Barnes, P.M.

de Bruin, D.S.

Hofmeyr, H.S.

Olver, M.D.

Roux, C.Z.

Scholtz, M.M.

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S . A f r . J . A n i m .  S c i .  i , 1 , 9 9  -  1 0 0 ( 1 9 8 | )RESEARCH NOTETHE LIKELY EFFICMNCY OF PRENATAL ENERGY UTILIZATIONN, l .M.  Scho l tz ,  D .S.  de  Bru in ,  M. I ) .  O lver ,  C .Z .;1^D.5.R"1., Private Bag X2, Irene(Key words: Prenatal ef!=rciency )(Sleutelwoorde: Voorgeboortelike doelteffendheid)When analysing experiments involving the quantif icationof animal growth and efficiency of feed utilization(Parks ,  1970,  1972;  1973;  1975a; .  1975b;  Me issner ,Roux & Hofmeyr ,  I975;  Roux, I976;  Me issner ,  1977,Kemm,  1980;  Scho l tz  &  Roux.  1980)  the  cumula t iveenergy intake is required, since the mass of an animal atany stage is a function of the total amount of feedconsumed up to that stage. trn evaluating the relationshipbetween cumulative feed intake and body mass at birth,for example, the energy input to achieve birth mass isnot known and methods are required to estimate this.A solution to this problem is to estimate the energycontent of the animal body at birth e.g.by the use ofa regression equation relating birth mass and bodyenergy, and to correct this value for prenatal efficiencyas follows:. l0O% + prenatal efficiency x body energyat birth = total energy input for birth mass. Estimates ofthe prenatal efficiency of energy utilization are thereforeneeded to solve this equation.ln mammals these estimatesare difficult to obtain because the maternal organismundergoes profound metabolic changes, so that the heatincrement of gestation is by no means the heat productionof the embryo and foetus. Furthermore, the embryo,or foetus constitutes only a small part of the motherwhose metabolism is measured. so that measurementerror may be of the same magnitude as the embryoniccontribution. The situation is further complicated if themother is young and growing (Brody, 1945).According to Brody (1945) the bird embryo is part icu-larly suited for prenatal growth efficiency investigation.This is because in the case of eggs the nature of thenutr ients is known, and eggs are convenient ly isolatedfrom complicating environments. The gross energeticefficiency of growth of the bird up to the time of hatch-ing can be obtained by estimating the combustion valuesof  ( l )  the  egg,  (2 )  the  newly -ha tched b i rd .  and (3 )  theunused part of the egg, such as the left-over yolk andmembranes.Efficiency figures available from published literaturevary from 85 percent for newborn lambs (Kielanowski,Receipt of MS 08-12-80Roux, H.S. Hofmeyr and Penelope M. Barnes1675, Republic of South Afica1965) to 62 percent for chicks. 65 percent for silk-worrns, 59 percent for the sea urchin and 5l percentfor f iogs (Brody, 1945).  Brody (1945) favoured anefficiency value between 60 and 65 percent. This studywas intended to investigate whether the efficiencyfigures for the largest living bird (the ostrich) wouldcorrespond to the range of values given by Brody(1945).The question arises from Brody's (1945) conclusionthat, in general, prenatal efficiency does not vary withsize or incubation time.Four dozen ostrich eggs were obtained of which l0 wereused to estimate the combustion value of the egg byadiabet ic bomb calor imeter,  and 38 were hatched in anincubator. Of the latter 30 were inferti le, 6 died duringincubation, while only 2 eggs hatched. In spite of thissmall number the analyses were carried out in an attemptto confirm Brody's generalization of the independenceof efficiency from incubation time and species.The l0 eggs used to estimate the combustion value of theostr ich egg had an averagelnmass(g)of  6,9991 t  0,1209and an average ln energy content (KJ) of 8 ,8776 t 0,1 178A linear regression analysis with egg mass as the