Influence of Plane of Nutrition on Body Composition, Organ Size and ...

ENERGY UTILIZATION DURING REALIMENTATION 2533DependentvariableHeart,gLiver,0.029-0.64 ±gKidney,0.370.08 ±gGut,0.063.77 ±gIntercept0.147 ±0.30Empty'Model was Y = b„+ b,EBWTABLESRegression <strong>of</strong> organ weights on body weight and rate <strong>of</strong> gain <strong>of</strong> rats1average daily gain. All weights are in grams.bodyweight0.00310.00020.053 ±0.0030.0087 ±0.00040.033 ±±0.002Averagedailygain-0.00750.00460.206 ±0.059-0.002 ±0.0090.285 ±±0.048r20.840.930.920.91BSD0.650.840.130.68+ b2ADG, where Y was organ weight, EBW empty body weight and ADGDISCUSSIONNumerous data are available from studies in which the influence <strong>of</strong> plane <strong>of</strong> nutrition on body composition and composition<strong>of</strong> gain has been evaluated. Results fromthese studies have not been consistent. Asnoted by Black (23), data are available toshow, for example, that body fat at a givenweight increases, is not affected or decreasesin response to increased energy intake.Black concluded that most <strong>of</strong> the conflictingreports could be reconciled if the interactions among plane <strong>of</strong> nutrition, chemicalcomposition <strong>of</strong> the diet, frequency <strong>of</strong>feeding and stage <strong>of</strong> maturity were considered. If other factors are constant,response to nutritional restriction is dependent on the degree <strong>of</strong> restriction, the duration <strong>of</strong> the restriction and the time afterrealimentation at which the response ismeasured.In contrast to studies reported previously,the design <strong>of</strong> this study allows direct comparison <strong>of</strong> the composition <strong>of</strong> body weightchange <strong>of</strong> animals differing in weight, but<strong>of</strong> the same age and gaining body weight atthe same rate (eg., HM, MM and LMgroups). Comparison <strong>of</strong> this type (table 5)suggested that as previous plane <strong>of</strong> nutritiondecreased, rate <strong>of</strong> protein gain decreasedbut rate <strong>of</strong> fat gain changed little. Thisdesign also allowed a direct comparison <strong>of</strong>the body composition <strong>of</strong> animals <strong>of</strong> thesame age and weight that had achieved thatweight as a result <strong>of</strong> differing growth patterns (e.g., HL, MM and LH groups, table4). Body protein content at the end <strong>of</strong>period 2 decreased and body fat content increased as plane <strong>of</strong> nutrition decreased during period 1. These results show that in thisexperiment both composition <strong>of</strong> gain duringperiod 2 and body composition at the end <strong>of</strong>period 2 were altered in response to plane <strong>of</strong>nutrition during period 1.Webster (24) concluded that any improvement in food conversion efficiencyduring compensatory growth could bealmost entirely attributed to differences inthe energy content <strong>of</strong> the gain. In the current study, energy content <strong>of</strong> the live weightgain decreased as previous level <strong>of</strong> nutritiondecreased (e.g., in males HH + HM = 3.00vs. MH + MM = 2.52 vs. LH + LM = 2.32kcal/g), which tends to add credence to thatconclusion. Also, when animals <strong>of</strong> thesegroups were compared, body protein followed a similar pattern. Commensuratewith the decrease in body protein, weobserved a decrease in the energy requirement for energy stasis. These findings areconsistent with previous reports (25-27)suggesting that basal heat production ormaintenance requirements were associatedwith body lean or body protein mass. Also,previous reports (28, 29) have shown thatprotein gain is less efficient energeticallythan fat gain. Thus, the differences in energetic efficiency <strong>of</strong> body energy gain maybe attributed to differences in the composition <strong>of</strong> gain.Other data suggest that increased efficiency during compensatory growth cannotbe attributed solely to body compositionand composition <strong>of</strong> gain (30-31). Thosedata demonstrate that maintenance requirements <strong>of</strong> steers decreased in responseDownloaded from jn.nutrition.org by guest on August 9, 2014