| The experiment was conducted on Vanaraja chicken breeder flock maintained in three separate experimental pens in which two (T 1 and T 2 ) were treatment pens and T 0 was control pen with 1:8 male to female mating ratio and total birds ranging from 88 to 90 in each pen. At the end of 48 th , 49 th , 52 nd and 55 th Weeks Of Age (WOA), 150 eggs were randomly selected from each pen and a sum of 450 eggs from the three pens, were set in incubator for incubation. At the end of 48 th week for

more »

... piking 3 roosters from experimental pen T 1 were transferred to T 2 and another 3 roosters from pen T 2 were transferred to T 1 . Increase in fertility rates were observed at 52 and 55 WOA after the initial reduction at 49 WOA after interspiking in all the groups. However more increase was observed in the interspiked T 1 and T 2 groups. The hatchability values on Total Eggs Set (TES) basis at 52 and 55 WOA of interspiked groups were found higher than those of the non interspiked control group of birds. There was gradual increase in TES hatchability after interspiking from 49 to 55 WOA in T 1 and T 2 groups than those before interspiking. However, in all the age groups there were no significant differences in TES hatchability rates among the treatments. While evaluating the hatchability rate on Fertile Eggs (FES) basis in all the age groups, no significant differences were found among the treatments. An increase in FES hatchability rate of all the treatment groups has been found as the age advances. However, more increase was observed in interspiked groups (T 1 and T 2 ) compared with control T 0 group. The findings indicate that interspiking of Vanaraja roosters can be advantageous especially in flocks showing lower fertility rates.