Poultry provide affordable animal protein products compared to other animal products in agricultural industry. The demand of organic food by world health organisation and call for discard of conventional laying cage production method led to this research study. The aim of the study was to determine how (4 x 4) full diallel crossbreeding of the Potchefstroom Koekoek (PK), Naked neck (NN), Lohmann Brown (LB) and White Leghorn (WL) had an effect on production performance, egg parameters, genetic and phenotypic characteristics of F1 crossbreed offspring. The study was conducted at the Agricultural Research Council (ARC), Livestock Production Improvement at the Irene Campus, which is situated about 25 km south of Pretoria. The (4 x 4) full diallel crossbreeding design used on four chicken breeds to produce four pure breeds, six crossbreeds and six reciprocal crosses. The total number of 352 chickens with16 treatments (2 cocks and 20 hens) used in phase 1 and 384 chickens 16 F1-treatments (3 cocks + 21 hens) used in phase 2. Data was analysed by full factorial analysis of variance (ANOVA), General Linear Model procedures and Scheffe post-hoc for multiple comparison of the means of different variable data. The outcome had shown that crossbreeding had an effect on the production performance, genetic and phenotypic characteristics. The performed F1 crossbreeds emerge from crossbreeding between the local dual-purpose PK and commercial LB chicken breeds. PKLB dominated on growth and production performance traits compared to other crossbreeds. All set null hypothesis differ significantly at (p < 0.05), the outcome of all five hypothesis of this study were rejected. In conclusion PKLB was the best performing F1 crossbreed, based on its best performance on growth, FCR, cost of rearing, productive, high quality safe eggshell, economic efficiency and consumer preference (brown eggshell and yolk colour). / Dikgogo di neelana ka dikumo tsa poroteine ya diphologolo go tshwantshanngwa le dikumo tsa diphologolo tse dingwe mo intasetering ya temo. Tlhokego ya dijo tse di bolang mo mekgatlhong ya boitekanelo ya lefatshe le pitso ya go latlha mekgwa ya kumo ya dikgetshe tsa go beela tsa tlwaelo di ne tsa isa kwa thutong ya patlisiso eno. Maikaelelo a thuto eno ke go tlhomamisa gore tsadiso ya kgabaganyo ya dilo tse pedi kgotsa go feta go tshwantshanya kgolagano ya mofuta wa dijene le tikologo tse di tletseng tsa (4 x 4) tsa Potchefstroom Koekoek (PK), Naked Neck (NN), Lohmann Brown (LB) le White Leghorn (WL) di na le ponalo mo tiragatsong ya kumo, diparametera tsa mae, le dijene le diponagalo tsa kgolagano ya mofuta wa dijene le tikologo tsa ditsadiso tsa kgabaganyo tsa ngwana wa F1. Thuto e ne ya diragadiwa kwa Agricultural Research Council (ARC) le Tokafatso ya Kumo ya Diruiwa kwa khempaseng ya Irene, e e agilweng bokana ka 25 km jwa borwa jwa Pretoria. Ditsadiso tsa kgabaganyo tsa dilo tse pedi kgotsa go feta go tshwantshanya kgolagano ya mofuta wa dijene le tikologo tse di tletseng tsa (4 x 4) di ne tsa dirisiwa mo mefuteng ya ditsadiso tsa dikgogo go ntsha mefuta ya ditsadiso e e tletseng e mene, ditsadiso tsa kgabaganyo tse thataro le dikgabaganyo tse di tshwanang tse thataro. Palo e e tletseng ya dikgogo tse di 352 ka ditiragatso di le 16 (mekoko e le 2 le dithole di le 20) di ne tsa dirisiwa mo letlhakoreng la 1 le dikgogo di le 384 ka ditiragatso tsa F1 di le 16 (mekoko e le 3 + dithole di le 21) di ne tsa dirisiwa mo letlhakoreng la 2. Data e ne ya tshetshereganngwa ka tshetshereganyo ya dintlha tse di tletseng tsa pharologantsho (ANOVA), dikgato tsa General Linear Model le tshwantshanyo ya bontsintsi ya morago (ANOVA), dikgato tsa General Linear Model le tshwantshanyo ya bontsintsi ya morago ga tiragalo ya Scheffe ka mekgwa ya data ya pharologantsho e e farologaneng. Ditlamorago di ne tsa bontsha gore ditsadiso tsa kgabaganyo di na le ponalo mo tiragatsong ya kumo, ga mmogo le diponagalo tsa dijene le setlhopha sa kgolagano ya mofuta wa dijene le tikologo. Go ne ga diriswa mefuta ya ditsadiso tsa kgabaganyo ya F1 tse di tlhagelelang go tswa mo ditsadisong tsa kgabaganyo magareng ga mefuta ya ditsadiso tsa dikgogo tsa PK tsa lebaka la gabedi la selegae le LB ya kgwebo. PKLB e ne ya fekeetsa metlhala ya tiragatso ya kgolo le kumo go tshwantshanngwa le mefuta ya ditsadiso tsa kgabaganyo tse dingwe. Setlhopha sotlhe sa dikakanyo tsa lefela se x farologana mo go bonagalang ka (p < 0.05) le ditlamorago tsa dikakanyo tse tlhano tse tsotlhe tsa thuto eno di ne tsa kganediwa. Kwa bokhutlong, PKLB e ne ya nna mofuta wa ditsadiso tsa F1 o o diragatsang go gaisa, go ikaegilwe ka tiragatso mabapi le kgolo, FCR, tshenyegelo ya go tsadisa, kumo, boleng jo bo kwa godimo jwa dikgapetla tsa mae tse di babalesegileng, bokgoni jwa ikonomi le boikgethelo jwa modirisi (dikgapetla tsa mae tse di tshetlha le mmala wa tlhae). / Agriculture and  Animal Health / Ph. D. (Agriculture)

MSCAGR (Plant Production) / Department of Plant Production / Smallholder farmers in Sub-Saharan Africa still obtain low grain yields in maize largely due to low soil fertility. The soils are inherently low in nitrogen (N) that is required for the proper development of the maize plant. Currently there are no commercial cultivars for low N tolerance locally. The combining ability approach can be used as a tool for breeding desirable cultivars. In order to improve grain yield in maize, it is important to consider ear prolificacy which is a major yield component. Therefore this study was designed to estimate combining ability in maize. Exotic germplasm from the International Maize and Wheat Improvement Center and the Institute of Tropical Agriculture as well as the local germplasm from the Agricultural Research Council was used in the study to generate crosses. One hundred and two crosses were evaluated together with a standard commercial check under low N and optimum N conditions. The specific objectives of the study were to determine general and specific combining ability for prolificacy among local and exotic inbred lines and evaluate the response of prolific hybrids to low N conditions. The hybrids were planted in the 2014/2015 summer season under irrigation in Potchefstroom, Cedara and Taung in field plots consisting of 0.75m x 0.25m spacing in a 0.1 alpha lattice design replicated twice. Data for agronomic attributes were recorded and subjected to analysis of variance using SAS version 9.1.3. Genetic correlations were analyzed using the Principal Components Analysis and factor analysis based on the correlation analysis and major traits. The results showed variation in agronomic performance among the inbred lines and their F1 hybrids. Inbred lines including TZEI63, T1162W, L15 and L17 showed positive GCA estimates for ear prolificacy at the different locations. Specific combining ability for prolific hybrids was positive at all locations and environments. The GCA:SCA ratio was close to unity; indicating that the number of ears per plant showed highly significant (P<0.01) correlation with grain yield. The hybrids showed ear prolificacy under the low N conditions. This trait can be used effectively in stress tolerance maize breeding programmes. / NRF