Articles 21-30

Substrate oxidation in pigs during feeding, fasting and refeeding

A. Chwalibog, A-H. Tauson, G. Thorbek

Department of Animal Science and Animal Health, The Royal Veterinary and Agricultural University, Copenhagen, Denmark,

The aim of the present investigation was to evaluate oxidation of protein, carbohydrate and fat during feeding, fasting and refeeding.

Materials and methods
Twelve castrated male pigs of Danish Landrace were used, with six pigs being measured in the live weight range 20-25 kg (Group A) and six pigs in the range 30-40 kg (Group B). The animals were fed with an identical diet containing 154 g/kg protein and 16.5 MJ/kg gross energy. The feeding period was carried out with the pigs being fed ad libitum in six days with daily collection of feed residuals, faeces and urine and measurements of gas exchange (indirect calorimetry) during the last three days. The fasting period, consisting of four days, followed immediately after the feeding period and the gas exchange was measured each day together with daily collection of faeces and urine. In the following refeeding period the pigs were fed ad libitum in four days with daily measurements of gas exchange and collection of feed residuals, faeces and urine. There was free access to water during the whole experiment. The ambient temperature was 22 0 C and a relative humidity 60 %. Heat production (HE) and oxidation of protein (OXP), carbohydrate (OXCHO) and fat (OXF) were calculated from O2-consumption, CO2-production and nitrogen excretion in urine (UN) in accordance with Chwalibog et al. (1992).

The pattern of HE was identical in both groups with steep fall after one day of fasting followed by a moderate fall in the following days. The HE values increased during the refeeding period, being close to the feeding values by the end of the refeeding period. The lowest HE was observed at the fourth day of fasting and there was no significant difference (P>0.05) between Group A and B in relation to metabolic live weight, with the mean value 592 (SEM 21.1) kJ/kg 0.75 . Nitrogen excretion in urine was lowest on the last day of fasting and with the mean value of 226 (SEM 11.0) mg/kg 0.75 . Oxidation of protein, carbohydrate and fat in relation to the total HE showed an identical pattern for both groups. The contribution of OXP to HE was low with values between 9-11 % in the feeding and refeeding periods, decreasing to about 4 % during fasting. It is remarkable that no OXF occurred in the feeding period and during the last three days of refeeding and HE was covered entirely by OXP and OXCHO. However, there was a shift between OXCHO and OXF, with decreased OXCHO and increased OXF, from the last day of feeding to the first day of fasting and from the last day of fasting to the first day of refeeding. During the following three days of fasting no OXCHO occurred and OXF was a major substrate for HE. Assuming no influence from previous feeding on the last day of fasting energy requirement must be covered by utilization of body substrates. The values of OXF and OXP demonstrate that 140 and 200 g fat and 14 and 20 g protein were mobilized from the body reserves on the fourth day of fasting in Group A and B respectively. The 4 days refeeding period was sufficiently long to induce a complete recovery of metabolism.

Chwalibog A. Jakobsen K. Henckel S. Thorbek G. 1992. J Anim Physiol Anim Nutr 8:123-135.

Leptin, food intake and energy balance in pregnant and lactating mink (Mustela vison)

A-H. Tauson 1 , M. Forsberg 2 , A. Chwalibog 1

1 The Royal Veterinary and Agricultural University, Copenhagen, Denmark
2 Swedish University of Agricultural Sciences, Uppsala, Sweden

Leptin plays an important role in the regulation of food intake and energy balance. In pregnant animals hyperleptinemia may occur which, however, neither seems to be related to body fat content nor causes a depression of food intake. The mink exhibits a low food intake and negative energy balance during the late part of their 30 days true gestation. The objective of this study was therefore to evaluate if this was connected to a gestational hyperleptinemia.

