If there is one area of calf rearing where standards have genuinely lifted over the last few years, it is colostrum.
A decade ago, plenty of people still worked on rough rules of thumb: get something into the calf, hope it suckles enough, and move on. Now the better farms are measuring, recording and checking. That change matters, because the first 6 to 12 hours of a calf’s life still do an enormous amount of the heavy lifting for health, growth and survival. DairyNZ states that newborn calves need at least 10% of bodyweight in gold colostrum within the first 6–12 hours, with a 40 kg calf needing about 4 litres, ideally split into two feeds because the abomasum only holds about 1.5–2 litres at a time. They also recommend feeding colostrum or an approved substitute for at least the first four days.
That guidance lines up well with the newer scientific review work. A 2025 systematic review concluded that high-quality colostrum can be assessed reliably using a Brix refractometer, with 22% or above indicating strong quality, and that early feeding is critical because antibody absorption falls away rapidly. The same review supports feeding roughly 8.5–10% of bodyweight at first feeding, then a second feed within 8–12 hours, alongside good hygiene and storage practices.
On farm, the real-world version is simple: every hour matters, and guessing is expensive.
A very familiar Canterbury or Southland story is the busy calving day where calves are left a bit too long because the team is flat out. The calf might still get fed “later that day,” and someone feels that should be good enough. But that delay is exactly where good systems separate themselves from average ones. DairyNZ notes that antibodies cannot be absorbed after 24 hours, and that the first 6–12 hours are the key window. The same page also links good colostrum management with less scours, lower death rates, better growth and improved lifetime productivity.
What is interesting is that the conversation has moved beyond just quantity. Better rearers now think in the “three Qs”: quality, quantity, quickly. DairyNZ’s colostrum guidance makes that explicit. Gold colostrum should ideally be over 22% Brix, calves should get enough volume, and the feeding needs to happen early. Bacteria matter too. Dirty collection buckets, poorly washed feeders, or warm colostrum sitting too long all reduce the value of what might have started as excellent colostrum.
That is one of the most important mindset changes in modern calf rearing. Colostrum is no longer just seen as “first milk.” It is now better understood as the calf’s first health programme.
If you want to know whether your own system is truly working, the answer is not to rely on appearance alone. A calf can look fine and still have had poor passive transfer. The review evidence shows that simple field checks such as serum total protein or serum Brix can help farms monitor whether calves are actually receiving enough immunity from the system in place. In other words, the best colostrum programmes are not just fed — they are verified.
Another change in rearing norms is that more farms now use Brix routinely rather than judging colostrum by colour alone. Dark yellow colostrum might be good, but measuring is better. A farm in the Bay of Plenty or Taranaki that starts Brix testing often finds out quickly that not every “good-looking” first milking is as strong as they thought. DairyNZ’s advice is clear that quality varies, and that the best available colostrum should be reserved for newborns.
There is also a practical labour message in all of this. Good colostrum systems make busy periods easier, not harder. Frozen high-quality colostrum, clearly labelled by Brix and date, cleaned gear, and a simple protocol for who gets what and when will usually outperform a more casual system run by experienced people. Skill matters, but systems matter more when everyone is tired.
For rearers buying calves rather than calving them themselves, this is still highly relevant. The best calf-buying conversations often start with colostrum. Were they fed early? How much? Was it gold colostrum? Was quality checked? Calves can only be as good as the start they had.
Practical takeaway
If you only tighten one part of your calf-rearing system this season, make it colostrum. Aim for:
22%+ Brix
4 litres or about 10% of bodyweight
within the first 6–12 hours
with clean gear and a second feed to follow
The calves that get that start are not just easier in week one. They are often the calves that keep paying you back right through the season.
