Cattle Reproduction

What is the difference between Oestrous/Estrous and Oestrus/Estrus?

• Oestrous/Estrous: the reproductive cycle phases in female mammals.

• Oestrus/Estrus: specific to the period of receptivity to mating within that cycle.

What are the two main ovarian structures and state their function.

1. Follicle: Fluid-filled blister containing oocyte(egg) that produces estrogen (estradiol).

2. Corpus Luteum: Solid yellow gland at site where follicle rupted and ovulated that produces progesterone.

What is the purpose of Estrogen/Estradiol and Progesterone?

1. Estrogen: Standing heat and prepares uterine tract for mating.

2. Progesterone: Maintain pregnancy and keeps reproductive system stagnant.

What occurs when progesterone is high and state the phase.

• Uterus prepares for fetus and brain signals are inhibited from ovulation and new follicular development.

• Luteal Phase is long

What occurs when progesterone is low and state the phase.

• Estrogen is dominant; standing heat and triggers the brain to release ovulation signals.

• Follicular Phase is short

Define and state which animals are considered non-seasonal polycyclic/polyestrous.

• Animals that undergo multiple estrous cycles throughout the year, regardless of the season.

• Cattle, pigs, and humans.

Define and state which animals are considered seasonal polycyclic.

• Animals limited to certain seasons of the year.

• Sheep, goats, and deer.

Define and state which animals are considerde monoestrous.

• Animals having one estrous cycle per breeding season, often exhibiting a brief period of receptivity.

• Dogs and bears.

Apart from factors affecting puberty onset (breed & nutrition) in bovine, what is the usual time period for puberty?

7–18 months (average: 10 months).

What is the average oestrous cycle length?

• 18–24 days (average: 21 days)

What does follicular wave mean in bovine reproduction?

Synchronous growth and regression of ovarian follicles.

How many waves are in one Estrous cycle and how much days are for each?

• 2 to 3 follicular waves per cycle, lasting 7–10 days per wave.

How does the Hypothalamic-Pituitary-Gonadal (HPG) axis control bovine reproduction?

• Hypothalamus: Releases GnRH (Gonadotropin-Releasing Hormone) under neural/neurotransmitter influence.

• Anterior Pituitary: Releases FSH (Follicle-Stimulating Hormone) and LH (Luteinizing Hormone) in response to GnRH.

• Ovaries (Target Organ): Produce Oestradiol, Progesterone, and Inhibin to regulate pituitary feedback.

What are the key stages of ovarian follicle development from pool to ovulation?

• Primordial Follicle Pool: Dormant resting pool.

• Growth Initiation: Follicle growth initiated (gonadotropin-independent phase).

• Gonadotropin Responsive: Antrum forms; responds to baseline FSH/LH.

• Gonadotropin Dependent: IGF-regulated wave growth; selection and dominance of preovulatory follicle.

• Ovulation: LH surge triggers rupture of the Graafian follicle.

What sub-phases of the estrous cycle belong to the follicular and luteal phase?

1. Follicular
   - Proestrus
   - Estrus

2. Luteal
   - Metestrus
   - Diestrus

State the sequence the sub-phases of the estrous cycle undergo.

Proestrus → Estrus → Metestrus → Diestrus

What hormonal changes characterize the Pro-oestrus phase?

• Day 19-20

• P4 drops as the CL destroyed by PGF2a; FSH increases to stimulate rapid growth of the dominant follicle.

• Ovarian Features: Regressing CL (1.5–2 cm); growing follicle (1.5–2 cm).

What physical changes characterize the Pro-oestrus phase?

• Swollen vulva, slight mucous discharge, early mounting behavior, moderate uterine tone.

What are the hormonal events of Oestrus?

• Day 0

• Hormonal Profile: GnRH and LH surge cause High E2 levels reach threshold, releasing the ovum; baseline P4, dominant follicle reaches peak size

• Ovarian Features: Pre-ovulatory follicle (2–2.5 cm); regressed CL (1.5 cm).

What are the physical events of Oestrus?

• Marked uterine tone (hypertonic & hyperemic), vulval edema, dilated cervix, thick clear mucous discharge.

How long does the estrus phase last for?

8–12 hours (shorter in modern high-yielding dairy cows).

When does ovulation occur in diary cows?

