Like all mammals, cows can only produce milk after they've had a baby. Most newborn calves in the United States are separated from their mothers within 12 hours - many immediately after birth - so the mother's milk can be marketed for human consumption. Though some dairy farmers still wean calves on whole milk, the majority of producers use milk replacer, which too often contains spray-dried cattle blood as a cheap source of protein. The chief disadvantage of blood-based milk replacer, according to the vice president of product development for the Animal Protein Corporation, is simply its "different color." Milk replacer containing blood concentrate typically has a "chocolate brown" color which can leave a dark residue on the bottles, buckets, and utensils used to feed the liquid. "For some producers," the company official remarked, "the difference is difficult to accept at first, since the product does not look 'like milk.'" But the "[c]alves don't care," he was quick to add.
The calves may not care, but Stanley Prusiner does. Prusiner won the Nobel Prize in Medicine for his discovery of prions. He was quoted in The New York Times as calling the practice of feeding cattle blood to young calves "a really stupid idea." The European Commission also condemned the practice of "intraspecles recycling of ruminant blood and blood products" - the practice of suckling calves on cows' blood protein. Even excluding the fact that brain emboli may pass into the trough that collects the blood once an animal's throat is slit, the report concludes, "As far as ruminant blood is concerned, it is considered that the best approach to protect public health at present is to assume that it could contain low levels of infectivity." Calves in the United States are still drinking up to three cups of "red blood cell protein" concentrate every day.
Michael Greger "Bird Flu: A Virus of Our Own Hatching" (2006)
