An evaluation of ratios as a measure of carcass traits using mature indigenous chickens in Limpopo Province of South Africa
Live weight and weight of body parts of 60 mature indigenous chickens were collected to investigate whether the use of ratios in poultry science may cause misinterpretation of data and misleading conclusions. Three villages from Mukula Tribal land in Thulamela municipality from Vhembe District in Limpopo Province of South Africa were identified for the purpose of this study. Five mature chickens were bought from each village, weighed, killed, dressed and cut to get the body parts using the standard procedures. This was done across the four distinct seasons from March 2005 to March 2006. The data was collected using a weighing scale with variables of interest being the sex, season and village. Summary statistics were computed and data was analyzed in two separate ways using the Statistical Analysis Software Packages as follows: Firstly each individual body part was expressed as ratio of body weight and data analyzed using a simple analysis of variance (ANOVA) procedure. Secondly, live body weight was used a covariate in the analysis of other body parts using the ANCOVA procedures. Ratios suggested differences gizzard, liver, head and feet and body length due to sex and in gizzard, liver and body length due to village which were not apparent with ANCOVA. The results from this study suggested that ratios did not remove the variation due to differences in sex and village and may lead us to wrong conclusions. From this study, one can draw conclusions that use of ANCOVA gives us the exceptional method for interpreting the data correctly.
Keywords: Ratios, ANCOVA, live weight, body parts