• 10-14hrs after standing heat ends (or 28-32hrs after standing heat begins)

What ovarian changes occur during the Metoestrus phase?

• Days 1-4

• Ovulation depression forms, progressing to a Corpus Haemorrhagicum (CH) and then an early Corpus Luteum (CL ~1.4 cm within 48h, ± central lacuna).

• Decrease E2 and slow increase of P4

What are some physical signs during the metoestrus phase?

• Metestrous Bleeding at vulva on day 2-3 (capillary breakdown in uterine caruncles from drop in E2); heat 48hrs ago

Which phase does the ovum transport through the oviduct and state the duration.

• Metoestrus

• 3-4 days

What hormonal changes occur in the Diestrus Phase?

• Days 5-17

• CL max size secreting high P4 for 2 weeks

• Atresia of dominant follicles from high progesterone blocking LH surge

What physical features occur in the dioestrus phase?

• Flaccid uterus, closed cervix, palpable CL papilla on the ovary.

Explain the events that occur during luteolysis (Non-pregnancy).

• Endometrium secretes PGF2α between Days 16–18 → CL regression → fall in Progesterone → removes negative feedback on HPO axis → GnRH surge → Pro-oestrus.

When is the optimal AI Insemination window?

• 12-18 hours after onset of standing heat (Mid-oestrus to a few hours after the end of oestrus (the AM-PM rule)).

How long does it take for inseminated sperm to undergo capacitation (biochemical changes needed to fertilize an egg)?

6-8hrs

What is the purpose of the CL?

• The CL determines the length of the oestrous cycle via Progesterone secretion.

How does the CL respond to luteolysis?

• The CL acquires PGF2α receptors and becomes responsive to exogenous luteolysis only after Day 5 or 6 of the cycle.

What endocrine sequence triggers the pre-ovulatory LH surge?

1. Luteolysis causes a drop in P4 from the regressing CL.

2. Removal of Progesterone negative feedback increases GnRH pulse frequency.

3. Increased GnRH drives higher FSH and LH release.

4. Accelerating follicular development produces rising E2 and Inhibin (which selectively suppresses FSH).

5. Oestradiol reaches peak threshold level → triggers positive feedback → Preovulatory LH surge → Ovulation.

What is the primary objective of a dairy reproductive management program?

• Economic success

• Clinical and genital tract examinations

• Data collection, processing, and record keeping

What core record categories should be maintained on a commercial dairy farm?

• Animal Identification: ID, DOB, Vaccination, Health, Calving (dystocia, retained fetal membranes)

• Production and Status: Mastitis, Days in milk, lamness

• Reproduction Data: Breeding/ Heat dates, clinical reproductive findings

What facility considerations are required for different production groups on a dairy farm?

• Replacement Heifers: Proper stanchions/crushes for vaccination, synchronization, and artificial insemination (AI).

• Parturient Cows/Heifers: Clean calving facilities.

• Post-Partum Cows: Dedicated housing.

• Breeding Herd: Proper stanchions/crushes for efficient vaccination, synchronization, and AI.

• Dry Cows: Grazing/housing areas designed to monitor body condition score (BCS) and avoid excessive caloric intake.

• Calves: Individual or group pens.

What is the recommended post-partum evaluation time for clinical herd health reproductive examinations?

Examine all cows at 25–30 days post-partum.

What is the recommended pregnancy examinations time for clinical herd health reproductive examinations?

Perform pregnancy diagnosis at 5–6 weeks post-breeding.

What are some targeted examinations for problem cows?

• Animals with calving complications (dystocia, RFM).

• Problem cows:

  • Repeat breeders: Cows requiring > 3 services without conceiving.

  • ONOs (Open, No Oestrus): Open cows that are > 60 days post-calving and in anoestrus.

  • Cows with abnormal cycles or abnormal vulvar discharges.

What is the calving interval for dairy herds?

12-13 months

How many days are open for dairy herds?

90-100 days

How many breeding attempts are required to successfully get a dairy cow pregnant?

2.0-2.5

What is the average number of days between a cow calving and her first artificial insemination (AI) or natural breeding attempt?

70-75 days

What are clean-up bulls?

