BASC108A – Module 7 Study Notes: Bovine Reproductive System

Female Reproductive Anatomy (Cow)

• Macroscopic parts

  • Ovary

  • Homologous to the male testicle; site of gametogenesis.

  • Potential ova: $20\,000$ per ovary in cattle vs. $400\,000$ per ovary in human females.

  • Fully developed at puberty; ova number is finite (no post-natal production).

  • Two functional ovaries in almost all mammals (exception: hen – only the left ovary functional).

  • Infundibulum → Oviduct (a.k.a. fallopian tube)

  • Infundibulum sweeps ovulated ovum into the oviduct.

  • Oviduct length: cattle $25\,\text{cm}$; buffalo $28.2\,\text{cm}$.

  • Uterus

  • Body + two uterine horns (divided anterior end).

  • Horn length (cow) $35\text{–}40\,\text{cm}$; body $2\text{–}4\,\text{cm}$.

  • Ewe & mare share same pattern; sow has two horns but essentially no body; woman has only a body (no horns).

  • Cervix

  • $2\text{–}3$ inches long; normally closed by annular rings/folds.

  • Opens during estrus & parturition.

  • Vagina

  • Organ of copulation; receives penis & semen; birth canal.

  • Vulva (external genitalia)

  • Composed of labia, clitoris, vestibule; common opening for urinary & genital tracts.

  • Bladder – stores urine; lies ventral to reproductive tract.

  • Rectum – dorsal landmark for palpation; above reproductive tract.

Ovarian Endocrine Functions

• Estrogen secretion →

  • Little/no muscle growth, mammary gland development, development of genitalia, fat deposition on hips & stomach (energy reserve), triggers behavioral heat.

• Corpus luteum (CL) formation after ovulation.

• Major ovarian roles:

  1. Gamete production

  2. Estrogen secretion

  3. CL production & progesterone secretion

Quantitative Measurements: Cow vs. Buffalo (500 kg vs. 700 kg reference)

• Ovary size (L × W): buffalo $2.2\text{–}2.9 \times 3.0\text{–}4.0\,\text{cm}$; cow $2.8\text{–}3.8 \times 5.0\text{–}9.4\,\text{cm}$.

• Largest follicle: buffalo $1.4\text{–}1.7\,\text{cm}$; cow $1.9\text{–}2.2\,\text{cm}$.

• Mature CL: size buffalo $1.3\text{–}1.6\,\text{cm}$, weight $0.7\text{–}1.5\,\text{g}$; cow $1.7\text{–}3.0\,\text{cm},\;1.2\text{–}2.5\,\text{g}$.

• Ovum diameter identical: $169\,\mu\text{m}$.

Female Reproductive Phenomena

• Sequence

  1. Ovulation – release of ova; infundibulum transfers to oviduct.

  2. Estrus (heat) – receptivity; standing heat mandatory for breeding.

  3. Gestation – fertilization to parturition; embryo develops in uterus.

  4. Parturition – birth of fully developed young.

  5. Lactation – milk synthesis & let-down.

• Ovulation rates (typical per estrus)

  • Cow & mare: $1$; ewe: $1\text{–}3$; sow: $10\text{–}20$; hen: $\approx 28$ eggs month.

Estrus Cycle Phases (Cow/Carabao vs. Ewe/Doe)

• Follicular Phase = proestrus + estrus (follicle growth).

• Luteal Phase = metestrus + diestrus (CL dominance).

• Anestrus – extended sexual quiescence.

• Cattle: polyestrous year-round; sheep & goats: seasonally polyestrous.

Female Hormones

• Estrogen – initiates puberty, post-partum return to cycles.

• Progesterone (from CL) – inhibits subsequent heats, prepares/maintains uterus for pregnancy.

• FSH – follicular growth.

• LH – ovulation trigger & CL formation.

• CL products – progesterone + relaxin (loosens pelvic ligaments at parturition).

• Unfertilized egg → CL regresses after $\approx 10$ d → corpus albicans (scar).

Species-Specific Reproductive Parameters

Male Reproductive Anatomy (Bull)

• External structures

  • Scrotum – keeps testes $4\text{–}5^\circ\text{F}$ cooler than core temp.

  • Penis with sigmoid flexure + retractor muscles (keeps organ S-shaped inside sheath when flaccid).

• Internal structures

  • Testicles – sperm & testosterone production.

  • Epididymis (head → body → tail)

  • Passage, storage, nourishment & maturation of sperm.

  • Blockage (injury/epididymitis) causes temporary or permanent sterility.

  • Vas deferens – transports sperm to urethra; becomes ampulla near urethral junction.

  • Urethra – common duct for urine & semen.

• Accessory glands

  • Seminal vesicles – fructose & citric acid for sperm nutrition.

  • Prostate – cleans urethra, supplies minerals & fluid; contributes characteristic semen odor.

  • Cowper’s (Bulbourethral) glands – paired; flush urethra pre-ejaculation.

Spermatozoa Characteristics

• Overall length: $68\text{–}74\,\mu\text{m}$ (bull).

• Head: oval, compact chromatin; acrosome facilitates oocyte penetration.

• Tail: neck → middle → principal → end piece; axoneme drives motility.

• Common abnormalities: pear/double heads, coiled/double tails, swollen midpiece, abnormal acrosome, hair rings, frenulum issues.

Male Hormone

• Testosterone

  • Develops & maintains male tract.

  • Secondary sex traits (crest, muscled shoulders).

  • Libido & sexual behavior.

  • Promotes skeletal/muscle growth.

  • Essential for normal spermatogenesis.

Calving-Date Estimation Rule (Gestation ≈ $283$ d)

• Practical mnemonic ("\minus3\, +10" method):

  1. Subtract $3$ months from breeding month.

  2. Add $10$ days to breeding day.

  3. Adjust year as required.

• Example 1: bred July 7 → April 17 the next year.
  $\text{July 7} - 3\,\text{months} = \text{April 7}; +10\,\text{days} = \text{April 17}$.

• Example 2: bred Feb 1 → Nov 11 the same year.
  $\text{Feb 1} - 3\,\text{months} = \text{Nov 1}; +10\,\text{days} = \text{Nov 11}$.

Essential Terminology

• Age of Puberty – onset of sexual maturity.

• Gestation – conception to birth.

• Estrus period – time female accepts male.

• Estrus cycle – interval between heats.

• Ovulation – follicle rupture releasing ovum.

• Parturition – act of giving birth.

• Lactation – milk secretion post-partum.

• Copulation – mating act.

• Fertilization – union of sperm & ovum.

• Nidation – implantation of embryo in uterus.

• Weaning – removal of young from dam’s milk.

These notes capture all anatomical details, quantitative comparisons, physiological processes, hormonal controls, species differences, practical calving calculations, and essential vocabulary presented in Module 7 of BASC108A.