Body weight and composition indices, and selected serum biochemistries from serum biochemical profiles, of dogs at baseline (initial) and after consuming control^* or treatment foods for 194 days (mean ± SEM).

*<p>PrescriptionDiet® k/d®, Hill’s Pet Nutrition, Inc.</p>†<p>Body mass and composition were determined by dual-energy X-ray absorptiometry scan analysis.</p

Carnitine metabolites of dogs after consuming control^* or treatment foods for 194 days.^†

*<p>PrescriptionDiet® k/d®, Hill’s Pet Nutrition, Inc.</p>†<p>Using serum values from baseline, each animal served as its own control. Data are presented relative to baseline as fold change. All data were log-transformed prior to statistical analysis.</p>a<p>Indicates significantly increased or decreased fold-change between the diet group shown and baseline at <i>P</i><0.05.</p>b<p>Indicates fold-change values that are trends but missed the significant cutoff (<i>P</i>>0.05, <i>P</i><0.10).</p

Relative ratios of serum concentrations of selected fatty acids and carnitine metabolites in geriatric dogs (>7 yr) vs. mature adult dogs (≤7 yr) at baseline (initial) and after consuming control^* or treatment foods for 194 days.

†<p>The ratios are the average concentration of an analyte for dogs in the geriatric group divided by average concentration of the same analyte for dogs in the mature adult group.</p>§<p>Because there was no age by diet interaction, concentrations for dogs consuming different diets are combined across time.</p>a<p>There was a significant effect of age on these ratios (<i>P</i>≤0.05).</p>b<p>There was an effect of age on these ratios (<i>P</i>>0.05, <i>P</i><0.10).</p>*<p>^{,£, ¥, ¶,#,‡} See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049510#pone-0049510-t001" target="_blank">Table 1</a> for rest of key.</p

Food composition of pre-trial food, control food^*, and two dietary treatment foods.^†

*<p>Prescription Diet® k/d®, Hill’s Pet Nutrition, Inc.</p>†<p>All analytical values are expressed as percentage of food as fed, unless otherwise indicated.</p>§<p>Calculated from analyticals using modified Atwater numbers (kcal/g of 3.5 for protein, 8.5 for fat and 3.5 for nitrogen free extract).</p>£<p>Sum of the saturated fatty acids: 8∶0+10∶0+11∶0+12∶0+14∶0+15∶0+16∶0+17∶0+18∶0+20∶0+22∶0+24∶0.</p>¥<p>Sum of the monounsaturated fatty acids: 14∶1+15∶1+16∶1+17∶1+18∶1+20∶1+22∶1+24∶1.</p>¶<p>Sum of the polyunsaturated fatty acids: 18∶2(n-6)+18∶3(n-6)+18∶3(n-3)+18∶4(n-3)+20∶2(n-6)+20∶3(n-6)+20∶3(n-3)+20∶4(n-6)+20∶4(n-3)+20∶5(n-3)+21∶5(n-3)+22∶2(n-6)+22∶4(n-6)+22∶5(n-6)+22∶5(n-3)+22∶6(n-3).</p>#<p>Sum of the (n-6) fatty acids.</p>‡<p>Sum of the (n-3) fatty acids.</p

Relationship between measured metabolizable energy (ME) concentrations (x-axis) and ME concentrations predicted using National Research Council (NRC) equations [2] (y-axis) for dog and pet foods.

<p>Ideally, all points should be on the line <i>x</i> = <i>y</i>. <b>A</b>) Measured ME concentrations were determined from 331 total digestibility studies in dogs, of which 259 used dry dog foods and 72 used canned dog foods. The NRC equations for dogs first calculate gross energy (GE) using the equation GE  = 5.7× g protein +9.4× g fat +4.1× (g NFE + g fiber). Energy digestibility coefficients are then calculated for dogs as (91.2–1.43× percentage crude fiber in DM). These digestibility coefficients then allow calculation of digestible energy (DE) in dogs as DE  =  GE × percentage energy digestibility/100 and, subsequent calculation of ME as ME  =  DE – (1.04× g protein). <b>B</b>) Measured ME concentrations were determined from 227 total digestibility studies in cats, of which 173 used dry cat foods and 54 used canned cat foods. The NRC equations for cats first calculate GE using the equation GE  = 5.7× g protein +9.4× g fat +4.1× (g NFE + g fiber). Energy digestibility coefficients are then calculated for cats as (87.9–0.88× percentage crude fiber in DM). These digestibility coefficients then allow calculation of DE in cats as DE  =  GE × percentage energy digestibility/100 and, subsequent calculation of ME as ME  =  DE – (0.77× g protein).</p

Food composition, expressed as means and standard deviation (SD), of canine foods used in digestibility studies.^*,†

*<p>All analytical values are expressed as percentage of food as fed, unless otherwise indicated.</p>†<p>Food composition of the experimental foods was determined by a commercial laboratory (Eurofins Scientific, Inc., Des Moines, IA) using AOAC methods.</p

Digestibility coefficients, expressed as means and standard deviation (SD), of feline foods used in digestibility studies.^*

*<p>All analytical values are expressed as percentages.</p>a,b<p>Means with different superscripts in the same row are different (<i>P</i>≤0.01).</p

Food composition, expressed as means and standard deviation (SD), of feline foods used in digestibility studies.^*,†

*<p>All analytical values are expressed as percentage of food as fed, unless otherwise indicated.</p>†<p>Food composition of the experimental foods was determined by a commercial laboratory (Eurofins Scientific, Inc., Des Moines, IA) using AOAC methods.</p

Metabolizable energy (ME; kcal/kg; means and standard deviation, SD), were determined in feline digestibility studies and compared to those calculated using predictive equations.

a<p>Predicted ME using equation with modified Atwater factors <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0054405#pone.0054405-AAFCO1" target="_blank">[4]</a>.</p>b<p>The difference between measured and estimated ME.</p>c<p>The absolute value of the difference between measured and estimated ME.</p>d<p>Predicted ME using NRC <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0054405#pone.0054405-NRC1" target="_blank">[2]</a> equations.</p>e<p>Predicted ME using equation developed from the experimental animal feeding studies.</p

Relationship between measured metabolizable energy (ME) concentrations (x-axis) and ME concentrations predicted using new study-derived equations (y-axis) for dog and cat pet foods.

<p>New study-derived equations were derived from measured ME concentrations in the animal feeding studies. These equation sum coefficients multiplied by gross energy (GE), fat, crude fiber, protein, and moisture percentages. Ideally, all points should be on the line <i>x</i> = <i>y</i>. <b>A</b>) Measured ME concentrations were determined from 331 total digestibility studies in dogs, of which 259 used dry dog foods and 72 used canned dog foods. For the dog: ME  = 575+0.816× GE (kcal/kg) +12.08× percentage fat –52.76× percentage crude fiber –20.61× percentage protein –6.07× percentage moisture. <b>B</b>) Measured ME concentrations were determined from 227 total digestibility studies in cats, of which 173 used dry cat foods and 54 used canned cat foods. For the cat: ME  = −541+0.923× GE (kcal/kg) +14.68× percentage fat –44.31× percentage crude fiber –4.21× percentage protein +4.80× percentage moisture.</p