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

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2528 FERRELL AND KOONGand females were observed. Protein, fat andenergy contents <strong>of</strong> those animals were related to their body weight (g) by the following equations:1) Protein, g = -1.046 + 0.1718 x BWr2 = 0.99, n = 152) Fat, g = -0.552 + 0.0546 x BWr2 = 0.85, n = 153) Energy, kcal = -11.40 + 1.527 x BWr2 = 0.98, n = 15These equations were subsequently used topredict the initial protein, fat and energycontent from initial body weight for eachanimal killed at d 21. Weights <strong>of</strong> all rats(table 2) at the end <strong>of</strong> period 1 coincidedwith the experimental design except thatfemale rats <strong>of</strong> treatment H did not achievethe desired live weight, which resulted in atreatment x sex interaction. Similarly, females on the H treatment had lower emptybody weights and contained less water, protein, ash and energy than males on the Htreatment, whereas females and males on Mand L treatments did not differ with respectto these variables. Amount <strong>of</strong> empty bodyfat differed only due to treatment(P < 0.01). Amounts <strong>of</strong> all body components increased as nutrition level increased.However, when amounts <strong>of</strong> body components were expressed as percentages <strong>of</strong> empty body weight, treatment x sex was not asignificant (P > 0.05) source <strong>of</strong> variation.Percentage <strong>of</strong> water and ash decreased(P < 0.01), percentage <strong>of</strong> fat and concentration <strong>of</strong> energy increased (P < 0.01) andpercentage <strong>of</strong> protein did not change(P > 0.10) with increased plane <strong>of</strong> nutrition. Percentages <strong>of</strong> water or ash and concentration <strong>of</strong> energy did not differsignificantly (P > 0.05) between male andfemale rats, but female rats contained agreater (P < 0.05) percentage <strong>of</strong> fat (6.0 vs.4.6%) and a lower percentage <strong>of</strong> protein(21.5 vs. 22.1%) than male rats when evalTABLE 2uated across treatment groups.The treatment X sex interaction was alsoa significant (P < 0.05) source <strong>of</strong> variationin gain <strong>of</strong> body chemical components (except fat). Male rats assigned to the H treatment gained body tissues (except fat) moreLeast squares means for metabolizable energy (ME) intake, body composition and composition oj gain ojmale and female rats sacrificed at the end <strong>of</strong> period 1groupItemNo.animalsME <strong>of</strong>kcal/d1Final intake,g3Empty live weight,g3Emptybody weight,g3Emptybody water,g4Emptybody fat,g3Emptybody protein,g3Emptybody ash,kcaPEmpty body energy,g/d1Water body gain,Treatmentg/
ENERGY UTILIZATION DURING REALIMENTATION 2529rapidly than did females, whereas gains <strong>of</strong>body tissues by male rats assigned to the Mor L treatments were less than or equal tothose <strong>of</strong> female rats assigned to those treatments.Relationships <strong>of</strong> amounts <strong>of</strong> body components to BW for rats killed at the end <strong>of</strong>period 1 were significantly affected(P < 0.05) by sex; thus regression equationshave been presented for each sex (table 3).These equations were subsequently used toestimate the weight <strong>of</strong> these componentsand energy content <strong>of</strong> rats at the initiation<strong>of</strong> period 2.The ME required for maintenance andefficiency <strong>of</strong> utilization <strong>of</strong> ME for body energy gain (EG, kilocalories per day) for allrats during period 1 were estimated by use<strong>of</strong> regression analyses. Initial analysesrevealed no significant differences betweensexes; thus data were pooled across sex togive the following result:4) EG = -47.0 x MBS + 0.53 x MEI(Â±5.7) (Â±0.03)r2 = 0.99, RSD = 1.06This equation yields an estimate <strong>of</strong> 88.5kcal/kgÂ°75for the daily ME required formaintenance and an estimate <strong>of</strong> 0.53 for theefficiency <strong>of</strong> utilization <strong>of</strong> ME for body energy gain.Mean live weights <strong>of</strong> male and femalerats <strong>of</strong> the eight treatment groups at the end<strong>of</strong> period 2 are shown in table 4. Male rats<strong>of</strong> all treatments achieved the desiredweights during this period but female rats<strong>of</strong> treatments HH, HM and MH did not.Final weights <strong>of</strong> these groups were similarand indicated that females approachedmaturity at lower weights (and at weightsless than designed) than male rats. Thefemales <strong>of</strong> the other five treatments achievedthe weights specified by design.Mean final empty body weight andamounts <strong>of</strong> body water, fat, protein and energy <strong>of</strong> male and female rats <strong>of</strong> the eighttreatment groups are shown in table 4. It isobvious that weights <strong>of</strong> the body chemicalcomponents are highly correlated withempty body weight; however, one <strong>of</strong> the objectives <strong>of</strong> the study was to compare thebody composition <strong>of</strong> animals at the sameweight and age which had achieved thoseweights through different nutritional manipulations. Therefore, the comparisons <strong>of</strong>primary interest are between treatmentsHM and MH (group 1), among treatmentsHL, MM and LH (group 2) and betweentreatments ML and LM (group 3). In malerats, there were no significant differences(P > 0.05) in empty body or water weightsamong treatments within any given group.Protein weights or percentages were lower(P < 0.05) and fat weights (or, withingroup 2, percentages) were higher(P < 0.05) for male rats within a givengroup that were on higher planes <strong>of</strong> nutrition during period 2. No differences wereDownloaded from jn.nutrition.org by guest on August 9, 2014TABLE 3Relationships <strong>of</strong> empty body weight, weight <strong>of</strong> body water, protein, fat or ash and body energyto body weight (BW) <strong>of</strong> male and female rats killed at the end <strong>of</strong> period 1SexMaleFemaleN Component13kcal11Empty gWater, body,gProtein,gFat,gAsh,gEnergy,Empty gWater, body,gProtein,gFat,gAsh,gEnergy,kcaly=y=y=y=y=y=y--6.251--4.474--6.609-1.563--53.51--9.869=y --=y --2.776 13.86=y=y=y -30.93=-9.979-3.679-1.3761.089BWh0.775BWh0.289BWh0.103BWH0.0247BWi-2.010BWh1.010BWi-0.964BWh0.260BWh0.112BWi-0.0264BWh-RÃ©gressionh0.1323BW-0.000776BW"-0.000773BW2-0.000368BW2-0.000947BW2-0.00189BW2-0.000343BW2+0.001116BW2+0.00997BWr20.990.990.990.860.980.960.990.930.990.930.960.99RSD3.353.
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