Du Preez, J.J.

Gevers, H.O.

Gous, R.M.

Quicke, G.V.

English

AJOL - African Journals Online

UTILIZATION OF PROTEIN FROM OPAQUE -2 MAIZE BYCHICKEN AND RATProewe met kuikens en rotte toon dat die netto benutting van protem (NPB) van Opaque -2 (0) mielies betekenisvol hoer is as dieNPB waardes van normale (N) mielies. Altesaam sewe mielie varieteite is aan die toetse onderwerp en die drie varieteite wat die 0 geen besit,het die drie hoogste posisies van NPB waardes beklee. In die kuikenproewe is mieliemeel van heel pitte van die N varieteit met 0,013 %I-triptofaan en 0,04% l-lisien aangevul en hierdie rantsoen was nie betekenisvol swakker as twee van die 0 varieteite nie. 'n KommersieleN tipe geelmieliemeel wat in die proef ook met bogemelde pelle van dieselfde amino sure aangevul is het ook nie betekenisvol swakker NPBwaardes as twee van die 0 varieteite getoon nie, dog met verdubbeling na die aanvulling van beide amino sure het die geelmieliemeel niebetekenisvol van die beste 0 varieteit verskil nie.Opaque -2 maize gave significantly better nett protein utilisation (NPU) values than normal maize varieties in trials performed withrats and chickens. Altogether seven varieties of maize were tested of which three carried the opaque -2 gene and these proved to rank first,second and third in NPU values. In the chicken trial normal white maize supplemented with 0,013% I-tryptophan and 0,04 %l-lysine was notsignificantly different to two of the Opaque -2 maize samples. A commercial normal yellow maize fortified with similar levels of theseamino acids held a similar position as the fortified N variety, however, supplemented with higher levels of these amino acids (double the formerlevels), yellow maize was not significantly different to the top Opaque -2 maize variety in the trial.The Opaque -2 gene causes a marked alteration ofthe amino acid composition of maize endosperm protein.Mertz, Veron, Bates & Nelson (1965) were the fust todemonstrate that the nutritional value of Opaque -2maize is superior to normal maize in rat feeding trials. Sub-sequently Opaque -2 maize was shown to have highernutritional value than normal maize for pigs (Cromwell,Pickett and Beeson, 1967), for the chicken (Cromwell,Rogier, Featherstone and Pickett, 1967; Cromwell, Rogier,Featherstone and Cline, 1968) and for laying hens (Fonseca,Featherstone, Rogier and Cline, 1970).This gene was incorporated into South African lines(Gevers, 1970) and preliminary biological tests of twoopaque -2 composites showed the whole grain to be de-cidedly superior in tenm of rat growth and nett proteinutilization to the grain of their normal counterparts (Quicke& Gevers, 1972).The subsequent production, in larger quantities, offresh strains of locally-developed whole·kerneUed Opaque-2 maize prompted further biological evaluation of thistype of maize. This paper reports the nett protein utiliza·tion of the new material as determined in preliminary ex-periments with rats and in more extensive tests with youngchickens. Whole kernel meal of two opaque -2 top-crosshybrids and an Opaque -2 variety were compared withwhole·kernel meals of 3 white strains, and a commercialyellow mealie meal. The effect of additions of lysine andtryptophan to the meal of one of the normal white varietiesand to the yellow maize meal was also studied.All maize meal were ground to pass a 1 mm sieveand, with the exception of the commercial yellow mealiemeal, were prepared as whole-grainmeals.Rat diets Maize diets, made up to contain approximately9% protein and N·free diet were prepared as previouslydescribed (Quicke & Gevers, 1972).Chicken diets The general composition of the chicken dietswhich contained 92,5% maize meal is given in Table l.MaizemealStarchVitamin mixture •Mineral mixture ••KH2P04CaHP04CaC03Sunflower oil92,50O,QI0,441,010,601,441,003,00100,00mgper kg ration: choline chloride 2000; niacin 50; thiamineHCL 25; riboflavin 16; Ca pantothenate 20; pyridoxin 6;folic acid4;biotinO,6;B12 0,02;menadion 5; vitamin C 250;Lu. per kg ration: A 5000; D 800; E 12.gper kg ration; NaCI6;MgS04 3;Fe Citrate 0,5jMnS04.H200,35; ZnC03 0,2; CuS04.5H20 0,3; KI O,QI;Na2Mo04.H200,01; Na2Se04 0,002.