Resistance


LivestockJust like people, livestock have more resistance to diseases when:

  • their nutritional and water intake needs are met.
  • their living environment is not stressful, and is kept clean.
  • they receive appropriate vaccinations to build up immunity.

Another important factor is an animal's ability to resist diseases, or mount an immune response:

  • Innate immunity - is present without prior exposure to a disease-causing agent. These defenses keep infectious agents out of the body or quickly mount a non-specific response to clear the infection or activate the adaptive immune system.
  • Active or adaptive immunity - acquired through vaccination or by exposure to a disease, can provide long-lasting protection as a result of immunological memory. There is a genetic component to innate and adaptive immunity, so animals can be bred to resist certain diseases.
  • Passive immunity - acquired when antibodies are passed from one animal to another, such as from colostrum, a highly concentrated form of milk produced by the mother right after birth, lasts for a few weeks.

A biosecurity plan can address methods for preventing, monitoring and responding to livestock diseases. It will help you think about and come up with the best answers to these questions:

  • How are disease(s) entering your herd?
  • How can you prevent them?
  • Do you have a plan to contain illnesses when they happen?
  • What could you be overlooking?

In addition to the biosecurity plan, a herd health program is a good strategy for protecting livestock from diseases, parasites and pests. Work with your veterinarian to develop a program for herd health, and evaluate what livestock needs to maintain health and disease immunity.

Ask your regional livestock Extension specialist for recommendations on paper templates and/or computer software that would be helpful for keeping herd health records.

The simple flow sheet example below outlines important events during a cow/calf spring calving system, and when vaccinations should be administered.

Herd health program schedule

Source: Adapted from Designing Preventative Health Management Programs for Cattle Producers, University of Nebraska Great Plains Veterinary Center.


Seven Steps to Whole-herd Health

The recommendations below are for beef cattle, but can be adapted for other livestock. Consult with your veterinarian about setting up a herd health program.


  • Define goals and expectations for your health program.

  • Diseases to prevent

    What’s common in your area and on your ranch?

  • Product selection

    Talk with your veterinarian about what vaccine products are available and why he or she recommends them. The variety is huge and your choices should include considerations for such things as level of protection and duration of immunity.

  • Timing and practicality

    Pick products that will work with your schedule.

  • Recordkeeping

    Programs like Beef Quality Assurance (BQA) are good to use. BQA includes the recording of every health product you use: serial numbers, expiration dates, injection site mapping.

  • Review

    Establish a system of reviewing medications and vaccines and measuring response. Set measurable points such as weaning weights, methods of treating sick animals, etc. Then yearly have a discussion and measure to see whether making improvement.

  • Monitor

    Build your health program around hard evidence. For example, what diseases in the past have your livestock had? What worked to solve the problems? What did necropsies show to be the problems? What is your real percentage calf crop?


Seven Steps Content Source:
Newport, Alan. 2014. Make Vaccination One Step to Build Herd Health Program. Beef Producer. Retrieved from https://www.farmprogress.com/story-make-vaccination-step-build-herd-health-program-14-111307

Nutritional Requirements of Livestock

The essential nutrients required by grazing animals are water, energy, protein, minerals, and vitamins. These nutrients are needed to maintain body weight, growth, reproduction, lactation and health. There are other factors that affect nutritional requirements.

Water

Water is essential for all livestock, and producers should plan for an adequate supply of clean water when designing any type of livestock enterprise. Dirty, stagnant water can lead to inadequate water consumption, which will reduce feed and forage intake and compromise livestock performance. The amount of water required depends on the physiological stage of the animal and the climate. Lactating animals require more water, and the amount of water required increases as atmospheric temperature increases.

For example, at temperatures above 35°C (95°F), cattle require about 8 to 15 liters (2.1 to 4 gallons) of water per kg (2.2 lb) of dry matter intake. Generally, cattle require about 2.6 percent of their body weight in dry matter (DM) intake per day. Therefore, a 1000 lb cow could require as much as 175 liters or 45 gallons of water a day! Daily water consumption of ewes will vary from 0.75 to 1.5 gallons depending on climate and stage of gestation. Water availability should be closely monitored because a deficiency in water will result in death much faster than a deficiency of any other nutrient.

Protein

In most situations, the amount of protein supplied in the diet is more critical than the quality of the protein. Ruminants have the ability to convert low-quality protein sources to high-quality proteins through bacterial action. Microbial protein synthesis is sufficient to supply the protein needs as long as adequate precursors are supplied, except during lactation for high milk producing animals.

Protein is required by all grazing animals for tissue growth and repair. Protein required for a 1000 lb non-lactating cow is around 1.6 pound/day or 7 percent crude protein in the diet. When the cow is lactating, 2.0 lb or 9.6 percent dietary crude protein is required. If protein is deficient in the diet, grazing animals must break down body tissue to obtain sufficient protein. A protein-deficient animal must break down 6.7 pounds of lean body tissue to supply one pound of protein, resulting in severe weight loss.

