Dairy Cattle Health

Lameness is one of the most important welfare and economic problems in dairy farming, together with mastitis. Prevalence is commonly 15-30%. Causes include ruminal acidosis (SARA), nutritional mistakes, concrete flooring, prolonged standing, and transition-period disorders. Prevention includes a well-balanced ration with appropriate NDF and buffering capacity, comfortable flooring and resting areas, regular hoof trimming (usually twice yearly), and proper transition-cow management. Treatment may include a hoof block, NSAIDs such as meloxicam, and correction of the underlying cause. Regular lameness scoring on a 1-5 scale is recommended.

Reproductive efficiency is one of the economic foundations of dairy farming. Target parameters include conception rate >50%, pregnancy rate >20% per week, and days open <85 days. Common causes include negative energy balance (NEB), especially in the transition period, subclinical hypocalcemia, metritis or endometritis, and cystic ovarian disease. Management includes monitoring transition-period body condition score (target 3.0-3.5), improving estrus detection with visual observation or activity monitors, using synchronization protocols such as Ovsynch or Presynch when appropriate, and performing regular reproductive examinations.

The transition period, from 3 weeks before calving to 3 weeks after calving, is the most critical period in dairy cattle. Common transition disorders include hypocalcemia (milk fever), ketosis related to NEB, fatty liver, metritis, retained placenta, and displaced abomasum (LDA/RDA). Prevention focuses on a negative-DCAD diet with anionic salts when indicated, proper BCS management, balanced energy and protein supply, and adequate vitamin E and selenium supplementation.

Hypocalcemia develops when calcium mobilization after calving is inadequate. Clinical hypocalcemia occurs in about 5-10% of high-producing cows, while subclinical hypocalcemia may affect up to 50%. Clinical signs include inability to rise, muscle tremors, cold extremities, rumen atony, and dullness. Treatment includes slow intravenous calcium borogluconate and sometimes subcutaneous or intramuscular calcium in mild cases. Prevention includes a DCAD diet during the last 3 weeks before calving, oral calcium supplementation after calving, and appropriate vitamin D support. Hypocalcemia also increases the risk of mastitis, metritis, LDA, and ketosis.

Ketosis is a metabolic disease caused by negative energy balance (NEB). Subclinical ketosis is commonly defined as blood BHB >1.2 mmol/L, with a prevalence of about 40-60%. Clinical ketosis is more severe and often defined as blood BHB >3.0 mmol/L. Signs include reduced appetite, drop in milk yield, weight loss, acetone odor on the breath, and occasionally neurologic signs. Diagnosis relies on measuring blood BHB. Treatment may include intravenous glucose, propylene glycol orally at about 300 mL/day, dexamethasone, and niacin support. Prevention depends on good transition-cow BCS management and an energy-dense transition ration.

Displaced abomasum means the abomasum has shifted from its normal position. Left displacement (LDA) accounts for about 85-90% of cases, while right displacement (RDA) accounts for about 10-15% and is often more dangerous. Risk factors include high-concentrate diets, low forage intake, ketosis, hypocalcemia, metritis, and the early postpartum period. Diagnosis is often based on the characteristic ping heard during percussion and auscultation. Treatment may include surgery such as omentopexy or pyloropexy; rolling may offer temporary benefit in some LDA cases. Prevention depends on sufficient effective fiber, good transition-cow management, and prevention of ketosis and hypocalcemia.

Uterine infections are common after calving. Metritis typically occurs within 21 days after calving and is associated with fever and foul-smelling uterine discharge. Clinical endometritis is usually recognized after day 21 and involves purulent discharge. Subclinical endometritis may be diagnosed by PMN >18% between days 21-33. Risk factors include retained placenta, dystocia, hypocalcemia, ketosis, and multiple births. Treatment may include systemic antibiotics such as ceftiofur or ampicillin for metritis, and PGF2α protocols for endometritis depending on the case. Early diagnosis and treatment substantially improve reproductive performance.

Bovine respiratory disease (BRD) is one of the most important causes of illness and death in calves. Key pathogens include Mannheimia haemolytica, Pasteurella multocida, Mycoplasma bovis, BHV-1, BVDV, BRSV, and PI-3. Risk factors include stress, crowding, poor ventilation, cold weather, and transport. Clinical signs include fever >39.5°C, nasal discharge, coughing, labored breathing, and reduced appetite. Treatment often includes antimicrobials such as florfenicol, enrofloxacin, tilmicosin, or tulathromycin. Early treatment is critical. Prevention depends on vaccination, good colostrum management, and adequate ventilation.

BVDV is an important viral disease that causes serious economic loss in dairy herds. A key concept is the persistently infected (PI) animal, which develops when the fetus is infected between approximately days 40 and 120 of gestation. PI animals shed virus continuously and are the main source of infection within the herd. Clinical forms include acute infection with mild diarrhea, fever, and immunosuppression; mucosal disease in PI animals, which is often fatal; and reproductive losses such as abortion and congenital defects. Control relies on identifying and removing PI animals, vaccination, and strict biosecurity.

