An exploratory analysis to determine the impact of fixed effects and to establish genetic parameters across six types of ostrich feathers
After a decline in value, ostrich feathers have again become an important part of the income of ostrich producers. Between 22586 and 22753 feather weights, as well as length and width measurements, were obtained from feathers harvested annually during the resting period from a pair-bred ostrich flock maintained at Oudtshoorn Research Farm from 2001 to 2012. The flock consisted mostly of the South African Black (SAB) genotype, but birds from the Zimbabwean Blue (ZB) and Kenyan Redneck (KR) strains were also introduced to study strain effects, as well as the effect of crossbreeding between these genotypes (ZB x SAB; SAB x ZB; KR x SAB; SAB x KR). The feathers were sorted into six feather-type categories, namely floss, short hard body feathers, long hard body feathers, tail feathers, white plumes and short body floss. White plumes had the highest average feather length (AFL), average feather width (AFWD) and square-root-transformed feather weight (SRFW) at 66.2 ± 0.38 cm, 21.2 ± 0.23 cm and 13.66 ± 0.17 g, respectively. A significant decline in AFL took place from 2001 and 2012 (40.0 ± 0.25 cm and 38.7 ± 0.56 cm, respectively), while AFWD stayed fairly constant. Feather weights were higher for males than females resulting in a 24% higher geometric mean for backtransformed feather weights (GMFW) for males relative to females. SAB birds outperformed ZB and KR birds for AFL, AFWD and SRFW. Crosses were intermediate and sometimes comparable with the SAB genotype. Except for long hard body plumes, the weights for all the feather types were higher for the purebred SAB breeders compared with purebred ZB and KR breeders. Heritability estimates of AFL, AFWD and SRFW across the six feather categories were low to moderate at 0.080 ± 0.012, 0.044 ± 0.009 and 0.116 ± 0.017, respectively. The animal permanent environmental effect for the feather traits was lower in magnitude and ranged between 0.025 ± 0.008 for AFL and 0.041 ± 0.012 cm for SRFW. Direct genetic correlations of feather dimensions with SRFW were moderate to high at 0.287 ± 0.117 with AFL and 0.614 ± 0.072 with AFWD. The present results indicate that feather quantity can be improved by genetic selection in ostriches, and further studies should be conducted.
Keywords: Age, feather length, feather weight, feather width, genotype, sex