Material and methods
A total of nine 2-year-old mink dams of the standard brown colour type were easured in consecutive one-week balance periods, each including a 22 h respiration experiment by means of indirect calorimetry in an open-air circulation system, throughout gestation and during the four first weeks of lactation. Blood sampling by venipuncture was carried out at weekly intervals, except for the period around expected implantation. The separated plasma was analysed for leptin (multispecies assay), insulin and thyroid hormones (total triiodothyronine; TT3, total and free thyroxine; TT4 and FT4). Statistical analyses were performed according to the MIXED procedure in SAS. Results are reported in relation to the following average stages of gestation/lactation: Before implantation (BEFIMP; 41 d before parturition), around implantation (IMP; 30 d before parturition), and the first, second and third parts of the true gestation (GEST1/3; 22 d before, GEST2/3; 13 d before and GEST3/3; 4 days before parturition), and the first to fourth weeks of lactation (W1; 4 d, W2; 11 d, W3; 18 d and W4; 27 d post partum).

All dams entering the experiment gave birth. The average number of kits per litter during the suckling period was 5.7. Kits gained weight at a normal rate (average weight 31 days post partum 192.1 g). The intake of metabolisable energy (ME) was high during BEFIMP, IMP and GEST1/3 (778, 828 and 768 kJ/kg 0.75 , respectively) and then declining during GEST2/3 (643 kJ/kg 0.75 ) to reach a very low level during GEST3/3 (435 kJ/kg 0.75 ). Meanwhile, heat production (HE) remained stable, ranging from 626 (GEST1/3) to 711 (GEST3/3) kJ/kg 0.75 . Hence, dams were in positive energy balance until GEST2/3 when it started to turn negative and during GEST3/3 it was clearly negative (-262 kJ/kg 0.75 ). During lactation ME intake and HE increased as lactation progressed. Plasma leptin concentrations were approximately doubled from GEST1/3 to GEST2/3, and they remained on this high level during GEST3/3 (4.1, 9.5 and 9.8 ng/ml, respectively). Immediately after parturition they declined to 4.4 ng/ml and by W4 5.3 ng/ml was recorded. Plasma insulin concentrations declined from BEFIMP to GEST3/3 and they remained low during lactation. The thyroid hormone concentrations declined during gestation, but TT4 and FT4 increased throughout W1 to W4 whereas TT3 remained stable.

The mink exhibited a marked gestational hyperleptinemia. Concomitantly, ME intake was low as well as insulin and thyroid hormone concentrations decreased, the latter findings being somewhat unexpected in relation to data from other species.

Modulation of uncoupling protein (UCPs) expression in adipose tissue, skeletal muscle, and liver in obese insulin resistant dogs

Véronique Leray, Constance Gayet, Edwige Bailhache, Lucile Martin, Henri Dumon, rigitte
Siliart and Patrick Nguyen

Human Nutrition Research Center, Nantes, France
Nutrition and Endocrinology Unit, National Veterinary School of Nantes, France

Uncoupling proteins (UCPs), including UCP1, UCP2 and UCP3, are mitochondrial proteins which are able to regulate energy balance, fatty acid metabolism and pancreatic function. Their expression can be altered by nutritional status, clinical obesity and diabetes. The tissular expression of UCPs and its modulation by long-term adaptation to hyperlipidic hypercaloric diet are still unknown in dogs. The aim of this study was to examine the UCPs mRNA expression in adipose tissue, skeletal muscle and liver in obese insulin resistant dogs.

Materials and methods:
Four healthy male beagle dogs, 3-9-year old, weighing 8.80-15 kg were studied. In order to develop insulin resistance, a high fat diet (55 % fat calories) was given at hyperenergetic level (twice the NRC 1985 recommendation) for 7 months. Insulin sensitivity was assessed by euglycemic hyperinsulinemic clamp technique. Adipose tissue, skeletal muscle and liver samples were taken at the beginning of the experiment and after 7 month on a hypercaloric diet. Total mRNA was extracted from samples and the mRNA expression of UCP1, UCP2, and UCP3 was measured by semi-quantitative RT-PCR.