IBR is an important respiratory and reproductive disease caused by bovine herpesvirus-1 (BHV-1). Clinical forms include a respiratory form with fever, nasal discharge, cough, and conjunctivitis; genital forms (IPV in females and IBP in males); abortion, often between months 4 and 8 of gestation; and occasionally encephalitis in calves. An important feature is latency: BHV-1 remains latent and may reactivate during periods of stress. Control depends on vaccination, including marker vaccines when available, isolation of affected animals, and herd-level control measures.

Johne's disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP), is a chronic progressive intestinal disease. A key feature is that infection usually occurs in calfhood, while clinical signs often appear 2-5 years later. Clinical signs include chronic diarrhea, weight loss, submandibular edema, and reduced milk yield. Diagnosis may involve ELISA, fecal culture, and PCR. Treatment is not considered effective, so affected animals should usually be removed. Control focuses on separating calves from infected cows, colostrum hygiene, testing-and-culling programs, and strong biosecurity.

Brucellosis caused by Brucella abortus is an important zoonotic and reproductive disease. In Turkey it is a notifiable disease. Clinical signs include abortion, especially in the last trimester, retained placenta, and epididymitis in bulls. Human health risk is significant, and infection may occur through raw milk or dairy products. Control in Turkey is based on mandatory vaccination, test-and-slaughter programs, movement control, and pasteurization. There is no effective treatment for infected cattle, so culling is required.

Foot-and-mouth disease (FMD) is an extremely contagious viral disease. In Turkey it is both notifiable and subject to compulsory vaccination. The causative virus belongs to the Aphthovirus genus and has 7 serotypes. Clinical signs include fever, vesicles in the mouth and on the feet, lameness, reduced milk yield, and decreased appetite. Young animals may develop myocarditis and die suddenly. Control includes compulsory vaccination, isolation of affected animals, biosecurity, and movement restrictions.

A vaccination program is one of the foundations of herd health planning. Compulsory vaccines in Turkey include FMD twice yearly, brucellosis in young females, and anthrax in endemic areas. Commonly recommended vaccines include BHV-1/IBR, BVDV, BRD-complex vaccines especially in calves, leptospirosis, rotavirus/coronavirus vaccines given to the dam in late gestation for calf diarrhea prevention, and clostridial vaccines. The exact program should be adapted by the herd veterinarian based on regional risk and herd status.

Neonatal calf diarrhea is the leading cause of death in calves younger than 1 month. Common causes include rotavirus, coronavirus, E. coli K99 in the first 3 days, Cryptosporidium parvum between 3 and 21 days, and Salmonella. Clinical signs include watery diarrhea, dehydration, acidosis, weakness, and inability to stand. Treatment is based on oral rehydration solution, intravenous fluids in severe cases, and targeted antimicrobial use when indicated, such as in Salmonella cases. Halofuginone may be used in cryptosporidiosis. Prevention depends on colostrum management, maternal vaccination before calving, hygiene, and strong biosecurity.

Colostrum is the calf's only source of passive immunity, because antibodies do not pass through the bovine placenta. The 4Q rule is useful: Quantity — about 4 L within the first 6 hours; Quality — Brix refractometer >22%; Quickly — as soon as possible after birth; Quietly/Cleanly — hygienic collection and feeding. The target is serum IgG >10 g/L at 24 hours. Failure of passive transfer substantially increases the risk of BRD and diarrhea. Building a colostrum bank is recommended.

Leptospirosis is an important zoonotic disease caused by Leptospira spp.. Important serovars include L. hardjo, which is adapted to cattle, L. pomona, and L. grippotyphosa. Clinical signs may include fever, hemolysis, hemoglobinuria, jaundice, agalactia, abortion in late gestation, and infertility. Human risk is relevant for farmers and veterinarians, with infection occurring through contaminated urine or water. Control includes vaccination, rodent control, limiting exposure to stagnant water, and antimicrobial treatment such as penicillin or streptomycin when indicated.

SARA is a metabolic disorder caused by prolonged depression of rumen pH. It is commonly defined as rumen pH <5.8 for more than 3 hours per day. Prevalence in high-producing herds may reach 20-40%. Clinical signs include low milk fat, increased milk protein, variable appetite, lameness, diarrhea, and foamy feces. Causes include high-concentrate and low-forage diets, rapid dietary change, and inadequate NDF. Prevention depends on adequate forage-to-concentrate balance, NDF >28-30% of dry matter, buffering agents such as sodium bicarbonate, gradual dietary transitions, TMR use, and monitoring feed intake.

