Comparative digestible energy requirements of adult beagles and domestic cats for body weight maintenance.

Digestible energy (DE) needs for body weight maintenance (BWM) of six adult Beagles and six domestic cats were comparatively assessed by using data from thirteen 14-day and nine 21-day consecutive apparent digestibility trials, respectively. In each trial the Beagles and cats were given different commercial foods, and feces were quantitatively collected excluding the first 7 days. The relationship between mean daily body weight change (delta BW) per trial and DE intake was examined by regression analysis of data for individual animals. Pooled mean (n = 6) data from 223 Beagle and 143 cats digestibility trials were analyzed by the same method. Significant (P less than 0.05) linear regressions between delta BW and DE intake were obtained (R2 = 0.43-0.93) for all individual Beagles, five of six cats and pooled mean data for both Beagles and cats. Mean (range) daily DE needs for BWM of six individual Beagles were 70 (63-78), 140 (127-146) and 173 (156-187) kcal for data scaled to kilograms, kilograms0.75 and kilograms0.67 BW, respectively. Respective values for six individual cats were 76 (56-89), 104 (86-114) and 114 (95-122) kcal. Analysis of group mean data for Beagles and cats generated daily DE costs for BWM of 76 and 66 kcal/kg, respectively, equivalent to 148 and 95 kcal/kg0.75. Thus adult cats had significantly (P less than 0.001) lower energy costs of BWM than Beagles when scaled to metabolic BW (kilograms0.75 or kilograms0.67), but not on an absolute BW basis.

Sulfur-containing amino acid requirements of growing dogs.

Three experiments were undertaken to establish the total sulfur-containing amino acid requirement of growing dogs. In experiment 1, six Labradors failed to grow normally when fed a soy isolate diet of 0.28% methionine with 0.18% cystine but grow well when the food was supplemented to either 0.57% or 0.74% methionine. In the next experiment, 12 Labradors and 21 beagles were fed the soy isolate diet containing either 0.39%, 0.57% or 0.74% methionine in the presence of 0.15% cystine for 12 weeks. Dogs fed 0.39% methionine had significantly lower body weights, nitrogen retentions, food intakes and feed efficiencies than their littermates fed the two higher levels. This diet provided 468 kcal metabolizable energy (ME) per 100 g, therefore a level of 116 mg total sulfur-containing amino acids (TSAA)/100 kcal ME was not adequate for growth. The lowest level found to be adequate was 0.57% methionine, or 154 mg TSAA/100 kcal ME, which is similar to the requirement of other young omnivores. A final experiment with a free amino acid diet indicated that a level of 117 mg TSAA/100 kcal ME while inadequate for Labradors, may be sufficient for some beagles, highlighting differences between intact protein and free amino acid diets and suggesting possible breed differences.

Assessment of endogenous nitrogen output in adult dogs of contrasting size using a protein-free diet.

The purpose of the work was to assess endogenous nitrogen output in dogs of widely contrasting mature body size and genotype. Fecal and urinary nitrogen excretion was measured during 14-day metabolic periods in 25 adult dogs of body-weight range 2.8-51.0 kg fed a protein-free, semipurified diet. Endogenous nitrogen excretion was assumed from day 8 after introduction of the protein-free diet and was measured during the final 7 days of each period. Mean (+/- SEM) endogenous urinary nitrogen (EUN), metabolic fecal nitrogen (MFN), and total endogenous nitrogen (TEN) outputs were 210 +/- 9, 63 +/- 3 and 273 +/- 9 mg/kg 0.75 per day. There were no significant effect of either sex or body weight on the magnitude of EUN, MFN or TEN outputs, however, EUN output was positively and significantly (P less than 0.02) correlated (r = 0.50) with percentage body-weight loss during the metabolic period. The mean values obtained for endogenous nitrogen output in adult dogs agreed closely with previous estimates in the literature for dogs exhibiting a narrower range (8.3-16.7 kg) of mature body weight.

The effect of meal frequency and protein concentration on the composition of the weight lost by obese subjects.

1. Nitrogen balance, weight loss and resting metabolic rate were measured in thirty-eight obese inpatients on 3.4 MJ (800 kcal)/d diets over 3 weeks. 2. All subjects were fed on 13% protein-energy in three meals/d for the first week. 3. In weeks 2 or 3, using a cross-over design, ten subjects were fed on 15 or 10% protein-energy as three meals/d; fourteen subjects were fed on five or one meal/d with 13% protein-energy; and fourteen subjects were fed on 15% protein-energy as five meals/d or 10% protein-energy as one meal/d. 4. N loss was least on the high-protein week and frequent-meal week: the largest difference was found when these effects were combined (P less than 0.001). 5. When protein-energy was held constant at 13% N loss decreased significantly (P less than 0.01) between week 2 and 3, but when the protein-energy was manipulated there was no significant N conservation in the third week. This suggests that the protein:energy value is more important than meal frequency in the preservation of lean tissue. 6. Weight loss was also least on the 'high-protein' week and 'frequent-meal' week, but this result reached significance only when the effects were combined (P less than 0.05). 7. Resting metabolic rate decreased with time but was not significantly altered by the dietary regimens. 8. Therefore, during the first 3 weeks at an intake of 3.4 MJ/d, a diet with a high-protein concentration, fed as frequent small meals, is associated with better preservation of lean tissue than an isoenergetic diet with lower-protein concentration fed as fewer meals. There was no evidence that meal frequency or protein concentration affect the rate of fat loss.

Predisposition to obesity.

65 women whose build ranged from normal to grossly obese were investigated to test the hypothesis that obese people, especially those with a genetic predisposition to obesity (manifest by early onset and family history of obesity), have a low energy expenditure. For the group as a whole, resting metabolic rate was related to obesity index, but the age of onset and family history of obesity had no effect on this relationship. The findings suggest that a familial predisposition to obesity is more likely to relate to energy intake than to energy expenditure.