Comparative developmental trajectory of four strains of chicken embryo during incubation and their post-hatch growth
This study evaluated egg traits, embryonic growth, and early growth rate in four strains of chicken. A total of 1200 hatching eggs, 300 each from four strains of chicken were used for this study. The strains included Nigerian indigenous chicken (NIC), Arbor acre, Hubbard, and Marshall broiler strains. Embryonic weights, yolk and albumen utilization were monitored throughout the incubation period. The chicks were randomly distributed into four rearing pens for a 28-day assessment of growth rate. Blood samples were collected at hatch (day-old), week 1, 2, 3 and 4 posthatch for thyroxine (T4) level determination. This study showed that the embryos 4 percentage weight gains were similar in the NIC and the broiler strains at embryonic (ED) 18. There was no difference (P>0.05) in the rate of albumen utilization among the strains. At hatching, there was no difference ((P>0.05) in the metabolic rate among the strains of chicken as shown by the levels of plasma T until later in the 4 growth phase. The day-old chick weight and the weights in subsequent weeks posthatch were smaller in the NIC than the broiler strains possibly as a result of low hatching weight and growth rate of the NIC in the first two weeks post-hatch. The early growth difference could not be explained by physiological parameters such as T4 . However, the differences in post-hatch physiological and metabolic parameters 4 may be due partly to genetic differences. It was concluded that embryonic development in the broiler strain was not superior to that of the NIC.
Key words: Growth rate, metabolic rate, albumen utilization