in-dependent and energy content as the dependent variableyielded a slope (b) of 0,7601 and a ln intercept (a) of3 5577 with Sy. x and r as 0,078 I and 0 9802 respectively.The masses of the 2 hatched eggs were known and theirenergy content was estimated by linear regressionprocedures. The combusion values of the differentcomponents of the 2 hatched eggs are indicated inT a b l e  l .From Table I the average gross efficiency is:4618x  100 =  64 ,8%4618 + 2513and the average nergy loss is:25 r3994 6 1 8  +  2 5  l 3x  1 0 0  =  3 5  2 %Table ICombustion volues of the 2 hatched eggsEgg I EeE 2 MeanMass of unhatched eggEstimated combustion value of eggCombustion value of hatched eggCombustion value of unused material6,563KJlg 6,563KJlg 6,563KJlgl 0 l 8  g6682KJ( r0o%)4399KJ( 6 5 , 8 % )2IgKJ( 3  3 % )1308 g8585KJ( t 0 0 % )4838KJ( s6 l%)784KJ( 9 , 1 % )2962KJ(34 ,5%)1 1 6 3  g7633KJ( roo%)46 l8KJ( 6 0 , 5 % )5O2KJ(6 ,6%)25 l3KJ( 3 2 9 % )a 321KJ le 3 ,699KJ le + 010 KJ/e0,215KJ/g 0,60OKJ/g 0,408KJ/gEnergy lost during incubation (subtraction) 2064KJ(3og%\Z 928KJ le 2,265KJ lg 2,147 KI lsThis estimate of 64,8 percent for prenatal efficiency intake can thus be estimated using this efficiency figure.is in good agreement with Brody's preferred values,and An estimate of prenatal energy intake, even if it is nothis conclusion that the size of an egg and the incubation very accurate, is preferred to one of zero, as the contri-time have no influence on the prenatal efficiency of bution of prenatal intake to the cumulative intakeenergy utilization. during a growth experiment decreases rapidly withtime, so that errors of moderate size sooll becomeIt seems therefore that an approximate value of 60 -65 relatively small and unimportant. For exarnple, a valuepercent, or for convenience 213, for prenatal efficiency of 85 percent instead of 65 percent in the rat,induced amay be acceptable for all animals. The prenatal energy difference of only 3 percent at weaning(21days of age).ReferencesBRODY, S., 1945 . Bioenergetics and growth. New York: Reinhold.KEMM, E.H., 1980. The influence of dietary energy concentration on the growth efficiency of ad libitam fed pigs.Energt Metabolism hoc. 8th Energ,t Symp., Cambidge 1979. Butterworths, London.KIELANOWSKI, J., 1965. Estimates of the energy cost of protein deposition in growing animals. Proc. 3rd EnergtMetab. , Troon I964. htbl. Eur. Assoc. Anim. Prod I I , 13.MEISSNER, H H., 1977. An evaluation of the Roux mathematical model for the functional description of growth.Ph.D. thesis. University of Port Elizabeth, Republic of South Africa.MEISSNER, FIH.,  ROLIX,CZ. & HOFMEYR, H.S.,  1975. Voluntary feed intake, body composi t ion and ef f ic iency inthe sheep: Breed and sex differences.Agroanimalio 7, 105.PARKS, J.R., 1970. Growth curves and the physiology of growth. I Animals.Amer. J. Physiol. 219,833.PARKS, J.R.,1972. The physiology of growth. Animals as input output devices. Proc. International Summer School onthe computer and Res, in Nutr. and vet. Med., 37 - 51. Denmark ElsinorePARKS, J.R., 1973. A stochastic model for animal growth. J. Theor. Biol. 42,505.PARKS, J .R., 197 5a. The animal growth phase plane. J. Theor. Biol. 55 ,37 | .PARKS. J.R., 1975b. A theory of animal weight response to controlled feeding.l. Theor. Biol.55,38l.ROUX, C 2.,I976. A model for the functional description of growth and production. Agroanimalia 8,83.SC!IOLTZ, M-l\ '1. & ROUX,CZ., 1980. The allometric-autoregressive model in genetic studies: Different physiologicalphases in the rat .J.  Anim. Sct.  I  1,27.r00

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The likely efficiency of prenatal energy utilization

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The likely efficiency of prenatal energy utilization

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