A popular dog treat could be adding more calories than pet owners realize, and possibly be contaminated by bacteria, according to a study published this month by researchers at the Cummings School of Veterinary Medicine at Tufts University and the University of Guelph.
The treat in question: the "bully" or "pizzle stick." The American and Canadian researchers analyzed the caloric density and bacterial contamination of these popular items, made from the uncooked, dried penis of a bull or steer. They also administered a survey to pet owners to assess their knowledge of these treats.
The study, published in the January 2013 issue of the Canadian Veterinary Journal, examined 26 bully sticks purchased from retailers in the United States and Canada and made by different manufacturers.
A random subset of the 26 bully sticks was tested for caloric content. These bully sticks tested contained between nine to 22 calories per inch, meaning the average six inch stick packed 88 calories—nine percent of the daily calorie requirements for a 50-pound dog, and 30 percent of the daily calorie requirements for a 10-pound dog.
"While calorie information isn't currently required on pet treats or most pet foods, these findings reinforce that veterinarians and pet owners need to be aware of pet treats like these bully sticks as a source of calories in a dog's diet," said Lisa M. Freeman, DVM, PhD, DACVN, professor of nutrition at TCSVM who is board-certified by the American College of Veterinary Nutrition.
Freeman was first author on the paper. Co-authors were J. Scott Weese, professor in the Department of Pathobiology at the University of Guelph, and Nicol Janecko, a research associate at the Canadian university.
"With obesity in pets on the rise, it is important for pet owners to factor in not only their dog's food, but also treats and table food," Freeman added.
All 26 treats were tested for bacterial contaminants. One (4 percent) of the sticks was contaminated with Clostridium difficile; one (four percent) was contaminated with methicillin-resistant Staphylococcus aureus (MRSA), a type of staph bacteria that is resistant to certain antibiotics; and seven (27 percent) were contaminated with Escherichia coli, including one tetracycline-resistant sample.
The number of treats sampled was small and not all of these bacterial strains have been shown to infect humans. However, the researchers advise all pet owners to wash their hands after touching such treats, as they would with any raw meat or raw meat diets. The very young, elderly, pregnant, immunocompromised and other high-risk individuals should avoid all contact with raw animal-product based treats and raw meat diets, note the scientists.
To learn more about veterinarian and pet owner perceptions of dog foods and treats, the research team developed a 20-question Web-based survey. The survey was posted online for public participation for 60 days and all responses were anonymous. It was completed by 852 adults from 44 states and six countries. Most respondents were female dog owners.
"We were surprised at the clear misconceptions pet owners and veterinarians have with pet foods and many of the popular raw animal-product based pet treats currently on the market," said Freeman. "For example, 71 percent of people feeding bully sticks to their pets stated they avoid by-products in pet foods, yet bully sticks are, for all intents and purposes, an animal by-product."
Another surprising finding was the large number of people who did not know what bully sticks actually were. A higher proportion of veterinarians (62 percent) were able to correctly identify the source of bully sticks as bull penis compared to general respondents (44 percent). Twenty-three percent of the respondents fed their dogs bully sticks.
Further research with a larger sample size is needed to determine whether the calorie content and contamination rate found in this study is representative of all bully sticks, or other types of pet treats, according to the authors.
Explore further: Birds 'weigh' peanuts and choose heavier ones
More information: Freeman LM, Janecko N, Weese JS. Nutritional and microbial analysis of bully sticks and survey of opinions about pet treats. Canadian Veterinary Journal. 2013; 54: 50-54.