Veterinary Anatomy- ICAR JRF/SRF 2024

• Unique Endocrinology of the Bitch (Canis lupus familiaris):
• In most domestic mammals (cow, ewe, mare, sow), luteinization of follicular granulosa cells occurs strictly post-ovulation under the influence of the LH surge.
• In the Bitch:
• Follicular granulosa cells undergo extensive pre-ovulatory luteinization $24 - 48\text{ hours}$ before ovulation in response to the initial rise in baseline LH.
• This causes circulating plasma progesterone levels to rise significantly ($\gt 2\text{ ng/ml}$) prior to follicular rupture, serving as the definitive clinical indicator for timing breeding and artificial insemination.
• nalysis:
• (Bitch): Correct.

Correct option: (4) Bitch

• Equine Mating Behavior:
• Courtship (vocalizing, nuzzling, flehmen, sniffing the mare's flank) is followed by mounting.
• The actual act of mounting, penile insertion (intromission), pelvic thrusts, and ejaculation in horses is rapid, typically lasting approximately $30 - 40\text{ seconds}$ (about 40 seconds), indicated by rhythmic "tail flagging" in the stallion during ejaculation.
• nalysis:
• (About 40 sec): Correct standard copulatory duration.

Correct option: (1) About 40 sec

• Bovine Freemartinism:
• Occurs in over $90\%$ of heterosexual twin pregnancies in cattle.
• Early chorionic vascular anastomoses allow sharing of fetal blood circulation between the male and female co-twins.
• Testicular hormones from the earlier-developing male fetus (Anti-Müllerian Hormone [AMH] and testosterone) enter the female co-twin's circulation:
• Müllerian ducts regress, preventing normal development of the uterus, cervix, and cranial vagina.
• The female co-twin is rendered permanently sterile (Freemartin).
• The male co-twin develops normal reproductive tracts and is typically fertile.
• nalysis:
• (Female is sterile): Correct.

Correct option: (2) Female is sterile