Bovine tuberculosis caused by Mycobacterium bovis is an important zoonotic disease and is notifiable in Turkey. Transmission occurs mainly through the respiratory route and through contaminated milk. Clinical signs may include chronic cough, weight loss, lymph node enlargement, and reduced milk yield, although many animals remain asymptomatic for long periods. Diagnosis relies on the tuberculin skin test and sometimes interferon-gamma testing. Control depends on testing, culling positive animals, and pasteurization to protect human health.

Cystic ovarian disease is an important reproductive problem in dairy cattle. Prevalence is often 10-20% and may be higher in high-producing herds. Main types include follicular cysts associated with inadequate LH surge and anovulation, and luteal cysts associated with insufficient luteolysis. Risk factors include high milk yield, NEB, ketosis, hypocalcemia, and stress. Clinical signs include anestrus, irregular estrus, and sometimes nymphomania with follicular cysts. Diagnosis is based on rectal examination and ultrasonography. Treatment may include GnRH, PGF2α, Ovsynch protocols, and correction of underlying metabolic problems.

Retained placenta means the placenta has not been expelled within 24 hours after calving. Prevalence in normal herds is often 3-12%. Risk factors include dystocia, twins, abortion, hypocalcemia, selenium/vitamin E deficiency, and BVDV. Complications include metritis, endometritis, ketosis, LDA, and reduced reproductive performance. Management no longer routinely includes manual removal because it may increase the risk of metritis. Supportive care, monitoring, and systemic antibiotics in selected cases may be used. Prevention relies on good calving management and adequate selenium plus vitamin E status.

Teat-end condition is an important indicator of mastitis risk. A common 1-5 scoring system is: 1 normal and smooth, 2 mild ring formation, 3 clear ring and roughening, 4 severe ring and cracking, and 5 very severe damage. The goal is for more than 80% of cows in the herd to remain at scores 1-2. Common causes of high scores include milking machine problems such as excessive vacuum or overmilking. Corrective actions include milking system calibration, milking routine optimization, and consistent pre- and post-dipping. Teat-end scoring should be reviewed regularly, often monthly.

Herd health management means moving from treating individual sick animals to a proactive herd-based approach. Core components include regular veterinary visits, analysis of production data such as milk yield, SCC, and reproductive performance, monitoring disease incidence, a structured vaccination program, biosecurity protocols, and regular nutritional review. Key performance indicators (KPIs) may include SCC <200,000 cells/mL, mastitis incidence <25 cases/100 cows/year, lameness prevalence <10%, pregnancy rate >20% per week, and calf mortality <5%. Regular data review and close cooperation with the herd veterinarian are essential.

Selenium and vitamin E are critical components of antioxidant defense. Deficiency consequences include white muscle disease in calves, increased retained placenta risk, poorer mastitis resistance, reduced reproductive performance, and impaired immune function. In Turkey, soil selenium levels are low in many regions. Supplementation may use organic selenium such as selenomethionine or inorganic sources such as sodium selenate, with a maximum safe total dietary level of about 0.3 mg/kg dry matter. Vitamin E is often supplemented at 1000-3000 IU/day during the transition period. Selenium toxicity is possible, so overdosing must be avoided.

Heat stress is a major issue in dairy production in hot climates such as Turkey. Thresholds commonly used are THI >68, when milk yield begins to decline, and THI >72, indicating serious heat stress. Effects include milk losses of 10-25%, reduced feed intake, poorer reproductive performance, immunosuppression, and increased SARA risk. Management includes fan-plus-sprinkler cooling systems, shade, easy access to cool clean water, feeding more during the night, increasing dietary energy density when needed, using buffers, and supplementing potassium.

Antimicrobial resistance is a major issue in veterinary and public health. Core principles include selecting drugs based on culture and susceptibility whenever possible, avoiding broad-spectrum drugs unless necessary, respecting treatment duration, and observing milk and meat withdrawal times. Critically important antimicrobials such as fluoroquinolones and third- or fourth-generation cephalosporins should be reserved for necessary cases. In mastitis control, culture-based treatment and selective dry cow therapy are preferred. All antimicrobial use should be documented, and veterinary prescription and oversight are essential.

Biosecurity means the measures used to prevent disease entry into the herd and spread within the herd. External biosecurity includes quarantine of new animals for 21-30 days, testing purchased animals for problems such as BVDV-PI, Johne's disease, and brucellosis, visitor control, vehicle disinfection, and protection of feed and water sources. Internal biosecurity includes isolating sick animals, separating age groups, cleaning and disinfecting equipment, controlling rodents and birds, and proper carcass disposal. A herd biosecurity plan should be developed together with the herd veterinarian.

Animal welfare is critical both ethically and for productivity. Key Welfare Quality® indicators include lameness prevalence (target <10%), BCS distribution, cleanliness score, injury and swelling scores, lying behavior (usually >12 hours/day), respiratory difficulty, and nasal discharge. The Five Freedoms remain the basic framework: freedom from hunger and thirst, discomfort, pain/injury/disease, restriction of normal behavior, and fear/distress. Regular welfare assessment is both good practice and increasingly a legal or market requirement.