Fertile male cattle introduced into a breeding herd to naturally impregnate cows or heifers that failed to conceive through artificial insemination

What are some disadvantages and risks to the introduction of clean-up bulls in dairy herd reproductive management?

• Risk of transmitting venereal diseases.

• Indiscriminate breeding of young/unselected heifers.

• Increased handler danger and farm expense.

• Detrimental to accurate record-keeping if bull services are not diligently recorded.

What are the indications for oestrus synchronization programs?

• Synchronizing oestrus for Artificial Insemination (AI).

• Synchronizing oestrus for Embryo Transfer (ET) donors and recipients.

• Identifying oestrus in individual problem animals.

What are the prerequisites for oestrus synchronization programs?

• Animals must be open (non-pregnant) and cycling.

• Adequate Body Condition Score (BCS) and plane of nutrition.

• Normal genital tract free of pathology or disease.

• Adequate AI restraint facilities.

• Trained personnel for heat detection (unless utilizing Timed AI protocols).

• Key Principle: Synchronization is a management tool, not a substitute for good basic herd management.

What are the two basic physiological approaches to oestrus synchronization in cattle?

• Manipulation of the Corpus Luteum (CL):

  • Administration of Prostaglandin F2α (PGF2α) causes luteolysis of a mature CL (effective between Day 6 and Day 18 of the cycle).

  • Protocols include a single injection scheme (if a functional CL is palpated/identified) or a double injection scheme given 11 days apart.

  • Requirement: A responsive CL and a dominant follicle must be present.

  • Ovsync Protocol: Combines GnRH → PGF2α → GnRH to synchronize both follicular waves and luteolysis for timed AI.
    
    

• Suppression of Ovarian Activity (Progesterone Implants):

  • Uses intravaginal progesterone devices (CIDR, PRID) to mimic a prolonged luteal phase by inhibiting the hypothalamic-pituitary axis.

  • May incorporate GnRH and/or PGF2α into the protocol.

  • Sudden removal of progesterone releases the hypothalamic inhibition, triggering a synchronized LH surge and ovulation.

What factors contribute to "Prolonged Days Open" and "Poor Conception" in dairy cattle?

• Voluntary Wait Period (VWP): Poorly defined policy or inconsistent implementation.

• Estrus Detection Accuracy & Intensity:

  • Inaccurate heat detection or over-reliance on secondary signs.

  • Lack of labor training, management commitment, or record-keeping.

  • Misuse of heat detection aids or milk progesterone testing.

• Animal & Health Factors:

  • Postpartum uterine diseases, lameness/feet & leg problems, poor footing/flooring.

  • Nutritional deficiencies, negative energy balance, environmental heat stress.

• Conception & Insemination Mechanics:

  • Insemination timing (violating the AM/PM rule), semen quality, inseminator technique.

  • Infectious reproductive diseases, toxins, or systemic illness.

What can be used to detect ovulation?

• Behavioral cues (standing heat, mounting, restlessness)

• Visual aids (tail paint, scratch patches, chin-ball markers)

• Activity trackers (collars, leg pedometers)

• Clinical exams (ultrasound, progesterone testing)

What is the sequence of the follicular wave?

Recruitment → Selection → Dominance → Atresia/Ovulation

What two core factors determine the success of Artificial Insemination (AI) in dairy cattle?

• Use of proven sires

• Reliable oestrus detection

What are the primary behavioral and physical signs of a cow "Coming into Heat" (Proestrus / Early Peri-Oestrus)?

• Standing Behavior: Will NOT stand to be mounted.

• Behaviors: Stands and bellows, sniffs and headbutts other cows, attempts to ride other cows.

• Physical Signs: Red, moist, slightly swollen vulva; clear mucous discharge from the vulva.

What is the duration of a cow "Coming into Heat" (Proestrus / Early Peri-Oestrus)?

8 hours

What defines "Standing Heat" (True Oestrus) in dairy cattle?

• Gold Standard Sign: Stands to be mounted when ridden by other cows.

• Associated Signs: Rides other cows, bellows frequently, appears nervous and excitable.

What is the duration of "Standing Heat" (True Oestrus) in dairy cattle?

8-12 hours

What are the behavioral signs of a cow "Going out of Heat" (Metoestral / Post-Oestrus Phase)?

• Standing Behavior: Will no longer stand to be mounted.

