QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kienzle, E. Articles by Schönmeier, A. Search for Related Content PubMed PubMed Citation Articles by Kienzle, E. Articles by Schönmeier, A.

---

Supplement: The WALTHAM International Sciences Symposia Innovations in Companion Animal Nutrition: Poster Presentations

Prediction of Energy Digestibility in Complete Dry Foods for Dogs and Cats by Total Dietary Fiber^1,2

Ellen Kienzle^*,3, Vincent Biourge and Alexandra Schönmeier^*

^* Institute of Physiology, Biochemistry, and Animal Nutrition, Ludwig-Maximilians-University Munich, D-85764 Oberschleißheim München, Germany and Royal Canin, Research Center, BP4, 30470 Aimargues, France

³ To whom correspondence should be addressed. E-mail: kienzle{at}tiph.vetmed.uni-muenchen.de.

KEY WORDS: • symposium • energy digestibility • total dietary fiber • dry food • cats • dogs

Energy digestibility in dog and cat food can be predicted by the linear regression of the fiber content on a dry matter (DM) basis. Fiber is the independent variable and in vivo measured energy digestibility the dependent variable. This has been demonstrated for crude fiber (CF) in both species and in dogs for total fiber as analyzed by the Englyst and Cummings method (1,2). To date, however, few observations have been published measuring both total dietary fiber (TDF, according to the method of Prosky et al. [3]) and energy digestibility in dogs and cats. From the existing data points, it is thus not possible to 1) calculate a regression equation as for crude fiber or total fiber that is likely to predict digestibility more accurately in pet foods and 2) compare the accuracy of prediction of energy digestibility by CF and TDF methods.

	MATERIALS AND METHODS

TOP MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
In the present study 610 dog digestion trials and 261 cat digestion trials were evaluated in retrospect. The diets fed during the digestion trials included the range of fiber contents found in commercial pet foods, from reducing diets to highly digestible puppy foods or highly digestible diets for animals with gastrointestinal diseases. The range of nutrient content is given in Table 1. A total of 18 healthy dogs, intact females including different breeds ranging in size from Fox Terriers to Great Danes, and 30 healthy cats, intact female and neutered male domestic shorthairs between 2 and 10 y of age, were available for the study. Each digestion trial was carried out with a different food. The trials included an adaptation period and a collection period as recommended by the Association of American Feed Control Officials recommendations (4). Each trial was carried out with 6 dogs and 10 cats, respectively. The mean value of digestibility of all dogs or cats in 1 trial was considered to be the result of this trial. Dogs were offered a limited amount of food once daily to maintain optimal body weight; cats were given 120 g/d, which was usually not eaten completely. In both species the food that was not eaten was weighed. The adaptation period was 5 days, and feces were collected for another 5 days. All trials were approved by the Veterinary Services of the French Ministry of Agriculture. Feces were dried for 7 d (dogs) or 3 d (cats) at 60°C and then until stable weight was reached at 103°C. After grinding, DM was again determined at 103°C. Protein was determined by the method of Dumas in a Leco FP-248 Model Nitrogen Determinator (Leco). Heat of combustion in food and feces was determined by adiabatic bomb calorimetry (2 repetitions, IKA C2000, Rhys International, Ltd.). TDF was analyzed by the method of Prosky et al. (3). In 495/610 dog trials, dietary CF content was also determined by the Weende method (5). Energy digestibility was calculated according to the equation: (energy in food – energy in feces)/energy in food x 100. Linear regression equations were calculated using fiber content on a DM basis as an independent variable and measured energy digestibility as a dependent variable. In addition, the following parameters were also calculated using factors for gross energy and N-correction from NRC (6): 1) Experimentally measured digestible energy: DE_exp (kcal/g) = [Heat of combustion in the food (kcal) – heat of combustion in the feces (kcal)] / amount of food (g). 2) Experimentally measured metabolizable energy (ME_exp): dogs, ME_exp (kcal/g) = DE_exp (kcal/g) – 1.25 kcal/g digestible crude protein; cats, ME_exp (kcal/g) = DE_exp (kcal/g) – 0.9 kcal/g digestible crude protein [protein digestibility as measured in the digestibility trial: digestible crude protein = protein content in 1 g of food x protein digestibility (%)/100]. 3) Gross energy (GE) from crude nutrients: GE (kcal/g) = 5.7 kcal x g protein + 9.4 kcal x g fat + 4.1 kcal x g (N-free extract and fiber); (nutrients in g/g food). 4) Predicted digestible energy (DE_pred) from gross energy (GE; calculated from crude nutrients) and predicted energy digestibility: DE_pred (kcal/g) = GE (kcal/g) x energy digestibility/100. 5) Predicted metabolizable energy (ME_pred) from predicted digestible energy (DE_pred) and crude protein content in the food (g protein/g food): dogs, ME_pred (kcal/g) = DE_pred (kcal/g) – 1.04 kcal/g protein; cats, ME_pred (kcal/g) = DE_pred (kcal/g) – 0.77 kcal/g protein.

