Tuesday, September 25, 2007

Animal myths, part 1

I feel like I've be debunking a lot of animal-related myths lately, or at least encountering enough people who believe in them to make me a little uncomfortable. So, here's my attempt to clear up some confusions about animals.

  • Myth #1: Cows always produce milk.
A handful of my classmates experienced the wrath of the public during their volunteer shifts at the Miracle of Birth Center at the state fair this year. Why? They happened to be there after the birth of a calf- and when people discover that calves don't actually get to drink the milk that their moms make (aside from the colostrum), they get really upset. "Why are you taking the baby away from the mom? Doesn't he need to eat?" Well... Cows are mammals, just like humans. Female humans don't make milk until they have a baby. Cows are the same way- they won't make milk until they have calves. If we let the calf drink the milk, then what exactly would end up in the grocery store? After they consume the colostrum, calves get bottle fed a milk replacer, and cows make milk for the human food supply. It isn't healthy to make milk all the time, so after a certain amount of time, the cow gets "dried off" (stops being milked) and gets a vacation before she has her next calf and cycle starts again.

  • Myth #2: Since organic farmers can't use antibiotics, organic dairy cows aren't treated when they get sick. They keep getting milked, so the reason that organic milk tastes creamier than conventional milk is due to all the extra pus in it from those sick cows.
First, ew. Second, it's not true. Just because organic farmers can't use antibiotics preventatively doesn't mean they can't use them to treat a sick animal (obviously, it would just be cruelty to leave sick animals untreated). They also have a much longer period after antibiotic treatment before that cow's milk is allowed back into their products. Finally, organic milk has to fit within all the same health criteria as conventional milk, which includes landing within a certain "cell count". A certain number of cells in milk is normal, but elevated levels indicate that there are white blood cells in it, which means the cow has an infection in her udder. Milk with elevated cell counts isn't allowed to be sold, whether it's an organic or a traditional dairy. Milk from grass-fed cows has a different fatty acid ratio than milk from grain-fed cows, which is probably what accounts for the different texture.

  • Myth #3: Domestic dogs and wolves have identical digestive tracts.
I don't understand the logic behind this one. The myth usually takes the form of "Our dogs may look different from wolves on the outside, but inside they are indistinguishable. Thus, we should be feeding our dogs the same as we feed wolves." I'm not sure why this is so widely believed. How could you look at a pug, acknowledge its obvious external physical differences from wolves, but believe that selective breeding somehow left the GI tract untouched? One simple example compares large breed dogs to small breed dogs. Large breed dogs have a digestive tract that weighs about 2.7% of their body weight. Small breed dogs have a digestive tract that weighs about 7% of their body weight. That's a big difference! The size of the GI tract is proportionately different in small breed dogs.

If selective breeding could alter the size of the GI tract, I don't see why there couldn't be a ton of differences we simply can't recognize yet. The important thing to pay attention to is what the selective pressures have been on dogs. Early in domestication, the dogs that could survive on human garbage had a selective advantage. More recently, as diets shifted to kibble, dogs that did best on a kibble-based diet had an advantage. Kibble might only be 50 years old, but when you consider how many canine generations that is, that's a lot of time for breeders to be selecting (intentionally or not) for dogs that do well on kibble. A wolf that can't handle the bacterial load of raw meat simply dies. Dogs haven't had the same selective pressure placed on them- when Winnie had awful diarrhea after my attempt at raw feeding, I just put her back on kibble, no (long-term) harm done.

Anyway, my point is, there's almost no way that the GI tract escaped being altered throughout the many many many years of canine domestication. There's nothing wrong with that, and it addresses the important point that while wolves may be well-equipped to deal with raw meat, our dogs aren't always armed with the same protective mechanisms (that's a long way of saying that yes, dogs can get infected with E. coli and Salmonella- and keep in mind that those pathogens exist primarily in our domesticated livestock, and not as often in freshly-killed prey items in the wild...).

  • Myth #4: The life span of pets has been decreasing over recent years due to [insert paranoia of choice here].
First, no one collects data on pet life spans, so no one has been tracking this. Second, it anecdotally doesn't appear to be true. Vet clinics today are routinely seeing cats age well into their 20s, something that was remarkable a few decades ago. The same goes for dogs- one of my professors had a 16 year old Boxer (!). So I can't say for sure, since there's no real data, but I think the vast majority of animal professionals would say that pet life expectancy is longer today than ever.

The corollary to this is "Pets are developing more cancer today than 10 years ago due to kibble/flea control products/overvaccination/etc." We are seeing more cancer now than ever, but the vast majority is because pets are now getting old enough to develop cancer- and, as pets are moved out of the backyard and into the house (then the bedroom, then the bed...), owners are far more aware of their pets' health. A lipoma that an owner would never have noticed on the backyard dog is now not only noticed on the 'furkid', but called a "cancer", and results in a trip to the vet.

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