• Behaviors: Attempts to ride other cows, smells other cows.

• Physical Signs: Clear mucous discharge from vulva; ± metoestral bleed (post-oestrous bleeding).

What is the duration of a cow "Going out of Heat" (Metoestral / Post-Oestrus Phase)?

14+ hours

What are the recommended observational protocols for effective heat detection based on frequency and timing?

• Frequency: Watch cows 3 times daily for 30 minutes per session.

• Timing:

  • Early in the morning (before milking)

  • Early afternoon

  • Late evening

• Key Rule: Observe when other farm activities are minimal (NOT during milking time and NOT during feeding time).

What are the essential management requirements for visual heat detection?

• Personnel: A dedicated person assigned to heat detection, along with an established backup person.

• Identification: Implement a clear, reliable animal numbering system.

• Observer Behavior: Observers must be familiar to the cows and move through the herd quietly.

• Housing/Space: Provide a large enough area for cows to mingle freely, but compact enough that all cows can be observed at once.

• Social Behavioral Cue: Watch for bulling groups (cattle approaching heat commonly congregate together in sexually active groups).

What secondary heat detection aids and technologies can be used on dairy farms?

• Physical / Visual Aids:

  • Kamar heat detectors (pressure-sensitive tailhead devices)

  • Estrotect scratch-off patches

  • Tail-painting

  • Chin-ball markers on teaser animals
    
    

• Electronic / Technological Aids:

  • Pedometers / Activity monitors

  • Videotaping / Camera surveillance

  • Milk progesterone testing

  • Detailed record-keeping systems

What is the primary conclusion regarding heat detection aids vs. visual observation?

• Heat detection aids provide useful, practical tools, but standing to be mounted is not always demonstrated.

• Technology does not replace good management—visual observation ("looking at the cows") remains critical.

Define Early Embryonic Death (EED) versus Abortion in the bovine, including the critical timeline separating them.

• Early Embryonic Death (EED): Loss of the conceptus from conception up to Day 42 of gestation.

• Abortion: Expulsion of a nonviable or dead fetus between Day 42 and Day 260 of gestation.

What are the four critical developmental periods associated with reproductive dysgenesis in cattle?

• Embryonal

• Foetal

• Intrapartum

• Neonatal

What are the general infectious and non-infectious causes of bovine abortion?

• Infectious Causes: Bacteria, viruses, protozoa, fungi, rickettsia, and chlamydiae.

• Non-Infectious Causes: Hormonal imbalances, chromosomal abnormalities, drug administration (e.g., exogenous steroids, PGF2a), toxic/chemical exposure, nutritional deficiencies, physical trauma, and heat/temperature stress.

Describe the primary routes by which infectious agents gain access to the bovine conceptus or corpus luteum.

• Hematogenous Route (A–E): Infectious agents reach the maternal bloodstream via:

  • (A) Respiratory or upper gastrointestinal (GI) tract

  • (B) Arthropod vectors

  • (C) Lower GI tract

  • (D) Mammary gland

  • (E) Skin wounds or mucosal disruptions

  • Outcome: Hematogenous delivery allows organisms to infect both the maternal and fetal components of the placenta, the fetus itself, or the corpus luteum.
    
    

• Venereal Route (F): Organisms transmitted directly from male to female during coitus (e.g., Tritrichomonas foetus, Campylobacter fetus, IBR/BHV-1).

  • Outcome: Venereal pathogens usually do not block fertilization, but induce low-grade endometritis leading to EED or early fetal death.

How do infectious diseases directly and indirectly affect the bovine reproductive system?

• Direct Effects: Impaired sperm survival or transport in the female tract; direct damage to the embryo causing EED; or late-stage direct fetal infection leading to abortion, stillbirth, or the birth of weak, compromised calves.

• Indirect Effects: Disruption of uterine/endometrial function or infection/inflammation of the maternal placentome, resulting in embryonic death, fetal death with abortion, mummification, or stillbirth.

According to Kirkbride's data, list the ten most common bacterial agents isolated from bovine abortions.

