You should routinely assess the quality of each colostrum sample you collect.
Testing individual cows only takes five seconds using a Brix refractometer.
It is difficult to judge IgG content of colostrum visually.
A Brix refractometer uses a beam of light to determine the optical density of the colostrum.
The greater the protein level in the sample, the more light is bent from the light path. Values are read as a percentage.
Mix the colostrum sample well before taking a single drop for testing. Results are accurate and repeatable.
A digital Brix refractometer does not need a bright light source to read the scale, and takes the guess work out of the reading by supplying an exact number.
A Brix score (or density) of 22 per cent is the cut off for detecting good quality colostrum (IgG above 50 mg/ml).
If the colostrum sample has a value below 20 per cent it is of poor quality (less than 30 mg/ml). Do not feed it to calves during the first 24 hours of life, save it for feeding to calves at days two and three of age.
Newborn calves should be given the freshest, highest quality colostrum.
Older calves can be given older and lesser quality colostrum.
Work quickly
Time is of the essence in the transfer of immunity to the newborn calf.
The clock starts ticking as soon as the calf is born because the calf’s intestine can only absorb antibodies (IgG) for a short time.
Straight after birth the calf’s intestine absorbs the large IgG molecules easily.
Within six hours of birth the intestine’s ability to absorb IgG has decreased by 30 to 50 per cent.
Between 24 to 36 hours after birth no more IgG can be absorbed.
Calves should be removed from the calving area as soon as possible after birth to reduce exposure to pathogens that cause diseases like calf scours and Johne’s disease.
Leaving the calf to suck colostrum from the dam is no guarantee of successful transfer of immunity.
Continuing to feed colostrum to calves beyond the initial 24 hours (after the calf gut ‘closes’) may also have advantages, as the IgG can still bind to pathogens in the gut and help protect the calf from infections.
Colostrum is also a highly nutritious food for calves. Poorer quality colostrum should be reserved for feeding calves over 24 hours of age.
Quality and quantity
The quantity of colostrum each calf needs to achieve successful passive transfer depends on:
● The amount of antibodies (IgG) contained in the colostrum.
● The time elapsed after the birth of the calf.
● The cleanliness of the colostrum.
● Any special needs of the calf.
Testing quality with the refractometer takes the guess work out of how much to feed:
● Good quality (> =22 per cent Brix): give two 2 litre feeds within the first 12 hours of life.
● Poor quality (< = 22 per cent Brix) or if not tested: give two 3 litre feeds within the first 12 hours.
● An additional feed of 2 litres of good quality, fresh colostrum in the next 12 hours is beneficial.
Greater volumes and more frequent feedings can be used to increase the likelihood of transfer of immunity, but if overfeeding problems are a concern, avoid feeding more than 2 to 3 litres in a single feed and space out feeds by at least two hours.
You can also use the Dairy Australia Colostrum Calculator to work out the optimum volume to feed. Go to: dairyaustralia.com.au/healthycalves
- Dairy Australia
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