• Present address: Plant Breeding Section, Natal Region, Department AgricQlturalTechnical Services,Pieterrnantzburg.97Table 2Description of individual diets. All maize meals comprised 92.5%of diet as shown in Table 1(T = top cross hybrid; V = variety)Code Type maize meal Amino acid supplement N-content of Lysine contentadded mg per 100 g diet diet of dietgJ100 g gJI00 gL-tryptophan • L-lysine**MPF-5 Normal white T 1,58 0,281MPF-6 Opaque -2 white T 1,42 0,362MPF-7 Opaque -2 white T 1,39 0,403MPF-8 Normal white T (SA 15) 1,54 0,304MPF-9 Opaque -2 white V 1,50 0,391MPF-10 Normal white V 1,47 0,246MPF-10-TILI 13,84 51,79 1,47 0,288MPF-I0- T2L2 27,72 103,6 1,49 0,332YM Commercial yellow maize meal 1,46 0,228YM-TILI 13,84 51,79 1,42YM-TIL2 13,84 103,6 1,41YM-T2Ll " 27,72 51,79 1,43YM-T2L2 27,72 103,6 1,44 0,320Additions of 13,84 and 27,72 mg/l00 g correspond to 0,013 and 0,026%of completedietAdditions of 51,79 and 103,6 mg/IOOg correspond to 0,04 and 0,08%of complete dietThe N-free diet was prepared in the same way except thatmaize meal was replaced by starch givinga total starch con·tent of 92,51 per cent. Table 2 provides a brief descriptionof the maize samples tested, the amino acid supplementsand the N- and lysine content of the complete diets.Diets containing whole kernel meals MPF-5 to 9 anda corresponding N-free diet were each fed to a separategroup of 4 albino rats in a single8-day trial. Weightgainsanddaily feed intakes were recorded and the data used toevaluate protein efficiency ratio (PER) and net proteinutilization (NPU) by the method of Bender & Doell (1957).Cornish Game x Plymouth Rock broiler chickenswere raised to one week of age on a chicken starter diet.After discarding very heavy and very light birds, the re-maining280 chickens were split up into four weight classes.Each of the 13 experimental diets (Table 2) and the N-freecontrol diet were fed in a randomised block design to4 groups of 5 chickens, each of these groups being selectedto represent one of the 4 weight classes, thus affording 4replications per treatment. NPU values were determinedin a 8 day feeding trial according to the method of Bender& Doell (1957) as recommended for chickens by de Muele-naere, Quicke and Wessels (1960), the N-content of eachcarcass being estimated from the moisture content usingthe regression equation of Wessels& Bundock (1968). Theweight gains were also used to evaluate nett protein ratio(NPR) as described by Render & Doell (1957).Nitrogen and protein (N x 6.25) were determined bythe Kjeldahl prosedure and lysine was determined using aBeckman 120B analyser as described by Quicke & Gevers(1972).The results of the rat trial (Table 3) clearly indicatethe superiority of Opaque -2 white maizeover normal whitemaize. The PER values of opaque kernels compared wellwith those (1,73 and 2,32) reported previously (Quicke &Gevers, 1972) as do the NPR-valuesalthough the latter areslightly higher for the opaque kernels than the earliervalues (3,40 and 3,88). The PER values have been used insimilar comparisons by a number of authors, but aspointed out by Quicke & Gevers, 1972, the poor intakeProtein efficiency ratio (PER) and nett protein ratio (NPR)values of opaque -2 (0) and normal (N) white kernelledmaize (whole grain) for growingratsMaize sample PER NPR Estimate NPU*MPF-5 (N) n.v.** 2,89 46,2MPF-6 (0) 1,78 4,38 70,1MPF -7 (0) 1,60 4,25 68,0MPF-8 (N) n.v. 2,67 42,7MPF-9 (0) 1,78 4,18 66,8*** n.v.Estimated NPU = NPR x 16Negative values as rats did not gain weighton normal maize diets is a distinct disadvantage and mayresult in an under evaluation of normal relative to Opaque-2 maize. This problem is emphasized in the present studyin which the performance of the rats on the normal maizewas so poor that it was not possible to evaluate the PER.Notwithstanding the shortcoming of the Bender &Doell procedure NPR values offer a useful criterion forcomparing the nutritive value of normal and opaque -2maize. Following the suggestion of Bender & Doell (1957)NPU's were estimated from the NPR values by multi-plying by the factor 16. These calculated values agree wellwith the NPU's of Opaque -2 and normal maize obtainedby the carcass analysis procedure in the previous study(Quicke & Gevers, 1972).The results of this trial are presented in Table 4, eachvalue being the mean of 4 replications. The diets are arrangedin descending order according to their