In the samples of liver and adipose tissue, only UCP1 and UCP2 were expressed. The high fat diet decreased the UCP1 mRNA level and increased the UCP2 mRNA level. Only skeletal muscle expressed the three UCPs. The mRNA expression of UCP1 and UCP3 was increased after overfeeding, whereas the UCP2 mRNA level was decreased in obese dogs.

It is suggested that a modulation of uncoupling protein expression in obese overfed dogs. These results could, at least in part, explain the alteration of metabolic efficiency and the insulin resistance observed in these dogs.

Hypersecretion of TNFa a and IGF1 in the development of insulin resistance

Constance Gayet, Edwige Bailhache, Lucile Martin, Henri Dumon, Brigitte Siliart and Patrick Nguyen

Nutrition and Endocrinology Unit, National Veterinary School of Nantes, France

Obesity causes or exacerbates a lot of health problems, independently as well as in association with other diseases. Among metabolic changes that are related to this pathological status, insulin resistance (IR) has retained particular attention. The main objective of this study was to identify markers that would be easy-to-use tools to follow evolution of whole-body insulin sensitivity.

Materials and methods:
Seven beagle dogs were used. They were given a high-fat diet, at twice the NRC recommendation. Animals were weighed once a week. Insulin sensitivity was assessed using the euglycemic hyperinsulinemic clamp technique, before and during the period of high-fat hyperenergetic diet feeding. Blood was collected every two weeks for markers assays. The changes in plasma hormone and cytokine levels: leptin, insulin, cortisol, tetraiodothyronin (T4), prolactin, insulin-like growth factor 1 (IGF1), tumor necrosis factor alpha (TNFa), were then evaluated as well as changes in non-esterified fatty acid (NEFA) concentration..

Dogs put on weight (46.8 ± 7.8 % of their initial body weight; mean ± SE) in 1 ± 3 weeks. NEFA concentration significantly increased from 974 ± 94 mmol/L when lean up to 1,590 ± 127 mmol/L when the dogs were obese. There were no significant changes in the plasma concentrations of T4, cortisol, leptin, prolactin concentrations while three parameters exhibited significant changes. Postprandial insulin tended to exceed 40 µU/ml from the 10 th week. In a first step, IGF1 and TNFa increased regularly (from 0 to 265 ± 29.5 ng/ml and 134 ± 38.5 pg/ml respectively), and decreased from 27 th week on.

Feeding a high-fat diet to beagle dogs for about 21 weeks induced a weight gain of more than 45% . It has been shown that such a gain was mainly fat tissue. This dramatic increase in adipose tissue could be responsible for the hypersecretion of TNFa. At the same time, the increase of nonesterified fatty acids (NEFA) could have resulted from elevated rate of lipolysis), and may have been responsible for a decrease in insulin sensitivity, which over time, may lead to failure of the pancreas b-cells and insulin deficiency. After the 27 th week, the decrease in plasma IGF1 level could have resulted from cytokines action (especially TNFa). Moreover, it has been shown that TNFa may inhibit preadipocyte differentiation These negative effects on the adipocytes might correlate with suppression of other adipocyte genes such as those encoding cellular components that mediate the metabolic effects of insulin and/or control its own secretion.

Hepatic lipidosis in cats: new concepts on pathogenesis

Géraldine Blanchard, Bernard M Paragon, Colette Sérougne*, Jacqueline Férézou*, Fabien Milliat*, Claude Lutton*

Ecole Nationale Vétérinaire d'Alfort, Nutrition Unit, F-94704 Maisons Alfort, France
* Université Paris-Sud, Laboratoire de Physiologie de la Nutrition (INRA), F-91405 Orsay, France

Anorexia in obese cats may result in an idiopathic hepatic lipidosis (FHL). Up to date, the main hypothesis of its pathogenesis was a low secretion of very low density lipoproteins, as in lactating dairy cows with hepatic steatosis (Bauchart et al., 1996). This hypothesis was discussed after the first study of lipoproteins in cats with spontaneous FHL by Pazak (1998) who found an increment of plasma VLDL in such cats. A study of lipoproteins in cats during experimental induction of FHL allowed to describe the changes of these lipoproteins between obesity and FHL, compared to those of lean queens of same age and origin but fed at a maintenance level in order to prevent obesity development.