	RESULTS

TOP MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

View larger version (9K): [in this window] [in a new window]   FIGURE 1  Relation between TDF in DM and energy digestibility in 610 complete dry dog foods: energy digestibility = 96.6 – 0.96 x TDF (% DM), r = 0.94.

View larger version (8K): [in this window] [in a new window]   FIGURE 2  Relation between CF in DM and energy digestibility in 495 complete dry dog foods. Solid line: energy digestibility = 92.9 – 1.60 x CF, r = 0.87; dashed line: energy digestibility = 91.2 – 1.43 x CF (equation by Kienzle et al. [2]).

View larger version (9K): [in this window] [in a new window]   FIGURE 3  Relation between TDF in DM and energy digestibility in 261 complete dry cat foods: energy digestibility = 95.6 – 0.89 x TDF (% DM), r = 0.88**.

Compared with TDF, CF content in the food was systematically lower. The results of both methods showed a significant correlation (r = 0.88, Fig. 4).

View larger version (7K): [in this window] [in a new window]   FIGURE 4  Relation between CF and TDF analysis.

View larger version (8K): [in this window] [in a new window]   FIGURE 5  Relation between MEexp and MEpred by TDF in dog food: solid line, MEexp = MEpred (regression equation: MEpred = 0.45 + 0.89 x MEexp, r = 0.94).

View larger version (8K): [in this window] [in a new window]   FIGURE 6  Relation between MEexp and MEpred by CF* in dog food: solid line, MEexp = MEpred * (equation by Kienzle et al. [2]); energy digestibility (%) = 91.2 – 1.43 x CF (% DM) (regression equation: MEpred = 0.64 + 0.84 x MEexp; r = 0.95).

View larger version (8K): [in this window] [in a new window]   FIGURE 7  Relation between MEexp and MEpred by TDF in cat food: solid line, MEexp = MEpred (regression equation: MEpred = 0.50 + 0.88 x MEexp; r = 0.96).

	DISCUSSION

TOP MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

CF and TDF are different methods to assess the fiber content of diets, that is, the part of plant material that escapes digestion by the digestive enzyme of mammals (Fig. 4). CF is a method proposed >100 y ago, easy and cheap to perform, required on the label of pet food, but that seriously underestimates the fermentable fiber content of food (4,8). Most fermentable fibers have, however, a comparatively high apparent digestibility (9–11). In other words, fermentable fiber is not likely to impair energy digestibility to the same extent as nonfermentable fiber, but it is also not likely to be analyzed as CF. In contrast, some proteins may be analyzed as CF (12). The digestibility of such proteins is higher than that of CF, and they are unlikely to depress the digestibility of other nutrients. Consequently, energy digestibility of the food would be underestimated. To discriminate between CF and protein, it is recommended to determine the crude protein content in the filter residue that is supposed to be CF.

The equation for prediction of energy digestibility by CF obtained in the present investigation hardly differed from the equation obtained in a previous study (2), which is also recommended by NRC (6). Obviously, there is no need to make adjustments to the predictive equation using CF (6).

TDF is a more recent method based on an in vitro digestibility assay (3). It is more difficult to set up, more labor intensive, and thus a more expensive assay, but it gives a better estimate of the actual fiber content of the diet (9). Most fermentable and nonfermentable fibers will be included in TDF. This probably explains why, in this study, dry dog food energy digestibility was more accurately predicted using TDF than CF, and there were fewer values outside the expected range. Whether this TDF equation can be generalized to moist food, which may contain more fermentable fiber, should be investigated before a general recommendation to prefer TDF over CF for the prediction of energy digestibility can be made.

