Req 2 — Livestock Diseases

Keeping livestock healthy is one of the most important responsibilities in animal science. Diseases can spread quickly through a herd or flock, causing suffering, lost production, and economic hardship. This requirement asks you to identify two diseases for each of the seven livestock categories and understand how they work — symptoms, transmission, and prevention.

Understanding Livestock Disease

Before you research specific diseases, it helps to understand how diseases are categorized:

• Infectious diseases are caused by bacteria, viruses, fungi, or parasites and can spread from animal to animal.
• Non-infectious diseases are caused by nutritional deficiencies, genetic conditions, or environmental factors and do not spread between animals.
• Zoonotic diseases can spread from animals to humans — these are especially important to understand for your own safety.

Diseases by Category

Below are examples of diseases that affect each livestock category. You should research two per category — these examples will get you started, but your counselor may ask you to choose different ones.

Horse Diseases

Horses are susceptible to many conditions. Equine influenza is a highly contagious respiratory virus that causes fever, coughing, and nasal discharge. It spreads through airborne droplets and can be prevented with annual vaccination. Colic is not a single disease but a general term for abdominal pain — it can be caused by gas, impaction, or twisted intestines. Colic is the leading cause of death in horses and is often related to feeding practices, sudden diet changes, or stress.

Dairy Cattle Diseases

Mastitis is an infection of the udder and is the most costly disease in the dairy industry. Symptoms include swollen, hot quarters; abnormal milk (clots, watery, discolored); and reduced production. It is caused by bacteria entering the teat canal and is prevented through clean milking practices and proper sanitation. Bovine viral diarrhea (BVD) causes fever, diarrhea, respiratory problems, and reproductive failure. It spreads through direct contact and can be prevented with vaccination.

Beef Cattle Diseases

Bovine respiratory disease (BRD), often called “shipping fever,” is the most common and costly disease in beef cattle. Symptoms include coughing, nasal discharge, fever, and loss of appetite. Stress from transportation, commingling, and weather changes triggers outbreaks. Prevention includes vaccination, low-stress handling, and good ventilation. Blackleg is a rapidly fatal bacterial disease that causes sudden death, swelling in the muscles, and high fever. It is prevented through vaccination — most cattle receive the vaccine as calves.

Sheep Diseases

Foot rot causes lameness, swelling between the toes, and a foul smell. It is caused by bacteria that thrive in wet, muddy conditions and spreads through contaminated ground. Prevention includes keeping pastures well-drained and trimming hooves regularly. Ovine progressive pneumonia (OPP) is a slow-progressing viral disease that causes weight loss, difficulty breathing, and udder hardening. It spreads through respiratory secretions and infected colostrum, and there is no vaccine — prevention relies on testing and culling infected animals.

Hog Diseases

Porcine reproductive and respiratory syndrome (PRRS) causes reproductive failure in sows and respiratory disease in piglets. Symptoms include stillbirths, weak piglets, and labored breathing. It spreads through direct contact and airborne transmission. Prevention involves strict biosecurity and vaccination. Swine influenza causes fever, coughing, sneezing, and reduced appetite. It spreads rapidly through a herd via respiratory droplets and is prevented through vaccination and biosecurity measures.

Poultry Diseases

Newcastle disease is a highly contagious viral disease that causes respiratory distress, greenish diarrhea, and nervous system problems (twisted necks, circling). It spreads through direct contact with infected birds or contaminated equipment. Vaccination is the primary prevention method. Coccidiosis is caused by a parasite that damages the intestinal lining, leading to bloody droppings, weight loss, and death in severe cases. It spreads through contaminated litter and is prevented with medicated feed and good sanitation.

Goat Diseases

Caseous lymphadenitis (CL) causes abscesses in the lymph nodes, particularly around the head and neck. The bacteria spread when abscesses rupture and contaminate the environment. Prevention includes isolating infected animals and vaccinating where available. Caprine arthritis encephalitis (CAE) is a viral disease that causes swollen joints, lameness, and progressive weight loss. It spreads primarily through infected colostrum from doe to kid. Prevention involves testing the herd and feeding pasteurized colostrum to newborn kids.

How to Organize Your Research

For each of the seven categories, you need two diseases. That is 14 diseases total. A table is a great way to organize this information for your counselor meeting.

Now let’s move from disease to nutrition — starting with how different animals digest their food.