respective NPUNett protein utilization (NPU) and nett protein ratio (NPR)values for chicks. of opaque -2 and normal white kernelledmaize (whole grain) and a commercial yellow mealie mealwith and without lysine and tryptophan supplementation.Diets ranked according to NPU values. All values aremeans of 4 replicatesDiet code RankingNPU NPR1 12 33 54 25 46 77 68 119 810 9II 1212 1313 10MPF-6MPF-7MPF-9YM-T2L2YM-TIL2MPF-IO-TI LlYM-TILIMPF-8YM-T2LlMPF-IO- T2L2MPF-lOMPF-5YM74,59 (a)*70,62 (ab)68,69 (abc)68,63 (abed)66,98 (bcde)64,67 (bcdef)64,26 (bcdef)63,79 (cdef)62,02 (ef)61,71 (ef)60,89 (ef)59,I8(f)58,75 (f)4,944,764,634,794,744,354,404,004,284,223,933,774,07Averages not followed by the same alphabetic charac-ter differ significantly from one another (P.:::0,05).values. MPF-6 a top-cross opaque -2 white hybrid had thehighest mean NPU value while the commercial yellow maizemeal had the lowest. Direct comparison of the white maizemeals with the yellow maize meal is not strictly valid asthe former include the germ with its more favourable aminoacid balance, whereas the germ is excluded from the com-mercial meal. However, the three normal white maizemeals (MPF -5,8 and 10) serve as valid controls and theNPU values of the Opaque -2 samples are significantlyhigher (P~0,05) than those of these normal whole-kernelcontrols.The results reported here are in agreement withfindings of other workers such as Cromwell et al. (J 967),who applied growth methods to show that the protein ofOpaque -2 maize is of higher nutritional value thannormal maize for chickens. The N.P.U. method, which is amodified nitrogen balance method and a test of greatersensitivity than growth studies, has to our knowledge, notbeen applied hitherto in nutritional comparisons of Opaque-2 and normal maize with chickens although it has beenused, with similar results, in tests on rats (Quicke & Gevers,1972). The present results also support the work ofYoung, Osalp, Cholakos and Scrimshaw (1971 ), who assessedthe NPU value of Opaque -2 maize with human subjects.They concluded that, for human nutrition, Opaque -2maize protein is comparable to some proteins from animalorigin.The growth data obtained with the chicks in thisexperiment were also used to estimate NPR values whichare included in Table 4. These values are somewhat higherthan the corresponding values obtained in the rat trial, thistrend being noticeably more marked for the normal maize(MPF -5 and MPF -8) than for the three Opaque -2 meals(MPF -6,7 and 9). It is noteworthy however that the orderof ranking of these 5 meals is exactly the same irrespectiveof the criterion used, i.e. rat or chick NPR values, estimatedrat NPU values, or chick NPU values by the carcass analysisprocedure. Although the data are limited, there is a strongindication that growing chicks make better use of the pro-tein of normal maize than do rats, so that differences in thenutritive value of Opaque -2 and normal maize are lessmarked, although still significant, when the chick is used astest animal.The nutritional superiority of the Opaque -2 samplesis largely attributable to the beneficial effect of the higherlysine and tryptophan levels in these samples. This is clearlysubstantiated by the results obtained with the diets in whichthe amino acids were added to yellow maize meal and tothe whole-kernel normal white variety (MPF -10- T 1- L I ).The poor response to the addition of higher levels of theseamino acids to this meal (diet MPF-IO-T2-L2) is sur-prising however, and not readily explained. This diet con-tained 0.331 per cent lysine by analysis which is close tothe lysine level in MPF-6 and higher than that of the mostheavily supplemented yellow maize meal (YM- T2L2). Inthe absence of further data no definite conclusion can bereached but it seems that in some instances the beneficialeffects of amino acid supplementation of maize meals maybe subject to interference by complicating factors.That part of the experiment in which the yellowmaize meal was supplemented with two levels of lysine andtryptophan constituted a 2 x 2 factorial design with eachtreatment replicated four times. These results could there-fore be subjected to further statistical analysis as sum-marized in Table 5. This analysis shows that while adoubling of the level of