Materials and methods
Two groups of neutered adult queens were used, 8 to the HL group and the 4 to the Control group. Queens from HL group followed the protocol of induction of hepatic lipidosis validated by Biourge (1994) and were treated of their disease by enteral forced feeding when queens from the Control group received the same diet but at a maintenance level once a day. Blood was collected in the HL group at the beginning of the study (2 weeks after neutering), at obesity, at FHL and 10 weeks after clinical FHL when the queens were considered as treated, and at the corresponding times in the Control group thus at weeks 21, 26 and 37 respectively.

Results and Discussion
The results will be presented extensively during the oral presentation. The main results are the following : hepatic lipidosis increased plasma concentrations of triacylglycerol, VLDL and LDL, enriched LDL in triacylglycerol and HDL in cholesterol suggesting that VLDL secretion was enhanced, VLDL and LDL catabolism lowered, and lipoprotein exchanges impaired in FHL, as summarized in figure 1.

Figure 1:
Pathogenesis of FHL : hypothesis on lipoprotein metabolism
FA fatty acids ; LPL lipoprotein lipase ; TG triacylglycerol ; Chol cholesterol ; apoB100 apolipoprotein B100 ; CETP cholesterol ester transfer protein; VLDL very low density lipoproteins ; LDL low density lipoproteins ;HDL high density lipoproteins

Biourge VC, Groff JM, Munn RJ Kirk CA, Nyland TG, Madeiros VA, Morris JG, Rogers
QR (1994) Experimental induction of hepatic lipidosis in cats. Am J Vet Res 55, 1291-1302

Early effects of neutering on the energy intake and expenditure of domestic cats (Felis catus)

R.C. Backus * , M. L. Kanchuk, J.G. Morris, Q.R. Rogers

Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, USA

Undesired body weight gain and increased risk for obesity result from the neutering of domestic cats. The disturbance of energy balance that drives the weight gain is unclear. In the current study, energy intake and expenditure were determined in 10 adult (2 y) male cats from food intake and 12-day double-label water washout measurements, respectively. The cats were kept in individual cages (0.67 m 2 ) in a light and temperature (23±2°C) controlled room and continuously provided a commercial dry-type diet (ME=16 kJ/g) expected to produce an RQ of 0.85. After baseline measurements were conducted in all cats (12 d), half of the cats were neutered. A second 12 day double-label water washout procedure was conducted 17 days later. During the trial, food intake, body weight, and body composition were determined daily, weekly, and once during each washout period, respectively. The baseline observations on energy expenditure (296±11 kJ/kg), food intake (74±4 g/d), body weight (4.7±1 kg), lean mass (4.3±1 kg), and fat mass (0.3±0.0 kg) were not significantly different between the two groups. Energy intake (food intake x diet energy density) of neutered cats increased (p<0.05) an average of 37±6 % above pre-neuter levels and was greater than energy intake of intact cats, beginning the second post-neuter day and continuing through the second washout period. In contrast, from days 17-29 post neutering, energy expenditure in the neutered cats (332±32 kJ/kg) was not significantly different from pre-neuter levels (296±16 kJ/kg) nor levels found in intact cats during the first (296±16 kJ/kg) and second (353±13 kJ/kg) washout periods. During the trial, body weight slightly increased (6.7±2.5 %, p<0.06) in neutered cats but was unchanged in intact cats. Although rodent studies show that reduction in metabolic rate contributes to gonadectomy-induced weight gain, the present research shows that weight gain caused by the neutering of cats is driven by an immediate rise of food intake after neutering, without substantial change in energy expenditure. The mechanism of the effect of neutering on food intake should be determined.
Supported in part by the Center for Companion Animal Heath, University of California, Davis, Calif., and the Ralston Purina Company, St. Louis,

Effect of ad libitum feeding on body weight and blood metabolites in spayed female beagle dogs

Jeusette 1 , J. Detilleux 2 , C. Cuvelier 1 , L. Istasse 1 , M. Diez 1

1 Animal Nutrition Unit, 2 Quantitative Genetic Unit, Veterinary Faculty, University of Liege, B-4000 Liege,Belgium

Ovariohysterectomy can result in significant weight gain in bitches fed ad libitum (Houpt, 1979). The aim of this study was to determine the effect of ad libitum feeding on weight gain and blood metabolites in spayed female Beagle dogs.