• Actinomyces pyogenes (4.22%)

• Bacillus spp. (3.58%)

• Listeria spp. (1.35%) — behaves as a contagious cause

• Escherichia coli (1.09%)

• Leptospira interrogans (0.88%) — contagious

• Pasteurella haemolytica (0.41%)

• Streptococcus spp. (0.30%)

• Pasteurella multocida (0.29%)

• Salmonella spp. (0.29%) — contagious

• Brucella abortus (0.27%) — contagious

What is the causative agent of bovine campylobacteriosis, how is it transmitted, and what is the primary clinical complaint?

• Causative Agent: Campylobacter fetus subsp. venerealis (CFV).

• Transmission: Insidious venereal transmission during coitus or AI. Bulls are asymptomatic, permanent chronic carriers.

• Primary Complaint: A dramatic drop in herd conception rates due to EED secondary to mild, low-grade endometritis. $40–75\%$ of non-immune females become infected after a single service by an infected bull.

How is Campylobacter fetus subsp. venerealis diagnosed, treated, and controlled?

• Diagnosis:

  • History: Post-service anoestrus or irregular return to oestrus; occasional abortion at 2–4 months.

  • Vaginal Mucus Agglutination Test (VMAT): Detects antibodies in cervical mucus from 6 weeks to 7 months post-infection.

  • Direct Culture: Preputial washings/scrapes (bulls), vaginal mucus, or fetal abomasal contents.

  • Serology: Questionable value.
    
    

• Prevention & Control:

  • Vaccination with CFV bacterin.

  • Use exclusive Artificial Insemination (AI) for at least 2 years.

  • Utilize younger bulls ($<4$ years of age).

  • Cull confirmed infected/carrier bulls.

Detail the species, transmission routes, and environmental stability of Brucella abortus.

• Etiologic Agent: Brucella abortus (bovine); note B. ovis (sheep), B. melitensis (goats/sheep), B. suis (pigs).

• Transmission:

  • Ingestion of contaminated abortion products, fetal membranes, uterine discharges (lochia), infected milk, feed, or water.

  • Mucosal membrane, conjunctival, skin wound, or intact skin penetration.

  • Artificial insemination using infected semen.

• Environmental Resistance: Viable in fetuses and manure in cool environments for 2 months; destroyed by direct sunlight within a few hours.

Explain the pathogenesis, clinical signs, and characteristic gross pathology of bovine Brucellosis.

• Pathogenesis: Ingestion/penetration → local lymph node uptake → transient bacteremia (3 weeks to 3 months) → tropism for gravid uterus and placenta due to erythritol (which drives rapid bacterial multiplication) $\rightarrow$ severe placentitis.
  
  

• Clinical Signs:

  • Late-term abortion (>5mth gestation).

  • Stillborn or weak calves, retained fetal membranes (RFM), and marked drop in milk production.

  • General maternal health is typically unaffected in uncomplicated cases.

  • Bulls: Orchitis, epididymitis, seminal vesiculitis, ampullitis, testicular abscessation, and permanent sterility.

  • Chronic Cases: Endometritis, synovitis, and arthritic joints.

• Pathology: Autolyzed aborted fetus, marked thickening of inter-cotyledonary placental regions, and necrosis of cotyledons.

What diagnostic methods, control strategies, and zoonotic implications apply to Brucellosis?

• Diagnostic Tests:

  • Direct Culture: Placenta, fetal abomasal fluid, fetal lungs.

  • Screening Tests: Milk Ring Test (high false-positive rate); Rose Bengal Card Test (herd-level identification).

  • Confirmatory Serology: ELISA and Serum Agglutination Tests (SAT).

• Prevention & Eradication:

  • It is a Notifiable Disease with no reliable treatment.

  • Vaccination using Strain 19 or RB51 vaccines.

  • Eradication via test-and-slaughter of reactors, bulk milk ring monitoring, and mandatory investigation of all abortion incidents.

• Zoonotic Importance: Causes undulant fever (malta fever) in humans, contracted via unpasteurized milk or handling infected tissues.

Outline the etiologic serovars, transmission, pathogenesis, and pathognomonic lesions of Leptospirosis.

• Serovars: L. pomona, L. hardjo, L. grippotyphosa, L. canicola, L. icterohaemorrhagiae (Caribbean: L. autumnalis).

• Transmission: Contact with infected urine, aborted fetal tissues/fluids, or venereal contact.

