(a) Explain various biological samples to be collected for laboratory investigation in bovines along with the tests which can be…

(a) Biological Samples and Laboratory Investigations

The rationale for sample collection is to obtain material that accurately reflects the pathophysiological state of the animal while maintaining diagnostic validity through proper handling.

Blood is the most versatile sample. It is collected via jugular venipuncture using specific tubes: EDTA for hematology (complete blood count, differential leukocyte count), heparin for plasma-based biochemical panels (liver/kidney function, electrolytes), and plain tubes for serum (serology). Serum is used for antibody tests: Rose Bengal plate test, STAT, ELISA and CFT for brucellosis, the FMD non-structural protein ELISA (DIVA) and liquid-phase blocking ELISA for vaccine response, and ELISA for IBR and bovine leukosis. EDTA whole blood serves for PCR (for example trypanosomes, theileria and lumpy skin disease virus). Thin blood smears stained with Giemsa or Leishman show haemoprotozoa such as Babesia, Theileria, Anaplasma and Trypanosoma evansi, and lymph node aspirates show Koch's blue bodies of Theileria. Proper anticoagulant mixing is vital to prevent clotting artifacts.

Milk is essential for reproductive and metabolic health. The California Mastitis Test (CMT) and Somatic Cell Count (SCC) assess subclinical mastitis. Bacteriological culture and sensitivity testing identify specific pathogens like Staphylococcus aureus or E. coli. Milk also serves for the milk ring test (MRT) for brucellosis screening of herds, residue testing, and progesterone assays to monitor estrous cycles and early pregnancy.

Urine is collected via catheterization or mid-stream catch. It is analyzed for urinary tract infections (culture), metabolic disorders (ketones, glucose), and drug residue testing.

Feces are collected fresh for parasitology (fecal egg count, flotation for Haemonchus and sedimentation for Fasciola) and bacteriology (Salmonella, Campylobacter), and faecal culture, PCR or Ziehl-Neelsen smears for Johne's disease (paratuberculosis); it is also used for viral detection in rotavirus and coronavirus diarrhoea of calves and in BVD.

Skin Scrapings are taken from lesions for dermatophyte culture (ringworm) or mite identification (psoroptic mange).

Vesicular epithelium and fluid from mouth or foot lesions, sent in 50% glycerol-phosphate buffer on ice, is used for FMD virus typing by sandwich ELISA and RT-PCR; oesophageal-pharyngeal (probang) samples detect carrier animals. Skin nodules and scabs are used for PCR in lumpy skin disease.

Genital samples: preputial washings for Trichomonas and Campylobacter fetus, vaginal and cervical mucus, and semen for evaluation and disease screening. After abortion, the fetal stomach contents, placenta (cotyledons) and uterine discharge are cultured and stained (modified ZN for Brucella).

Cerebrospinal Fluid (CSF) is collected via cisternal puncture for neurological cases, tested for protein, cell count, bacteria and magnesium (in grass tetany). Rabies is confirmed after death on brain tissue by the fluorescent antibody test, and BSE, never reported in India, also only on post-mortem brain tissue.

Tissue Biopsies are excised for histopathology to diagnose neoplasms, chronic infections, or systemic diseases. Post-mortem tissues are sent fresh on ice for culture, in 50% glycerol saline for virology, and in 10% formalin for histopathology. All samples must be labelled, packed and transported in appropriate media (e.g., Cary-Blair for enteric bacteria, cold chain for serology), with a history, to prevent degradation; blood smears from a suspected anthrax carcass are taken from an ear vein without opening the carcass.

