Sexual Dimorphism for Coping Styles Complements Traditional Methods for Sex Determination in a Multivariety Endangered Hen Breed

Abstract

Sex determination is key to designing endangered poultry population conservation and breeding programs when sex distribution departs from Hardy–Weinberg equilibrium. A total of 112 Utrerana chickens (28 per variety, partridge, black, white, and franciscan) were selected for hatching day sexing. Sex assignation was performed through 10 methods. Three sex assignment criteria comprised criteria found in literature, opposite criteria to that in the literature, and composite criteria combining methods reporting the highest predictive success from the previous ones. This study aims to determine which method combinations may more successfully determine sex across the four varieties of Utrerana endangered hen breed to tailor noninvasive early specific models to determine sex in local chicken populations. Although the explanatory power of the three assignation criteria is equal (75%), assignation criteria 2 resulted to be the most efficient as it correctly assigns males more frequently. Only methods 3 (English method), 5 (general down feathers coloration), 7 (wing fan), and 10 (behavior/coping styles) reported significant differences regardless of the variety, hence, are appropriate for early sexing. Sex confirmation was performed at 1.5 months old. Identifying sex proportions enhances genetic management tasks in endangered populations, complementing more standardized techniques, which may result inefficient given the implicit diversity found in local populations.

Traditional sexing methods and external egg characteristics combination allow highly accurate early sex determination in an endangered native turkey breed

“…This was due to the fact that some animals died, and others were donated to local farms (as part of an Andalusian turkey breed recovery program) before the sexual dimorphism of the individuals became evident. In the literature, it has been reported that samples of around 100 or even fewer individuals report 95% sexing accuracy in other local poultry species ( 5 , 9 , 26 ). Therefore, of the total of 972 observations that were obtained, only 506 observations were used in the analyzed database, of which the individual sex was confirmed and a complete sexing determination procedure of three appraisers was collected.…”

“…Despite the fact that differences in the reaction to acoustic stimuli between the sexes have been thoroughly studied in chicks (60)(61)(62)(63)(64)(65)(66)(67), the behavior/coping style or "slap" technique has scarcely been reported as a sex discriminant technique. It was only (5) who evaluated its applicability in a chick sex-determining study. In line with these results, the "slap technique" reports significant results supporting its feasible applicability for sex determination in domesticated Meleagris gallopavo which had never been described in turkey species prior to this study.…”

“…Sexing chicks during the first day of life could be a critical step not only in the commercial poultry industry but also in the design of conservational and breeding programs for endangered native breeds, as described by ( 5 ). The use of reliable sexing techniques in endangered avian breeds is of special importance in breeding programs, since it could avoid lowing hatching rate problems or copulation problems due to side effects derived from high inbreeding in such minority populations ( 6 ).…”

“…As a consequence, Andalusian turkey males may be aimed toward the maximization of their meat production while letting hen for the laying aptitude ( 10 ). These sexing methods can also be a beneficial tool when management strategies to preserve genetic diversity are designed, since sex distribution across the population is possibly biased ( 5 ).…”

“…In avian species, sexual dimorphism is caused by several secondary phenotypical traits that can be recognizable even in the laid egg until the 1-day-old poult ( 5 ). Several sex-influenced phenotypical traits in these early stages have been reported, including egg size ( 17 , 18 ), the opacity of the eggshell ( 19 ), feather color, morphology and distribution ( 20 ), appendicular skeleton dimensions, focusing on tarsus-metatarsus length ( 21 ), head length and size ( 22 , 23 ), tail inclination ( 24 ), and the behavioral performance of the individuals ( 22 , 25 ).…”