Editor's note: The following information was provided by the Dairy Calf and Heifer Association and DCHA member Roy Williams.
With recent changes in U.S. government regulations regarding the use of antibiotics in milk replacers, the acidification of milk or milk replacer fed to young calves may provide calf raisers with an effective and scientifically valid alternative to the use of antibiotics as a means of significantly reducing the incidence of scours.
In the 1980s, there was considerable interest in feeding acidified milk replacer. This centered around two possibilities:
1. Acidified milk replacer did not spoil for days, so it was possible to provide the calf with free-choice feeding just by providing sufficient milk replacer in a bucket, and
2. There would be considerable labor savings if milk was only distributed every third day.
During that time, a large number of controlled studies compared calf performance, physiology and health of calves fed a "traditional" milk replacer program and a free choice acidified milk replacer program. These studies found that calves consuming acidified milk replacer would show somewhat better average gain per day than calves consuming an equal amount of "sweet" milk replacer. The studies done on acidified milk replacer that reported on calf health generally noted that calves on acidified milk replacer also had far fewer days with scours than calves consuming "sweet" milk replacer.
Finally, these studies found that a "typical" Holstein calf would drink nearly 4 gallons of milk replacer a day. One widely cited study that utilized 24-hour visual monitoring of the calves found that calves would consume between 9 and 29 meals of milk replacer in 24 hours. The cost of providing this much milk replacer to a calf on a daily basis was much higher than the cost of the labor saved, and free choice feeding of acidified milk replacer was largely forgotten in the U.S.
A 2006 study done by Turkish researchers found that calves fed acidified milk replacer suffered one fourth as many scour days as calves fed standard milk replacer. An earlier (1986) American study compared twice a day feeding of conventional milk replacer to unlimited free choice feeding of acidified milk replacer, and it is possible that the higher plane of nutrition was responsible for at least part of the observed health difference. However, this study observed one third as many scour days for calves fed free choice acidified milk replacer compared to those fed conventional milk replacer at a rate of 1 bottle (1/2 gal.) twice daily.
The acidified milk replacer pH was 4.9 in the Turkish study and 5.2 in the American study. Several different acids for use in acidifying milk replacers include citric, formic and propionic acids. Another study found that colostrum acidified with propionic acid to pH 3.9 resulted in feed refusal, but milk acidified to a pH of 4.3 was accepted.
The milk replacer acidification has been shown by direct measurements to significantly reduce the pH (increase the acidity) of the contents of digestive tract of calves. High pH levels (low acidity) in the abomasum and small intestine, such as occur after feeding milk or conventional milk replacers, has been shown to promote the rapid growth of E. coli and other bacteria, which can develop into a clinical infection and scours.
To acidify milk or milk replacer, you will need some pH test strips and propionic or formic acid (available from a veterinary product or chemical product supplier). The amount of acid will vary according to the product you are acidifying, and the concentration of the acid you are using. You want the pH to be as low as possible and still have your calves willingly consume the amount offered (generally more than 4.3, but always less than 5).