• Pathogenesis: Leptospiraemia → pyrexia, multi-organ vascular damage, excretion in milk, chronic localization in urogenital tract → prolonged leptospiruria.

• Clinical Features:

  • Late-term abortions (7–9 months), stillbirths, weak calves, and infertility.

  • Sudden milk drop ("flaccid mastitis" or milk drop syndrome).

• Pathology: Severe fetal autolysis, occasional jaundice, and fetal interstitial nephritis (pathognomonic).

How is Leptospirosis diagnosed, treated, and controlled?

• Diagnosis: Serology (MAT titres); high titres indicate exposure, but titres can drop by the time abortion occurs, making serology best suited for herd-level screening.

• Treatment: Dihydrostreptomycin (25 mg/kg)

• Control: Multivalent 5-way bacterin vaccination every 6 months; segregation from swine, rodent control, and proper farm drainage

What are the clinical and pathological features of Salmonellosis and Listeriosis in aborting cattle?

• Salmonellosis: Late-pregnancy abortions accompanied by maternal pyrexia and severe diarrhea; retained fetal membranes (RFM) are common.

• Listeria spp.: Ubiquitous organism associated with feeding poor-quality, high-pH silage or cross-infection from small ruminants. Causes late-term abortions characterized by yellow/grey necrotic foci in the fetal liver and placental cotyledons.

Describe the reproductive manifestations, transmission, pathology, and vaccination protocols for Infectious Bovine Rhinotracheitis (IBR / BHV-1).

• Etiology: Bovine Herpesvirus-1 (BHV-1).

• Clinical Presentation: Abortion rates range from $5\%$ to $60\%$, typically occurring at $>4\text{ months}$ gestation.

• Transmission: Venereal, contaminated bedding, or semen.

• Pathology: Severe placentitis, advanced fetal autolysis, focal liver necrosis, and intranuclear (IN) inclusion bodies.

• Infectious Pustular Vaginitis (IPV) Form: Incubation 1–2 days; mucopurulent vaginal discharge, vulvovaginal pustules, and ulcers. Resolves in 10–30 days. Rare for systemic respiratory/abortion and IPV forms to occur concurrently in the same animal.

• Vaccination: Killed vaccines in pregnant cows; modified live vaccines (MLV) given $>6\text{ weeks}$ prior to first breeding.

Explain the outcomes of fetal Bovine Virus Diarrhea (BVD) infection relative to gestational timing

• Early Gestation ($<100\text{ days}$): Fetal death resulting in mummification or abortion. Surviving fetuses become Persistently Infected (PI) calves that are virus-positive and antibody-negative.

• Mid Gestation ($\approx 90–140\text{ days}$): Abortion, mummification, or congenital teratogenesis/defect development (e.g., cerebellar hypoplasia, ocular/retinal lesions, epidermal defects).

• Late Gestation ($>150–170\text{ days}$): The fetal immune system reaches immunocompetence. Results in a normal, fully developed term calf that is virus-negative and antibody-positive at birth.

• Diagnostic Strategy: Serology (rising antibody titres) and Virus Isolation (WI) from whole blood or fetal spleen; removal of all PI animals from the herd.

Detail the transmission cycle, clinical presentation, diagnosis, and management of Neospora caninum.

• Epidemiology: Considered the most common cause of infectious bovine abortion worldwide.

• Life Cycle & Transmission:

  • Definitive Host: Dog (passes unsporulated oocysts in feces).

  • Intermediate Host: Cattle and other species (ingest sporulated oocysts in contaminated feed/water).

  • Transmission Mode: Bovine transmission is predominantly vertical (transplacental) via tachyzoites, rather than horizontal.

• Clinical Presentation: Abortion "storms" occurring primarily between 5 and 7 months of gestation; birth of stillborn, weak, or paralyzed calves with neurological defects.

• Diagnosis:

  • IFAT and ELISA (titres $>1:2000$ are highly suggestive).

  • Immunocytochemistry identification of bradyzoites/tachyzoites in fetal brain tissue.

  • PCR assays on fetal brain.

• Control: Off-label chemotherapy (Toltrazuril, Sulfadiazine-Trimethoprim); domestic dog management away from cattle feed/water; vaccines (reduce abortion incidence but do not prevent infection).

What are the features of Trichomoniasis (Tritrichomonas foetus) in cattle?

