Waste milk has always been dubbed a cost-effective, nutritious feed for calves. While that's certainly true, it's interesting to note that waste milk -- and especially unpasteurized waste milk -- harbors a large number of unwanted organisms.

In fact, a 1997 study at the University of California-Davis found that the number of live bacteria in waste milk was much higher than the number of bacteria found in other types of milk, such as milk replacer.

The numbers may surprise you.

Out of 165 milk samples, researchers identified mastitis -- causing Strep species in 84, or a little more than half. And, the number of samples with Staph species fell just shy of 50 percent.

In short, every time you feed waste milk, and especially unpasteurized waste milk, you stand a good chance of exposing your calves to a significant number of bacteria and other pathogens, such as Johne's disease and salmonella.

Sure, you follow careful management practices when you feed waste milk, such as keeping it cool and storing it for short periods of time. Yet, the antibiotic residues and harmful organisms often present in waste milk can impact your calf's health.

Take a closer look at these negative impacts. It could help you change your mind about feeding waste milk to your calves.

For example, a University of California-Davis study found that 63 percent -- 119 out of 189 -- of fluid milk samples taken from 12 commercial dairies tested positive for beta-lactams or tetracycline, two groups of antibiotics detected in waste milk. Sure, calves will drink waste milk containing antibiotic residues, but that doesn't mean they like the taste of it.

According to the January/February 1990 issue of the British Veterinary Journal, calves fed waste milk containing antibiotics rejected it more than calves fed milk replacer. As a result, these calves didn't gain as well as those fed milk replacer.

In the study, calves fed milk replacer drank 4 quarts per day, whereas calves fed waste milk containing antibiotics drank 3.7 quarts of milk per day. Even though this was not a significant decrease in milk consumption, it still impacted weight gain. Calves fed the waste milk gained 0.2 per day than the calves fed milk replacer.

It doesn't end there. If you fail to pasteurize waste milk, it can impact calf performance, also.

According to a September 1996 study in Preventive Veterinary Medicine, researchers found that calves fed unpasteurized waste milk weighted 8 pounds less at 180 days of age than those calves fed pasteurized waste milk.

Thus, waste -- milk and especially unpasteurized waste milk -- can impact calf performance, resulting in slower growth and lighter weaning weights.

Harmful microbes increase dramatically when waste is stored at room temperature or above, says Jim Quigley, director of research and product development with American Protein Corporation. And, storing waste milk -- even if it's only for a short period of time -- allows harmful bacteria, such as E.coli and salmonella, to increase.

As mentioned previously, California researchers found that the number of live bacteria were significantly higher in waste milk samples compared to other types of milk taken from California dairies. For example, the researchers identified Staph species in 68 out of 165 samples.

Your cows could be exposing your calves to diseases, too. For example, cows infected with diseases, too. For example, cows infected with diseases such as Johne's disease or bovine viral diarrhea can contaminate the waste milk and pass the disease on to your calves.

Pasteurization can pay off big time by killing off most -- if not all -- of the harmful bacterial organisms. (The jury's still out on whether pasteurization destroys Johne's, although the USDA says it does.)

Pasteurizing waste milk can be economical for dairies feeding a minimum of 315 calves per day. If you don't feed this amount of calves or you don't want to spend upward of $10,000 to buy pasteurization equipment, consider feeding milk replacer instead.

1. Determine the health status of your cows, says Jim Quigley, director of research and product Development with American Protein Corporation. Don't feed waste milk if your cows are shedding organisms which cause disease, such as Johne's and bovine viral diarrhea.
2. Don't feed waste milk until two milkings after a mastitis or antibiotic treatment, says Jim Drackley, associate professor of animal science at the University of Illinois.
3. Feed waste milk only to herd replacements or to calves being kept at least eight to 12 weeks After the last feeding of waste milk, says Heinrichs.
4. Don't feed milk that is excessively bloody or has an unusual appearance since it can contain Active pathogens and white blood cells, which are difficult for a calf to digest, Quigley says
5. Consider pasteurizing waste milk. Pasteurization can be cost-effective for dairies that feed 315 calves or more per day. That means you should be milking about 1,300 cows to make pasteurization economical.
6. Don't feed waste milk to group-housed calves, Quigley says. Calves which suck on one Another can spread mastitis pathogens.

For example, if your milk is worth $13 pr hundredweight, that's your opportunity cost, or what you could get paid for selling your milk instead of dumping it. If you feed milk replacer, your cost for 1 pound of milk replacer , your cost for 1 pound of milk replacer powder runs about 80 Cents per calf per day. If you feed 10 pounds of waste milk instead, it will cost you $1.30 per calf per day. Therefore, your opportunity cost is 50 cents per calf per day. In short, that's the money your're losing by producing milk you can't sell.

Bottom line; Waste milk can be a good source of nutrition for your calves. Yet, negative factors, such as antibiotic residues and infectious pathogens, can impact your calves health and performance. That, and the fact that you lose money by producing unsaleable milk, may make you think twice about feeding waste milk to your calves.

Bacteria Flourish in Waste Milk A University of California Davis study found that waste milk samples, indicated by the blue bar, had much higher bacterial counts than other types of milk. Milk replacer (green bar), for example, contains less bacteria than waste milk, thus making it safer to feed.

Source: Journal of the American Veterinary Medical Association, Volume 211, October 15, 1997.

This article was orginally published in Dairy Herd Management/December 1998.
Editor: Tom Quaife. E-mail: tquaife@dairyherd.com