lysine supplementation from 0,04to 0,08 (corresponding respectively to 2,8% and 5,6% ofthe dietary N) resulted in an improvement of nettprotein utilization no such response was effected by in-creasing the level of tryptophan supplementation from0,013 to 0,026% (corresponding respectively to 0,918%and 1,81%of the dietary N). It appears therefore that infuture work of the amino acid supplementation of maizediets tryptophan additions amounting to more than 0,013%need not be considered although additional tryptophanmay be required if lysine levels are increased above thelevels used here.An important feature of the data obtained in thechick trial was the demonstration of a highly significant(P.$.0,01) effect of the initial mass of the chicks on NPUvalues, as revealed in the analysis of variance of the ran·domised block design. This fmding raises the possibilitythat the· breed of chicken used may influence the resultingNPU values especially when breeds differ as widely as themodem specialized breeds as for example broilers andlayers. This aspect requires further investigation.The shortcomings of the methods used in these stu-dies are well recognised as is the difficulty associated withthe assessment of protein quality of foods with such a lowprotein content. These difficulties notwithstanding, thethree Opaque maize samples tested in this study were clear-ly superior to the normal maize meals investigated and thesefmdings are in line with the results of most other workersin the field. It may be concluded therefore that Opaque -2maize can make a useful contribution to the now acuteproblem of protein supplies for animal feeding. This contri-bution will be all the more valuable if the incorporation ofthe Opaque -2 gene goes hand-in-hand with the develop-ment of lines which also have an increased protein content.Effect of higher levels of lysine and tryptophan supplementation on the NPU value of yellow maize meal. Each value is a meanof 4 replicates, each replicate consisting of 5 chickensL-lysine0,04% 0,08% MeansL-tryptophan 0,013% 64,2599 66,9749 65,61740,026% 62,0224 68,6299 65,3262Means 63,1412 67,8024 65,4718Standard errorFor a mean in the body of the tableFor a marginal meanLeast significantdifference1,95701,38384,42693,13036,36054,4975BENDER, A.E. and DOELL, BR., 1957. Biologicalevaluation of protein: a new aspect. Br. J. Nutr. 11, 140.CROMWELL,G.L., ROGLER, J.C., FEAmERSTONE, W.R.and CLINE, T.R., 1968. A comparison of the nutritive value ofOpaque -2, Floury -2 and normal com for the chick-Poultry Sci. 47,840.CROMWELL,G.L., ROGLER, J.C., FEAmERSTONE, W.R. and PICKETT, R.A., 1967. Nutritional value of Opaque-2com for the chick. Poultry Sci. 46, 705.CROMWELL,G.L., PICKETT, R.A. and BEESON,W.M., 1967. Nutritional value of Opaque -2 com for swine. J. Anim.Sci. 26, 1325.DE MUELENAERE, H.J.H., QUICKE, G.V. & WESSELS, J.P.H., 1960. The applicability to chicks of the carcass analysismethod for the determination of Nett Protein Utilization. S. Afr. J. agric. Sci. 10, 113.FONSECA, J.B., FEAmERSTONE, W.R., ROGLER, J.C., and CLINE, T.R., 1970. A comparison of the nutritive value ofOpaque -2 and normal com for the Laying Hen. Poultry Sci. 49, 532.GEVERS, H.O., 1970. On the recovery of the high-lysine mutants Opaque -2 and Floury -2 in maize. Proc. IVth Congr.S. Afr. Gen. Soc., Pretoria.MERTZ, E.T., VERON, O.A., BATES, L.S. and NELSON, O.E., 1965. Growth of rats fed on Opaque -2 maize. Science,148, 1741.QUICKE, G.V. & GEVERS, H.O., 1972. Higher Lysine levels and improved protein quality of Opaque -2-maize. S. Afr. med.J. 46, 1579.WESSELS, J.P.H. and BUNDOCK, M.J., 1968. Application to chickens of the carcass analysis method for determination ofnet protein utilization. III. The effect of shorter test period, sex and breed upon the body water-nitrogen relationshipin the chicken. S. Afr. J. agr;c. Sci. 11, 531 .YOUNGH, V.R., OZALP, I., CHOLAKOS, B.V. and SCRIMSHAW, NS., 1971. Protein value of Colombian Opaque -2com for Young Adult Men. J. Nutr. 101, 1475.

Utilization of protein from opaque -2 Maize by chicken and rat

https://www.ajol.info/index.php/sajas/article/download/140283/130037

Utilization of protein from opaque -2 Maize by chicken and rat

Abstract

Similar works

Full text

Available Versions

AJOL - African Journals Online