In a 2 x 2 factorial design, attainment of puberty in 32 Black Indigenous (BI) and 60 SA Landrace (SAL) gilts was studied under the effects of two treatment diets fed individually ad libitum. Treatment 1 contained 160 g CP and 13.6 MJ DE/kg DM, and Treatment 2, a 25% dilute of Treatment 1 using wood shavings, contained 120 g CP and 10.2 MJ DE/kg DM. Target weights set for BI gilts were from 10 to 50 kg and for SAL, 15 to 120 kg. A sample was slaughtered at each target weight. Reproductive organs were removed, measured and the number, size and physiological state of follicles recorded. Carcasses were deboned and the soft tissue analysed for moisture, protein and fat content. Treatments affected growth significantly. Cumulative mass (lnkg) was regressed against cumulative ME intake (lnME) with b the allometric coefficient in a linear autoregressive model. A change in b indicated a change or breakpoint of physiological development. Puberty was taken to coincide with the breakpoint. Age and weight at puberty differed by treatment for each genotype. Estimated live weight fat (percentage) and carcass fat (percentage) at these ages show a close range between genotypes and treatment diets.