Relationships between bilateral asymmetry and tonic immobility reaction orheterophil to lymphocyte ratio in five breeds of chickens

Bilateral asymmetry of several morphological traits, tonic immobility react ion, and leucocyte ratio were studied in hens and cocks from four Spanish b reeds of chickens (Castellana, Buff Prat, Red Villafranquina, and Barred Re d Vasca) and an F-2 cross between Castellana and Buff Prat (C x BP - F-2) A ny two or all three types of bilateral asymmetry (fluctuating asymmetry, di rectional asymmetry, and antisymmetry) occurred together for the same trait in the different breeds. There was a significant difference in relative as ymmetry among breeds (P < 0.05) for feather and spur lengths in males, and considerable negative heterosis for relative asymmetry of leg and wing leng ths in C x BP - F-2 males (-38 and -12%, respectively). The degree of relat ive asymmetry varied among traits and was between 3 and 12 times greater fo r spur length in males and for wing bay area in Villafranquina males. There were significant differences among breeds (P < 0.05) for tonic immobility duration. The duration of tonic immobility was positively associated with t he mean relative asymmetry of all traits in females from the Villafranquina breed (r = 0.32; P < 0.05), but this finding was not consistent across the different breeds. No significant difference was found among breeds in term s of heterophil to lymphocyte ratio. Although there was no significant asso ciation between mean relative asymmetry of all traits and heterophil to lym phocyte ratio, males from the Villafranquina breed had a positive and signi ficant relationship between relative asymmetry for wing bay area and leucoc yte ratio (r = 0.34; P < 0.05). These results suggest that relative asymmet ry measures did not provide a general tool to assess fear or stress suscept ibility.