Our results suggest that both methods are useful to predict ME in dry food (Figs. 5–7). The correlation between experimentally determined ME and predicted ME by both methods in dog food and by TDF in cat food is quite good (dog food, TDF r = 0.94, CF r = 0.87; cat food, TDF r = 0.88). This is because of 1) an accurate prediction of energy digestibility by fiber (either method) and 2) a very close correlation between measured combustion heat and calculated gross energy in the food (dog food, calculated gross energy = 0.37 + 0.93 heat of combustion, r = 0.97; cat food, calculated gross energy = 0.31 + 0.94 heat of combustion, r = 0.96).

	FOOTNOTES

 
¹ Published in a supplement to The Journal of Nutrition. Presented as part of The WALTHAM International Nutritional Sciences Symposium: Innovations in Companion Animal Nutrition held in Washington, DC, September 15–18, 2005. This conference was supported by The WALTHAM Centre for Pet Nutrition and organized in collaboration with the University of California, Davis, and Cornell University. This publication was supported by The WALTHAM Centre for Pet Nutrition. Guest editors for this symposium were D'Ann Finley, Francis A. Kallfelz, James G. Morris, and Quinton R. Rogers. Guest editor disclosure: expenses for the editors to travel to the symposium and honoraria were paid by The WALTHAM Centre for Pet Nutrition.

² Author disclosure: No relationships to disclose.

	LITERATURE CITED

TOP MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 

1. Englyst HN, Cummings JH. Improved method for measurement of dietary fiber as non-starch polysaccharides in plant foods. J Assoc Off Anal Chem. 1988;71:808–14.[Medline]

2. Kienzle E, Opitz B, Earle KE, Smith PM, Maskell IE. The influence of dietary fibre components on the apparent digestibility of organic matter and energy in prepared dog and cat foods. J Anim Physiol Anim Nutr (Berl). 1998;79:46–56.

3. Prosky L, Asp NG, Furda I, DeVries JW, Schweizer TF, Harland BF. Determination of total dietary fiber in foods and food products. Collaborative study. J Assoc Off Anal Chem. 1985;68:677–9.[Medline]

4. Association of American Feed Control Officials (AAFCO). AAFCO official publication. 2003; Oxford, IN: American feed control officials.

5. Naumann C, Bassler R. Die chemische untersuchung von futtermitteln [Chemical feed analysis], Band III. Methodenbuch 1988; Neudamm: Verlag J. Naumann.

6. National Research Council. Nutrient requirements of dogs and cats. 2005; Washington, D.C.: National Academy Press.

7. Kienzle E. Further developments in the prediction of metabolizable energy (ME) in petfood. J Nutr. 2002;132:1796S–8S.[Abstract/Free Full Text]

8. Schrag I. Untersuchungen zur Bruttoenergiebestimmung an isolierten einzelfuttermitteln sowie an kommerziellen futtermitteln für hund und katze [Investigations in heat of combustion of isolated single feed stuff and prepared dog and cat food]. 1999; Diss. med. vet., München.

9. Fahey GC Jr, Merchen NR, Corbin JE, Hamilton AK, Serbe KA, Hirakawa DA. Dietary fiber for dogs: II. Iso-total dietary fiber (TDF) additions of divergent fiber sources to dog diets and their effects on nutrient intake, digestibility, metabolizable energy, and digesta mean retention time. J Anim Sci. 1990;68:4229–35.[Abstract]

10. Zentek J. Dietary fibre in dog food: comparison of cellulose, pectin and guar. J Anim Physiol Anim Nutr (Berl). 1996;75:36–45.

11. Diez M, Eenaeme van C, Hornick JL, Baldwin P, Istasse L. Dietary fibre in dogs diet: comparison between cellulose, pectin, guar gum, and between two incorporation rates of guar gum. J Anim Physiol Anim Nutr (Berl). 1997;78:220–9.

12. Schuster S. Wirkung verschiedener cellulosen im vergleich zu guarmehl auf nährstoff- und bruttoenergieverdaulichkeiten sowie kotqualität beim hund [Effect of different celluloses, in comparison with guar, on nutrient and energy digestibility and feces quality in dogs]. 2003; Diss. med. vet., München.

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kienzle, E. Articles by Schönmeier, A. Search for Related Content PubMed PubMed Citation Articles by Kienzle, E. Articles by Schönmeier, A.