Here's a letter from the Harlan nutritionist:
"Thank you for your email. I am one of the nutritionists at Harlan Teklad. I am not a salesperson and you will not get sales spin from me. You are correct about the quality of our diets. We manufacture our diets using the same formulas each and every time. We have standard operating procedures that we follow with each and every production. We test our ingredients when they arrive to our production facilities and we audit our suppliers. So you can rest assured that when you feed our diets to your pets, that you are feeding a consistent and quality diet. Much of what Dux said is correct although some of the facts are not quite right or need clarification. First, Harlan Teklad manufactures diets specifically for laboratory animals. Our diets were never designed with the pet food industry in mind. We have never promoted our diets for pet mice and rats nor do we know much about this industry. In fact, until recently I was not aware of how well known our products were in the pet mouse and rat industry. Upon receiving quite a few emails from rat and mouse enthusiasts such as yourself, I did a little research on-line and was shocked at how many websites existed for rat and mouse enthusiasts and of how well known our products are. It was indeed an eye opener for me. So when Dux writes that our diets were not designed with the enthusiast in mind she is correct. However, we have many diets for mice and rats with different levels of nutrition, designed for different purposes and it is not accurate to paint them all with a broad brush as was done. We have over 22 diets for mice and rats. Some were formulated for breeding animals, some for general purpose (breeding and non-breeding), and others for rodents on long term (2 year) studies. First, one has to understand that many of these diets were formulated 15-20+ years ago when there was very little known about the nutritional requirements of mice and rats. To ensure that nutritional deficiencies did not occur the "more is better" approach was followed where diets were formulated to obtain nutrient levels that were known to prevent deficiency signs. Over-nutrition was not viewed as much of a concern compared to malnutrition, especially when feeding mice and rats on short studies. Thus many traditional rodent diets contain more protein that is required. Excessive protein can cause kidney damage in aging mice and rats. So excessive dietary protein can be a problem. Most lab animal diets like commercial diets for pigs and chickens are supplemented with vitamins and minerals to prevent deficiencies. Most food for human consumption is supplemented with the same vitamins. The supplemental vitamins do not harm the animal. They are not inherently bad as Dux would suggest.
Today we know much more about the nutritional requirements of mice and rats than be did when most diets were formulated. A breeding rat or mouse only needs about 18% crude protein and a non-breeding adult rat only needs about 9% crude protein or perhaps less. Yet most of our traditional diets contain 22-24% protein. In 2000 we launched a new range of diets which we called our Global Diets because they are available in both the U.S. and Europe. The Global Rodent Diets are 2014, 2016, 2018, and 2019. When these diets were formulated the present knowledge of the nutrient requirements of mice and rats was taken into consideration. Diet 2014 was formulated for non-breeding rodents on long-term studies (2 year). This diet has a low protein content of only 14%. Excess protein can cause kidney damage in aging mice and rats. Mice and rats that are not actively breeding do not require as much protein so it is appropriate to feed this diet to rodents on long-term studies rather than diets that contain 19-24% protein. Diet 2016 was designed quite honestly for customers who were afraid to feed a diet with only 14% protein. It is difficult to get customers who have been feeding 19-24% protein diets to switch to 14% protein but they might warm up to 16% protein, thus 2016. Diets 2018 and 2019 were designed for breeding mice and rats. These animals require more protein and energy to support gestation and most importantly lactation. Diet 2018 contains 18% protein and 6% fat. Diet 2019 contains 19% protein and 9% fat. Increasing protein potentially can harm the kidneys of aging mice and rats but it does not make mice and rats fat. In fact, it has a slight negative effect on weight and fat composition (remember the Atkins diet). Energy intake by the mouse or rat controls body weight and fat deposition. Diets 2014 and 2016 contain about 4% fat while diets 2018 and 2019 contain about 6% fat and 9% fat respectively. So diets 2018 and 2019 contain slightly more energy than 2014 and 2016. Mice and rats fed diets 2014 or 2016 may put on less weight than mice and rats fed 2018 and 2019 over the long term. But it is not the protein content that is responsible. It is the increase in fat and thus the increase in energy content of the diet that is responsible for weight gain and increase fat deposition.
What are my suggestions when it comes to maximizing the life expectancy of your mouse or rat? Well, Dux hit this one right on the head. Excess weight gain is the enemy of longevity in mice and rats as it is in humans and all mammals. Excessive body weight will accelerate the onset of the diseases associated with old age which for many mice and rats is cancer. Long-term studies with mice and rats show that when the animals are restricted to 2/3 of what they would normally eat when allowed unlimited access to food that they live longer and the diseases associated with old age occur at a later age. If I had pet rats or mice, I would feed them diet 2014. It has a low level of protein compared to all other diets. Remember excess protein can cause kidney damage in aging mice and rats. Diet 2014 contains enough fat to meet the requirements for essential fatty acids but less fat than most other diets so the energy content is lower than most other diets as well. This diet was designed to be fed to mice and rats on long-term 2-year studies. Essentially the aims of the researcher feeding the diet to their research animals are closely aligned with the aims of the rat or mouse enthusiast. Avoid high calorie supplements such as nuts, chips and other junk foods which while tasty, encourage excessive weight gain. The mice and rats may still get fat on 2014 as they age. In general mammals given unlimited access to food increase their weight as they age. You can seek to restrict the diet if you wish or you can supplement their diet with high fiber foods such as fruits and vegetables. High fiber foods will fill their stomachs making them feel full but contributing little to their energy intake. However, make sure that in feeding these high fiber supplements that you do not displace the diet by more than 33%. The animal is relying on the diet to meet its nutrient requirements. The supplements are for enrichment and an attempt to reduce excessive weight gain. Also, place items in the cage which decrease boredom. If I put you in a room with nothing to do, but with food always available you are going to spend a great deal of time eating and drinking too.
In closing I just want to remind you of something that you already know. Mice and rats have a short life expectancy. By controlling body weight gain through energy restriction you are adding at best a few weeks or months on to their lives. But, the quality of their lives may vastly improve which I would say is what is truly important. Also, if you are breeding I would recommend 2018. Do not feed 2014 to breeding mice and rats. It is too low in protein and will lead to deficiency.
Sincerely,
Chuck Benton, Ph.D.
Nutritionist/Technical Services
