Add acid to milk or milk replacer, then feed it to calves — and let them eat as much as they want? Are you kidding?


Finnish dairy producers have been doing it with great success for years. And recently, Canadian farmers have warmed on the idea. The idea has migrated south, and now some U.S. producers are signing on to this feeding scheme that allows pre-weaned calves to nurse as much acidified milk or milk replacer as they want during a day.

Here’s the latest information about this feeding regimen.

Q: What is free-access feeding of acidified milk?

A. Free-access feeding mimics nature’s way of feeding calves, allowing them to eat several small meals per day and exhibit suckling behavior, explains Neil Anderson, veterinarian with the Ontario Ministry of Agriculture and Food. “Conventional rearing systems often limit access, restrict milk intake per meal, encourage rapid feeding or gorging, restrict meals per day or provide milk in pails (non-suckling).”

Research shows that calves allowed to suckle their mothers typically consume six to 10 meals per day and may consume 16 to 24 percent of their body weight as milk by the second week of life.

Acidification preserves the milk so it can be available at ambient temperatures for the calves throughout the day. Desired milk pH is 4.0 to 4.5 in this system, which inhibits bacterial growth.

With conventional, twice-daily feeding, there is no need to preserve the milk since you are not storing it for any length of time.

The free-access feeding system consists of a reservoir to hold the acidified milk, plastic tubing (along with a one-way valve) and nipples to deliver the milk to the calves whenever they want it.

The system operates on the same principle of keeping feed available to lactating cows at all times. “Free-access feeding provides freedom from hunger — the best medicine for milk-fed calves,” asserts Anderson.

“I was skeptical at first,” admits veterinarian Mark Thomas of Lowville, N.Y., who has several clients using free-access acidified milk feeding systems. “But, I’ve learned these systems can work very well.”

The system may be adapted for group pens or individual pens. Producers in colder climates also need to develop a means to prevent frozen milk in the winter.

Q: How is the milk acidified?

A. Many producers acidify milk or milk replacer using formic acid — the same material used to preserve hay and other feeds. The goal is to preserve milk by killing or inhibiting the growth of bacteria, yeasts and fungi. “Some producers found other acids that were more expensive and introduced challenges to the system,” says Anderson. So the recommendation is to stick to formic acid, unless using a milk replacer that already has the acid (which may be a different acid) added.

Again, the objective is to bring milk pH to 4.0 to 4.5. A recent Canadian study found that standardized plate-loop-count bacterial cultures for acidified milk at a pH of 4.2 had no bacterial growth after several hours. Meanwhile, control samples (untreated) had bacterial colonies too numerous to count over the same timeframe.

Formic acid is hazardous to eyes and skin, so take precautions when using it. For more information on how to acidify milk using formic acid, including mixing ratios, go to:

There are commercial milk replacers available that are already acidified. According to the Bovine Alliance on Management and Nutrition’s “Guide to Calf Milk Replacers,” use only an acidified milk replacer specifically recommended by the manufacturer. Do not use a product which produces a heavy sediment when reconstituted, according to the guide. These products may not reach the 4.0 to 4.5 pH as described above, but if used according to directions should work well. Monitor closely to ensure this is the case. You may need to modify your practices if you do not obtain the desired results.

Q: How do calves perform?

A. A New York research study published in the July 1986 Journal of Dairy Science showed improved gains — as much as 18.5 to 19.1 pounds by 35 days of age — among calves fed acidified milk replacer versus calves fed a conventional milk replacer. Those improved gains also came with a slightly higher cost per pound. All calves in the study reached approximately 300 pounds in about the same number of days.

However, research at Penn State University published in the August 1988 Journal of Dairy Science found that free-choice feeding of acidified milk replacer did not result in statistically significant improved growth. The researchers did note a higher body weight and slightly higher average daily gain for calves in group pens compared to calves in single pens.

Meanwhile, Canadian producers who have been using the feeding system since 2005 report that Holstein calves gain 1.8 to 2.6 pounds per day with free-access feeding. In general, these calves drink much more milk than those conventionally fed — often nearly twice as much. Calf starter and water intake is less, but resumes quickly to desired levels after weaning.

Ontario producers also indicate lower incidence of scours and reduced scours treatment with free-choice feeding of acidified milk replacer, which was also noted in the New York study as well as a 2006 Turkish study. This is especially true if the milk is fed at cooler temperatures — around 68 degrees Fahrenheit. Diarrhea is a problem for some farms when the acidified milk was fed significantly warmer than that.

“Calves are so well-supported nutritionally that we see less disease incidence,” says Thomas. “You still need to check calves daily, but you have to re-set your eyes to detect sick calves.

“We see significantly better gains and improved body condition, as compared to conventional, non-accelerated feeding programs,” he adds.

Producers report less cross-suckling of group-housed calves, too.

Q: What challenges exist with this feeding system?

A. This system is not for everyone. These systems cannot overcome poor management or bad facility design. In addition, increased respiratory disease in group housing can be a challenge for some producers, especially if ventilation and overcrowding is an issue.

It’s best to organize these systems so that your pens are all-in, all-out as much as possible. You can fill them over some period of time, says Thomas, but try to take calves all out at once. Also, it’s important to have enough space in your facilities that you don’t have to add calves to a pen if you have a disease challenge crop up.

You also need a means to ensure proper mixing and a way to mix the milk during the day to keep it from separating.

Also, increased milk consumption quickly adds up to additional calf-raising cost. Put pencil to paper before switching your feeding system, especially this year. You will need to change your weaning schedule a few weeks earlier to get the most financial benefit from increased gains, which affects your facility needs.

Setting systems up for calves reared in cold housing has also been a challenge for some producers, says Anderson.

However, all of these challenges can be overcome with a little ingenuity and innovation, he concludes.