|dc.description.abstract||The broad objective of the study was to determine the effect of provitamin A biofortified maize (PABM) inclusion, sex and age on growth performance, carcass traits, blood composition, meat quality, vitamin A content, nutritional value and consumers’ acceptability of Ovambo chickens. The aim of the study was to evaluate the potential of delivering provitamin A in yellow-orange biofortified maize to vitamin A deficient -vulnerable population groups who prefer provitamin A-devoid white maize. This was achieved through feeding indigenous chickens on the PABM with the expectation that the chicken carcass would have increased concentrations of vitamin A. A total of 102 Ovambo chickens, indigenous to southern Africa, were reared and fed two dietary treatments; the control, white maize (WM) and a PABM-based diet for nine weeks. There was no significant effect of diet on the average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR). Male birds had higher (P<0.05) ADFI and ADG than the female birds. There was also an interaction of diet, age and sex on ADG and ADFI.
Male birds fed on the PABM had higher (P<0.05) ADFI at 15 weeks and 21 weeks of age than the WM fed male birds. Male birds had higher (P<0.05) ADG than the female birds at 15- 17 weeks of age. Male birds fed on the PABM diet had a significantly higher ADG at 16 weeks of age. The PABM fed female birds had a higher ADG than the WM fed females at all weeks except 21 weeks of age and was significantly higher at 19 weeks of age. The PABM fed female birds had significantly lower FCR at 20 weeks than the WM fed female birds. The male birds had higher (P<0.05) FCR at 21 weeks than the female birds.
The PABM diet had a significant effect on the dressed carcass (DC) and leg weight of the birds. Female birds had higher (P<0.05) relative breast and back weights, whilst the male birds had higher body weights (BW) and leg weights (P<0.05). The DC, leg (thigh and drumstick) and back relative weight of the birds significantly increased as the ages at slaughter increased. The PABM fed birds had a significantly higher relative weight of gizzard and liver than the WM fed birds (P<0.05). The female birds had higher gizzard and liver weights than the male birds (P<0.05). The gizzard and liver weights of the birds decreased with increasing age. The relative heart weight of the male birds increased with age and was higher than that of the female birds (P<0.05).
The PABM diet increased the packed cell volume (PCV) of the birds and the leucocytes (WBC) of the PABM fed female birds were within the normal range but significantly higher than the WM fed female birds. The mean corpuscular haemoglobin (MCH) of females fed on PABM was lower than that of the PABM fed male birds and the WM fed female birds. All the mean values of the haematological parameters were within the normal range regardless of the age, sex and diet of the birds. Age had an effect (P<0.05) on alanine transaminase (ALT), total protein (TP), GLOB, triglycerides (TRI) and uric acid (UA). The sex of the birds significantly influenced the TP, GLOB, ALB, CREAT and TRI concentrations. The interaction of diet and age had a significant influence on the ALP, ALT and GLOB concentrations. The PABM diet, sex and age of the birds or their interactions had no significant overall effect on the pH, drip loss (%), cooking loss (%) and shear force of meat (P>0.05). The meat and skin of PABM fed chickens had higher Hunter a* (redness) and b* (yellowness) and lower Hunter L* (lightness) values. The skin of the female birds had higher Hunter L* (lightness) values than that of the males (P<0.05). As the age of the birds increased, the skin of the WM fed females became lighter (Hunter L* values increased), whilst the intensity of the yellow colour of the skin of the PABM fed male birds increased (a* values increased) (P<0.05). The PABM improved the vitamin A concentration in the Ovambo breast meat. The WM fed chicken meat had an average of 40mcg/100g while the PABM diet increased the vitamin A concentration to 55mcg/100g. Sex and the interaction of diet and sex did not significantly affect the vitamin A concentration in the Ovambo meat. The PABM and sex had no significant effect on the moisture, crude protein and fat content of the meat. The ash content of the meat of the female birds was higher (P<0.05) than that of the male birds. The sex of the bird and diet had no effect on the mineral composition of the muscle. The interaction of sex and PABM diet impacted on the copper concentration of the Ovambo chicken meat. The sensory characteristics of the meat of the PABM and WM fed chickens were not significantly different. Age and gender of the consumers and their interactions had no significant effect on the acceptability of all the sensory attributes of the Ovambo chicken meat evaluated. The findings of this study concluded that indigenous chickens fed PABM can be a tool for curbing VAD and improving the meat quality of indigenous chickens in southern Africa regions.||en_US