The FDA Amendments Act of 2007 mandates that the Food and Drug Administration develop ingredient, processing, and labeling standards to ensure the safety of pet food. It is of immediate concern, therefore, whether the major nutrient composition of pet foods is accurately reported on pet food labels. Some manufacturers provide the typical proximate analysis of commercial pet foods on a World Wide Web site or in pamphlets,1–3 but a guaranteed analysis on the label represents the only numeric description of the nutrient composition of most pet foods sold in the United States. Such a guaranteed analysis reports the guaranteed minimum as-fed percentage of crude protein and crude fat and the guaranteed maximum as-fed percentage of crude fiber and moisture.4 Some manufacturers also provide a guaranteed maximum as-fed percentage of ash and a few other nutrients.
The MED is also not reported on the label of most pet foods. Currently, a calorie content statement is only required on the label of foods that are described as light or some similar designation.4 A few pet food manufacturers voluntarily report the MED of pet foods on the label, on a World Wide Web site, or in pamphlets,1–3 but typically the MED of most pet foods can only be estimated by calculation from the guaranteed analysis. Some authors have suggested use of the guaranteed analysis directly to estimate MED when the actual analysis is not known,5 and this approach is currently in use on 1 Web site.a Nevertheless, use of the guaranteed analysis directly assumes that there is no difference between the guaranteed and actual analysis of a food. If this assumption is false, then the resulting estimate of MED is likely to be inaccurate and could lead to inappropriate recommendations regarding how much and what to feed an animal.
To the authors' knowledge, the size of the difference between the guaranteed and actual analysis of various pet foods has not been reported. Several state authorities determine whether the actual analysis conforms to the label guarantee but do not report a statistical summary of the differences measured. When the analysis of a food suggests that the food does not conform to the guaranteed analysis, then further testing of the food is undertaken and regulatory action may be initiated against the manufacturer by the state feed control officials. Therefore, most manufacturers would be expected to ensure that nutrient composition exceeds guaranteed minima and does not exceed guaranteed maxima. Differences in excess of nutrient composition minima would be expected to be small in situations in which adding nutrients increases costs and also to be larger in situations in which additional nutrients have to be included to provide a safety margin that allows for differences in ingredients and manufacturing conditions. Also, differences between the guaranteed and actual analyses might vary among foods intended for different species or life stages or among foods produced by different manufacturers.
The purpose of the study reported here was to compare guaranteed and measured concentrations of nutrients in commercial pet foods. The intent was to determine whether the manufacturers' guaranteed analyses differed from the measured proximate analyses of commercial pet foods, ascertain the size and variability of the differences, and compare these differences among types of food, among foods intended for dogs or cats or for different life stages, and among manufacturers and laboratories undertaking the analyses. It was also of interest to ascertain how much the difference between the guaranteed and actual analysis might affect an estimate of MED of a pet food.
Association of American Feed Control Officials
Metabolizable energy density
Association of American Feed Control Officials. 2007 official publication of the Association of American Feed Control Officials Incorporated. Atlanta: Association of American Feed Control Officials, 2007.
Case LP, Carey DP, Hirakawa DA, et al.Energy and water. In: Canine and feline nutrition: a resource for companion animal professionals. 2nd ed. St Louis: Mosby, 2000;3–14.
Cody RP, Smith JK. Applied statistics and the SAS programming language. 4th ed. Upper Saddle River, NJ: Prentice-Hall Inc, 1997.