(b) Conventional Vaccines and Indian Disease Context

Conventional vaccines induce immunity by presenting pathogen antigens to the immune system without causing disease. They are broadly classified into three types:

1. Live Attenuated Vaccines: These contain weakened pathogens that replicate in the host, stimulating both humoral and cellular immunity. They generally require fewer boosters but may revert to virulence in immunocompromised animals. In India, these are used for Brucellosis (strain S19 for female calves of 4–8 months under the NADCP; RB51 is used in some other countries), Anthrax (Sterne 34F2 spore vaccine), PPR of sheep and goats (Sungri/96 strain), Theileriosis (the Theileria annulata schizont cell-culture vaccine), Lumpy skin disease (Lumpi-ProVacInd, 2022), Sheep pox and goat pox, Classical swine fever (cell-culture vaccine), and poultry diseases such as Ranikhet disease (F, LaSota and R2B strains), Marek's disease (HVT), Infectious bursal disease and fowl pox.
2. Killed/Inactivated Vaccines: These use pathogens killed by heat or chemicals. They are safer but often require adjuvants and multiple doses to achieve protective immunity. Examples in India include Foot and Mouth Disease (FMD) (trivalent O, A and Asia-1 oil-adjuvant vaccine, given every six months under the NADCP), Rabies (cell-culture inactivated vaccine), Haemorrhagic Septicaemia (alum-precipitated/oil-adjuvant), Black Quarter (Clostridium chauvoei), and Enterotoxemia (Clostridium perfringens).
3. Toxoid Vaccines: These use inactivated bacterial toxins to induce immunity against toxin-mediated diseases. The primary example in India is the Tetanus toxoid, often combined with other clostridial vaccines; the enterotoxaemia vaccine is itself largely an anaculture-toxoid of Clostridium perfringens type D.

Note: Subunit and recombinant vaccines are considered advanced or non-conventional technologies and are distinct from the classical categories above.

(c) Pelvic Cavity Boundaries and Contents

The pelvic cavity is a rigid bony compartment formed by the sacrum, coccygeal vertebrae, and paired os coxae (ilium, ischium, pubis).

Boundaries:

• Dorsal: Sacrum and coccygeal vertebrae.
• Lateral: Shafts of the ilia and the sacrotuberous (sacrosciatic) ligaments.
• Ventral: Pelvic floor formed by the pubis and ischium.
• Cranial (Inlet): bounded by the sacral promontory dorsally, the shafts of the ilia (arcuate lines) laterally and the pecten of the pubis ventrally. In the cow the inlet is oval and more upright than in the mare, and the pelvic floor slopes upwards caudally.
• Caudal (Outlet): Defined by the first coccygeal vertebrae, the sacrotuberous ligaments and the ischial arch. The obturator foramina are skeletal openings in the os coxae, not contents of the cavity.

Contents:

• Common to both sexes: the rectum (dorsally), the terminal parts of the ureters, the internal iliac vessels, the pelvic and pudendal nerves, and lymph nodes. The peritoneum extends into the cranial part of the cavity, forming the rectogenital and vesicogenital (in the female) pouches; the caudal part is retroperitoneal.
• Male Bovines: The urinary bladder (its neck; the body lies on the pelvic floor only when empty), pelvic urethra with urethral muscle, ampullae of the ductus deferens, vesicular glands, the disseminate part and small body of the prostate, and bulbourethral (Cowper’s) glands. These accessory glands can be palpated per rectum.
• Female Bovines: The urinary bladder, pelvic urethra, vagina with the vestibule caudally, cervix, and the body of the uterus; in heifers and non-pregnant young cows the horns also lie largely within the pelvis, but in older, multiparous or pregnant cows the uterus sinks over the pelvic brim into the abdomen. Crucially, the ovaries are not pelvic contents; they are abdominal organs suspended by the mesovarium, positioned cranial to the pelvic inlet.

Clinical Significance: Understanding these boundaries is vital for dystocia management. In females, the relatively narrow, upward-sloping pelvic canal with prominent ischial tuberosities makes dystocia commoner in cattle than in mares and necessitates precise assessment of fetal presentation, position and posture. Pelvic measurement (pelvimetry) of heifers helps predict calving difficulty, and the pelvic location of the reproductive tract makes rectal palpation for pregnancy diagnosis and AI possible. In males, rectal palpation of the accessory glands (for example in seminal vesiculitis) and knowledge of the pelvic urethra aid in managing urethral obstruction.