Abstract:
The primary objective of this research was to study the effects of agro-ecological regions (as represented by the veld types in four different areas), sex, season of birth, the interaction between sex and season of birth as well as the interaction between veld type and season of birth on selected anthropometrical measurements (body dimension measurements). The correlations between these selected anthropometrical measurements were also investigated in this study. Data from four herds of Nguni cattle comprising of 416 animals (Loskop South, Fort Hare, Kroonstad and Warmbaths with 115, 106, 97, and 98 animals respectively) was analysed. Measurements were taken in different seasons at each area or location. Statistical analyses of the data were done using the general linear model (GLM) procedure of the Statistical Analysis System (SAS, 2002). The results of this study indicate that veld type, sex and the interaction between sex and veld type did not significantly (P < 0.05) affect the growth (selected anthropometrical measurements) of Nguni cattle. In all the four agro-ecological regions (veld type in the different regions), season of birth, the interaction between sex and season of birth (Sex*BS) and the interaction between season of birth and veld type (V*BS) showed a significant effect (P< 0.05) on selected body dimensions. Animals that were born during the winter and spring seasons were heavier (P<0.05, 333.37 kg and 336.95 kg respectively) than those born in summer (270.35 kg) and autumn (286.29 kg). The same can be said of other body dimensions (M, L, HW, HG, SH and HH), whereby the animals that were born during winter and spring seasons had higher values (P<0.05) than their counterparts born in summer and autumn. This tendency was also observed for SC although the difference was not statistically significant. In conclusion, the study suggested that season of birth, the interaction between sex and season of birth (Sex*BS) and the interaction between veldtype (agro-ecological region) and season of birth (V*BS) are important sources of variation in growth of beef cattle, with special reference to Nguni cattle. It is therefore recommended that season of birth and its interaction with both veld type and sex should be given considerable attention in any extensive beef production system (with special reference to the Nguni breed) employed in South Africa. Knowledge of the influence of agro-ecological factors on the growth of beef cattle is of great importance for measuring production capacity, designing and implementing strategies to alter the extensive beef production system and thus to increase the output to ensure a more sustainable economic advantage.