Materials and Methods:
Four young adult 2 year-old female beagle dogs were ovariectomized. First, the amounts fed of a commercial maintenance diet was adjusted during 26 weeks to maintain stable body weight (BW) (period I). Then, a high-energy commercial dog food (Royal Canin Energy Croc, crude protein 30 %, fat 20 %, ME 3890 kcal/kg as fed) was fed in large amount during 16 weeks (period II). The amount offered was twice the amount that maintained BW. Food left uneaten after 1 hour was collected and weighted. Cholesterol, triglycerides, glucose and insulin were measured every 2 weeks during period II.

During period I, dogs received (mean ± SEM) 120.9 ± 2.5 kcal/ kg BW 0.75 to maintain BW. Mean BW at the end of this period was 13.3 ± 0.4 kg. When a high energy food was allowed in double amounts, dogs spontaneously ate significantly (p<0.05) more food with food amounts corresponding to 181.9 ± 5.4 kcal/ kg BW 0.75 . At the end of the second period, mean BW was 16.7 ± 0.8 kg, which represents a significant increase (p<0.05) of BW of 21.9 %. Period II can be divided in 4 subperiods of 4 weeks. Each subperiod was compared with period I for statistical analysis. The first four weeks, mean energy consumption was 211.5 ± 9.4 kcal/ kg BW 0.75 (p<0.01) and dogs consumed all the proposed food. Then, the ingested amounts decreased spontaneously. Mean energy consumption was 180.6 ± 12.5 (p<0.01), 176.1 ± 9.9 (p<0.01), 159.6 ± 7.2 (p<0.05) kcal/ kg BW 0.75 , for each subperiod respectively. No significant effect was seen on blood metabolites during the second period.

Ad libitum feeding induced overconsumption and subsequent weight gain in spayed female beagle dogs. This overconsumption was observed during 16 weeks (length of the study) but was more important during the first 4 weeks. It seems that ad libitum feeding induced no significant effect on blood metabolites during the study.

Houpt K.A. et al., 1979. J Am Vet Med Assoc 174: 1083-1085.

Evaluation of several home made diets for food allergy in dogs or obesity in cats

