrum via nasogastric tube.
• If colostral specific gravity is (very poor) < 1.050 - administer 24 ounces (approximately 1 liter) of good quality colostrum (sp.gravity > 1.060).

Only pre-suckle colostrum test results can be evaluated reliably. Evaluating colostral quality after a foal has nursed 1-4 hours is of little value because the normal rate of decline in colostral quality is unknown.

Alternate Sources of Colostrum

Bovine colostrum has been shown to be absorbed and provides some short duration of passive transfer to foals.^6,7

• It may not provide the specific antibodies needed for protection against all equine pathogens.
• Administer 2-4 liters (400 ml q 2 hr starting by 2 hrs of age)
• Use only when you don’t have access to other forms of artificial or mare colostrum. Treat foal with antibiotics as well.
• RebornTM is 100% pure natural bovine colostrum replacement This can be used as a replacement or in addition to the mare ́s colostrum. Bovine colostrum followed by equine plasma has been linked to anaphylaxis in some foals.

Commercial concentrated serum products for oral use. www. lakeimmunogenics.com. These are derived from equine serum - for IV and some given orally are absorbed to some extent if administered in first 12 hrs of life.

Risk factors for Mares with Low Colostral Specific Gravity (IgG in Milk)⁵

• Mares greater than 15 years of age have lower milk IgG.
• Mares producing foals early in the year.
• Breed: Standardbred mares have lower milk IgG.
• Weather: mares giving birth on nice sunny days had more IgG in milk.