AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

Autosexing in chicken

SEX-LINKED INHERITANCE AND AUTOSEXING IN CHICKEN

• In birds, moths, butterflies, silkworm and in some fishes, different kinds of sex linkages occur where males are homogametic and females are heterogametic.
• In poultry sex chromosomes are described as “ZZ” in males and “ZW” in females.
• The general principle for autosexing in fowls is that homogametic sex (male) should have the recessive character in homozygous condition and heterogametic sex (female) should have the dominant character.

Autosexing is when pure bred day old chicks can be sexed by their different appearances when they have hatched.

• The 'barring' pattern is sex-linked. That is the males have two chromosomes for barring and the females only one, resulting in day old chicks have a light coloured patch on the top of the head.
• When the barring is combined with brown colouring, the light spot on the head of the females is small and well defined and in addition, there is a very clearly defined stripe down the body.
• The male chicks on the other-hand have a light patch covering most of the head and there is only a very blurred, indistinct body stripe. The down of the male chick is much paler.
• The first autosexing breed was developed and described by Punnett and Pease (1930).
• Some autosexing traits in poultry:
  • Barring and non-barring in Plymouth Rock
  • Silver plumage in Sussex x Golden plumage in Rhode Island Red and New Hampshire
  • Rapid feathering x Late feathering