M.Hesta, J. Debraekeleer, S. Millet, L. Wilmaerts and G.P.J. Janssens

Laboratory of Animal Nutrition, Ghent University, Belgium

Although a lot of commercial therapeutic diets are available, a homemade diet can be indicated in certain cases. Only 15% of the Belgian veterinarians never prescribe a homemade diet (De Smet and Poels, 1995). Even though many recipes for home made diets can be found in the literature, Roudebush and Cowell (1992) found 90% of the home made elimination diets prescribed by 116 veterinarians not adequate for adult maintenance of dogs and cats. If the recipe meets the requirements, problems are still possible if the owner does not follow the guidelines of the veterinarian. Substitutions are frequently made and on a long-term basis vitamin and mineral supplements are often omitted. Eight recipes from the literature were prepared for two indications: food allergy in dogs (3), obesity in cats (4)1,3,4,8 . A low residue diet for dogs was also prepared 2 . Two other formulations (food allergy in dog and obesity in cat) were prepared by the owners 4 months and several years after prescription in practice. The homemade diets were analysed for weende components and Ca, P, Na and K were analysed by ion chromatography. Ingredients and proportions: One diet for cats had no carbohydrate source with consequently a high protein content. Two diets for cats had no supplemented fat source; one of them having a low analysed fat content. All diets contained animal protein sources. All recipes contained a supplemental calcium source but two recipes did not mention the addition of a multi vitamin/mineral supplement. The analysed diets were compared with the recommendations for adult maintenance (AAFCO, 2002; Hand et al., 2000) One diet for cats contained only 16% protein on DM basis and another contained 78%. Even if the lower energy intake is taken into account the protein content of the high protein diet is still high and the low protein diet is below the NRC (1986) minimum. One diet for cats had a low fat content (4.0%DM), which could predispose to essential fatty acid deficiency. All other diets were between the recommended 7-14% fat for obesity treatment in cats (Hand et al. 2000). None of the obesity diets had high fibre contents. One diet for cats and one for dogs had a low calcium content (0.25 and 0.49%DM). On the other hand one diet for dogs and three diets for cats had rather high Ca contents (1.12 to 1.92%DM) although below the maximum of AAFCO. One diet for cats had a rather low P (0.4%DM) content and three diets for cats and two for dogs had a high P concentration (1.0-2.1% DM) although part of the P may not have been available in one diet since bran (phytic acid) was added. Three of the cat diets had a too low Ca/P ratio (0.52/1 to 0.69/1) and one dog diet had a higher Ca/P ratio (2.2). Provided an adaptation of Ca and/or P supplementation in some diets and the addition of a multivitamin/mineral supplement in one diet, all diets for dogs are useful. On the contrary 2 diets for cats are not adequate at all (too low or too high protein content). One is useful if Ca, P and fat are supplemented. In two other diets a lower Ca and/or P supplementation is justified.

1 Brown et al. 1995, Comp. Cont. Ed. Pract. Vet.17, 637-658
2 Hand et al. 2000, Small animal clinical nutrition 4th ed.
3 Kronfeld 1986, tijdschrift voor diergeneeskunde111, 137S-141S
4 Meyer 1990, Ernärhung des Hundes p227
6 Roudebush and Cowell 1992, Veterinary Dermatology 3, 3-28
7 Souci et al. 1986-1987 Food composition and nutrition tables
8 Strombeck 1999 Home prepared dog and cat diets: the healthfull alternative p217-236

Evolution of blood parameters during weight loss in experimental obese Beagle dogs

M. Diez 1 , C. Michaux 2 , Jeusette 1 , C. Cuvelier 1 , C. Tonglet 1 , L. Istasse 1 , V. Biourge 3

1 Animal Nutrition Unit, University of Liège, Belgium 2 Genetic , University of Liège, Belgium 3 Royal Canin, Centre de Recherche, Aimargues, France

The objectives of this study was to measure the effects of weight loss on blood parameters in 8 adult experimental obese Beagles (4 neutered males and 4 intact females, 5.5 (range 4-7) years) fed either a high protein, low starch and high fibre dry expanded diet –DP -(crude protein 44.1 %, fat 8.7 %, crude fibre 10.0 % -as fed) or a commercial moderate protein, high starch and high fibre dry diet -HF- (crude protein 21.6 %, fat 7.7 %, crude fibre 21.0 % -as fed). The dogs were allotted into 2 groups matched for sex, body scores and body weight (BW) at baseline and were fed either the DP or control HF diet for 12 to 26 weeks, until they reach their optimal BW (Diez et al., 2002) Dogs underwent hormonal and biochemical evaluation monthly (carnitine, creatinine, urea, free T4 (FT4), total T4 (TT4), plasma alkaline phosphatases (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), potassium, total proteins) or bimonthly (cholesterol, triglycerides, non-esterified fatty acids (NEFA), IGF1, glucose, insulin) over the whole study. Blood parameters were assayed by standard procedures and results were analysed by SAS Mixed Procedure for longitudinal data with treatment (diet) and sex as fixed effects.

