Appendix 1 provides a preliminary insight to phenotypic characterization of the local scavenging chickens of Tanzania.
Local scavenging chickens in Tanzania have always been considered as a distinct breed of chicken different from the known commercial hybrids such as commercial layer or broiler chickens This study has provided preliminary facts, which reveal that the local chicken population is a pool of heterogeneous individuals, which can be separated by geographical locations henceforth, referred to as ecotypes. Differences in adult body weight and size, comb type, body length, shank length and egg weight were shown to exist in scavenging local chickens ecotypes studied. The results are in agreement with the findings by other authors who have reported differences in phenotypic characters of the scavenging local chickens. In this study five types of scavenging local chickens were identified namely, Mbeya, Morogoro-medium, Morogoro-short, Mwanza and Tabora.
Immunocompetence has been used extensively as an indicator trait in disease resistance of chickens. In assessing the immunocompetence of the Tanzania scavenging local chicken ecotypes, using both the humoral and the cellular immune responses, it was found that differences were as pronounced within ecotypes (where some individuals had a high response while others had a lower response) just as between ecotypes. Results from this investigation which are presented in Appendix 2, suggest the existence of high responder and low responder chickens in all ecotypes with reference to the multideterminant antigen system - Sheep erythrocytes.
Appendix 3 presents an investigation of the susceptibility of the Tanzania scavenging local chicken ecotypes to experimental infection with Newcastle disease virus and Salmonella gallinarum. Results from Newcastle disease experiment revealed that all chickens included in the experiment were susceptible to the virus this is in agreement with the current view that Newcastle disease is the number one killer in the local chicken sector. However, in the S. gallinarum experiment chickens from the Mwanza ecotype survived the challenge, suggesting a possible natural resistance to this pathogen. This is the first report on resistance to experimental infection with S. gallinarum in scavenging local chickens in Tanzania. Other reports on resistance to S. gallinarum were in some lines of White Leghorn chickens
The chicken MHC or the B-Complex has been associated with natural disease resistance and production traits Serological method of typing is a useful and simple technique employing specific alloantisera (B-F and B-G). In Appendix 4 results of a preliminary serological MHC typing of the scavenging local chicken ecotypes are presented. The results from this experiment suggest that the scavenging local chicken ecotypes in Tanzania may snare some cell membrane antigens (B-G and B-F) with some of the standard B haplotypes of International reference populations. Inability of some of the standard alloantisera to type the local chickens was interpreted as a testimony of a possible existence in the local chicken population of B haplotypes outside the standard repertoire.
The present study has revealed phenotypic differences between scavenging local chicken ecotypes. Furthermore an ecotype from Mwanza has indicated a possible resistance to S. gallinarum, and a possibility of the presence of B-haplotypes of known potency in disease resistance and productivity has been revealed. Taking these three major findings and that of differences in immunocompetence between individual chickens within ecotypes, it is evident that more work is required to expound the role of each of these findings in relation to the survival of the scavenging local chickens as well as their productivity. |