• Etiology: Tritrichomonas foetus (flagellated protozoan).

• Transmission: Obligate venereal transmission. Bulls are chronic, asymptomatic preputial carriers.

• Clinical Picture: Early Embryonic Death (EED), post-service irregular anoestrus, high herd infertility, post-coital pyometra, and occasional early abortions ($<5\text{ months}$).

• Diagnosis: Direct microscopic observation of preputial washings or pyometra fluid sediment showing characteristic jerky motility; Culture using InPouch TF system; no reliable serology.

• Control: Transition to 100% AI for a minimum of 2 years; cull all infected bulls.

List other protozoal organisms capable of inducing bovine abortion

• Sarcocystis spp. (causes placentitis/caruncle damage in the last trimester).

• Toxoplasma gondii.

• Babesia spp.

Detail the etiology, pathogenesis, diagnostic hallmarks, and pathology of Mycotic Abortion.

• Etiologic Agents: Aspergillus spp. ($75–80\%$ of cases); Mucorales spp. ($10\%$).

• Pathogenesis: Inhalation or ingestion of fungal spores from moldy hay/feed $\rightarrow$ hematogenous spread $\rightarrow$ placentitis and fetal cutaneous lesions.

• Clinical Signs: Late-term sporadic abortion; calves are occasionally born alive.

• Pathology: Leathery, severely thickened inter-cotyledonary placenta with necrotic, ringworm-like cotyledons. Fetal skin lesions resemble ringworm.

• Diagnosis: Direct microscopic identification of fungal hyphae in mucosal scrapings from the placenta, fetal skin, or fetal abomasal contents.

Summarize the diagnostic samples and typical gestational stages for major infectious abortion agents

Infectious Agent	Diagnostic Sample Required	Usual Gestational Stage at Abortion
Brucella abortus	Fetus, placenta, maternal serum	Last half of gestation ($>5\text{ months}$)
Campylobacter fetus	Cervical mucus, fetus, placenta, preputial scrapings	Early Embryonic Death (EED) (2–4 months)
Leptospira spp.	Maternal urine, fetus, maternal & herdmate serum	Late stage (7–9 months) / Any stage
Salmonella spp.	Maternal serum, fetus, placenta	Late pregnancy
BVD Virus	Fetus (spleen), whole blood, maternal serum	Any stage (0–270+ days)
IBR (BHV-1)	Fetus, placenta	Last half of gestation ($>4\text{ months}$)
Epizootic Bovine Abortion (EBA)	Fetus, tick exposure history	Last trimester
Neospora caninum	Maternal serum, fetal brain tissue	4–6 months (or 5–7 months)
Tritrichomonas foetus	Fetus, placenta, cervical mucus, preputial washing	Early Embryonic Death (EED) ($<5\text{ months}$)
Sarcocystis spp.	Uterine caruncle, placenta	Last trimester
Chlamydia spp.	Fetus, placenta	Variable
Aspergillus spp.	Fetus, placenta, fetal skin scrapings	Last trimester

List non-infectious conditions leading to bovine abortion.

• Severe heat stress or prolonged systemic pyrexia.

• Nitrate Poisoning: Causes fetal hypoxia and elevated fetal cortisol production.

• Toxic Plants: Pine needles (Pinus ponderosa), locoweed (causes uterine vasoconstriction/hemorrhage).

• Iatrogenic: Accidental administration of exogenous glucocorticoids or Prostaglandin $\text{F}_{2\alpha}$ ($\text{PGF}_{2\alpha}$).

• Physical Trauma: Environmental injury or movement over steep/hilly terrain.

Outline the field investigation, reporting, and sampling protocol for a bovine abortion inquiry.

• Reporting Policy: ALL bovine abortions must be reported immediately under a standardized cattle abortion reporting protocol.

• Decision Making: The veterinary epidemiologist/physiologist determines which cases require formal field investigation (most cases warrant full investigation).

• Free Government Sampling: Applicable diagnostic sampling should be conducted free of charge by official Government Veterinary Officers.

• Essential Sample Collection Suite:

  1. Whole fetus and/or placenta (cotyledons and inter-cotyledonary areas).

  2. Uterine swabs/discharges (lochia).

  3. Maternal paired serum samples.

  4. Maternal milk sample.