Dogs reached their optimal BW within 12 to 24 weeks for the HF group and 21 to 26 weeks for the DP group (Diez et al., 2002).
Before weight loss, plasma triglycerides and cholesterol concentrations were respectively (mean ± SEM) 0.75 ± 0.02 and 2.49 ± 0.02 g/l for the obese dogs. The 2 diets decreased the plasma concentrations of these 2 metabolites but the difference was only significant for the DP diet. The basal plasma mean NEFA concentration was 0.40 ± 0.03 mM/l and increased regularly over the period with the HF diet but the difference between the 2 diets was not significant.
Over the weight loss, mean plasma carnitine concentration ranged between 21 ± 2.08 and 28.3 ± 4.9 mM/L with no difference between the diets. Mean urea and creatinine plasma concentrations ranged respectively between 0.185 ± 0.01 and 0.358 ± 0.04 g/l and between 7.4 ± 0.4 and 9.9 ± 0.7 mg/l without difference between the 2 diets. No effect of diet was observed on overnight fasted plasma ALP, AST, ALT, potassium, TT4, FT4, IGF1, glucose and insulin which remained constant over the weight loss period. Blood urea and IGF1 concentrations were significantly higher in females than in males over the study (P<0.05). Weight loss induced a decrease in FT4 plasma concentrations: 12.5 ± 0.7 ng/l in obese dogs versus 7.7 ± 0.6 ng/l at the end of the weight loss (P < 0.001). Mean plasma concentration of ALP was higher in males than in females (P < 0.05). In conclusion, there was only an effect of diet on plasma cholesterol and triglycerides levels. Weight loss induced significant decreases in plasma cholesterol, triglycerides and FT4, whatever the diet offered. Based on blood parameters, at the tested energy intake, both diets assured a safe weight loss.

Diez M. et al., 2002. J. Nutr. 132 S (in press)

High fat/high energy diets and body weight regulation in cats

V. Riou 1 , C. Jean 1 , A. Patil 2 , E. Rowe 1

1 Nestle Purina R&D Centre, Amiens, France 2 Nestle Purina Product Technology Center, St. Joseph, MO, USA

Most animal species overeat when given unlimited access to a highly palatable, high-energy foods, and deposit the excess calorie intakes as body fat stores. It is unclear whether cats can regulate their energy intake to maintain body weight when given foods differing in energy content. This study investigated the effect of ad libitum feeding of extruded dry cat foods differing in energy content on body weight regulation. Thirty-seven cats 2-13 yrs old were allocated to two groups matched for body weight and food intake following a stabilisation phase (3 weeks) on dry cat food. Group one (n=18) was fed a low fat dry cat food (32% protein, 10% fat, and 3.2 kcal/gram) and group two (n=19) was given a high fat dry cat food (32% protein, 20% fat, and 4.0 kcal/gram) for a period of 11 weeks. Food intakes were recorded daily, body weights twice weekly, and body condition was scored every three weeks by double blind veterinary examination on a 1-4 point scale from very thin (1) to obese 4). Girth and limb measurements were done at 11 weeks to predict body fat content. Cats fed the high fat diet gained significantly (p<0.01) more (9.4%) body weight than cats fed the low fat diet (2.8%). Food intakes did not differ significantly between the groups with cats in group two eating slightly more calories (248 kcal vs 237 kcal/day) and slightly lower food volume (63 vs 71 grams/day). The profile of individual body weight changes in cats fed the high fat diet showed that 3 cats had excessive weight gain (> 15 %) and 7 cats gained 10-15% of their starting weights. Only 25% cats maintained their body weights (+/- 5 %). These changes in weight gain were reflected in increases in subjective body condition with 52% of cats consuming the high fat diet rated overweight or obese. The high fat fed group also had significantly higher (p<0.05) levels of body fat at the end of the trial (29.8%) than the control group (26.4 %) as assessed from girth and limb measures. Cats receiving the high fat food were then switched to the low fat diet; intakes and bodyweight changes were measured for an additional 9 weeks. These cats lost an average of 207 g body weight over this period primarily associated with a reduction in energy intake (248 kcal to 196 kcal/day). Therefore, consumption of a high fat, high calorie dry cat food can override calorie regulating mechanisms in most adult cats and can lead to weight gain and increased fat deposition.