Performance evaluation for juvenile-growth and immune-competence traits for chicken sub-populations undergoing recurrent inbreeding for 3 generations
SURYAKANT MISHRA, R. P. SHARMA, R. C. HAZARY
AND S. R. SHARMA
Project Directorate on Poultry, Rajendranagar, Hyderabad- 500 030
A study was conducted to evaluate 3 genetic sub-populations originating from a dual purpose pure-line (D.Red), which are undergoing recurrent inbreeding for 3 consecutive generations. These subpopulations were basically created from a common genetic base for infusing graded amount of cumulative-homozygosity where in: one group (NB) was continually reproduced under random-mating conditions, with adequate sire base; in the 2 nd group (FS), deliberate full sib mating was practiced with minimum of 10 sire families per generation and in the 3 rd group (HS): deliberate half-sib mating was practiced (with minimum 10 sire base). After the 3 rd inbreeding generation, when the cumulative inbreeding co-efficients for these groups (as per expected gain per generation) stood at: NB with 0.0%, FS with 50.0% and HS with 30.0% levels, the progeny were evaluated for juvenile growth traits and immune-competence parameters. Among the immune parameters, the specific immune competence via ELISA antibody-titer against Newcastle disease and infectious Bursal diseases, following uniform doses of respective-vaccine antigen inoculation and humoral antibody response via anti-sheep RBC antibody titer (during 6 th week) were measured. Juvenile growth traits included the weekly live weight upto 8 weeks and body-confirmation traits during 7 th to 9 th week of age. The analysis of results indicated that cumulative inbreeding to the extent of 30% and beyond definitely, brought significant depression (p< 0.01) in all the weekly body-weight measures up to 6 weeks of age, as compared to the non-inbred birds. While, the trend was not that severe in the body-confirmation traits (breast angle, shank length, keel length). Among the immune traits, the anti-ND immunity was significantly superior in the NB group (ELISA titer: 4503) than the FS (titer: 3157) and HS (titer: 2664) groups, while for the anti-IBD immunity, NB and FS groups shared the superiority over HS group (p<0.05). There was, however, no significant difference between the inbred and NB groups, for general immune-competence (anti-SRBC response). The study concluded that besides the inbreeding depression that was expected for fitness traits, the growth rate and specific defense mechanism of the birds to diseases like ND and IBD were affected as a result of inbreeding beyond a coefficient level of 30 percent.