Avian Physiology

• Rose Comb and Subfertility in Roosters:
• Homozygous Rose-comb cocks ($RR$) exhibit a well-documented genetic subfertility syndrome.
• The $R$ allele is associated with a chromosomal inversion that disrupts the sperm motility gene, resulting in abnormal flagellar function and extremely reduced duration of sperm motility in the oviduct storage tubules.

Correct option: (1) Rose comb

• Statement (I) is False: The magnum is the longest anatomical section of the avian oviduct (length $\sim 33\text{ cm}$), whereas the uterus (shell gland) measures only $10\text{ to }12\text{ cm}$.
• Statement (II) is True: In commercial chicken artificial insemination (AI), an insemination dose containing $20\text{ to }25\text{ million}$ motile spermatozoa administered weekly into the vagina achieves over $90\%$ fertility.
• Conclusion: Statement (I) is false, but Statement (II) is true.

Correct option: (4) Statement (I) is false but Statement ({I) is true.

• Recurrent Selection for Specific Combining Ability (Hull, 1945):
• Designed specifically to exploit non-additive genetic variance (overdominance and epistasis).
• Methodology: A heterozygous, genetically segregating foundation population is test-crossed to a constant, homozygous inbred tester line (typically using inbred males / sires as the common tester).
• Selected individuals from the segregating population are intermated in purebred lines based on their crossbred progeny performance with the inbred tester line.

Correct option: (1) Inbred male

• Heritability of Fertility in Poultry:
• Fertility (proportion of incubated eggs that are fertile) is a reproductive fitness trait with very low heritability:

• Because heritability is low ($h^2 \approx 0.04\text{--}0.05$), phenotypic variation is overwhelmingly dominated by environmental, nutritional, management, and mating factors rather than additive genetic variation.

Correct option: (4) 04