Energy

Insufficient energy probably limits performance of livestock more than any other nutritional deficiency. Energy requirements vary greatly with stage of production, and adequate amounts of energy are extremely important during late gestation and early lactation. Energy deficiencies can cause reduced growth rate, loss of weight, reduced fertility, lowered milk production, and reduced wool quantity and quality.

Energy is obtained from carbohydrates in the plant material and can be stored in the form of body lipids. However, heavy demands against fat stores as an energy source to meet daily needs may delay estrus and reduce conception in breeding females. Live weight gain can only occur after the animal’s energy requirements for maintenance and lactation are met.

Vitamins and Minerals

Ruminants require all the fat-soluble vitamins (A, D, E, and K), but they can synthesize the B vitamins in their rumen. Normally, the forage and feed supply contain all essential vitamins in adequate amounts, except vitamin A which is obtained as carotene from green plants and is often deficient in dormant forage. However, vitamin A can be stored in the liver in amounts sufficient to last considerable periods of time, such as winter dormancy or prolonged drought.

Salt is essential for many body functions and important to maintain intake of feeds and water. Calcium and phosphorus are needed to maintain growth, feed consumption, normal bone development, and reproductive efficiency. Other nutrients and minerals such as vitamin E and selenium are important for maintenance of healthy bodies and reproduction.

Content Source
Nutritional Requirements of Livestock. 2011. Retrieved from https://articles.extension.org/pages/58189/nutritional-requirements-of-livestock

Factors that Affect Nutritional Requirements of Animals

The nutrient requirements of domestic livestock have been provided in detail by various National Research Council (NRC) publications. However, these NRC requirements have been developed on pen-fed livestock where maintenance requirements are easily calculated and tend to vary only slightly within a given weight, sex, age, and physiological state.

Physiological Stage

The greatest influence on nutritional requirements of livestock is their life stage in production. The key physiological stages in the life of grazing animals are growth (i.e., young animals), late pregnancy, lactation, and maintenance, generally during non-lactating periods. In general, the highest nutritional requirements are for lactation, followed by late gestation, growth, and finally maintenance. Managing livestock production schedules to match nutritional demands with forage quality and availability can greatly improve the efficiency of a production system.

Topography and Climate

The nutrient requirements of grazing animals are also dependent on environmental and climatic variables. Grazing and voluntary travel also require substantial increases in energy expenditure. Range animals walk long distances, climb gradients, and ingest herbage often of low dry matter content, thus spending more time eating and foraging for food. Research estimates that cows grazing rangeland use 30 percent more energy than confined cows because of longer grazing time and longer travel distance.

Climate, particularly temperature, also affects the amount of feed an animal needs to maintain its body functions. As ambient temperature drops, an animal’s metabolic rate increases, and more energy is needed to maintain internal heat. This effect can be exacerbated by wind or wet hide/hair on the animals.

Content Source
Frost, Rachel & Mosley, Jeff. 2015. Factors that Affect Nutritional Requirements of Animals. Retrieved from https://articles.extension.org/pages/58239/factors-that-affect-nutritional-requirements-of-animals

Vaccine Use in Food Animals

When used in food animals, both modified live vaccines and killed vaccines are subject to mandatory withdrawal periods prior to slaughter for human consumption. Animals may not be sent to market until the withdrawal time has elapsed. During the mandatory withdrawal time vaccinated animals or products from vaccinated animals may not enter the food chain. The withdrawal time is determined by the country in which the vaccine is licensed and stated in the product license.

Modified live vaccines replicate in the host and during the withdrawal time live vaccine strain virus may be found in animal products or tissues. Animal products from killed vaccines do not pose an infectious risk, but withdrawal times are imposed to allow the adjuvants to clear from the tissues. Withdrawal times are intended to ensure meat, milk, or other products for human consumption from the vaccinated animal are free from adjuvant or vaccine organism contamination.


Vaccination

Vaccines are used to increase an animal's specific resistance to a disease. Vaccination is the act of giving the vaccine to an animal; immunization is the protective response to the vaccine that you want to stimulate within the animal's immune system.

For nearly all diseases there is a relationship between dose exposure and severity of disease. For diseases that are always present (endemic), reducing the dose of infectious agents the animal is exposed to can positively affect the farm’s economic impact, and help justify the cost of implementing a biosecurity plan.

- Center for Food Security and Public Health

Immunity means an animal's immune system has the ability to be alert for specific infectious agents or disease-causing pathogens. Immunity can reduce the likelihood of clinical signs of a disease, but may not prevent an infection.

Vaccines are meant to supplement other disease control measures, and should not be solely relied upon. Other important risk factors that you identify in a biosecurity plan and herd health program won't be solved by vaccination alone.

  • Animals will sometimes still become sick because pathogens different from those included in the vaccine were involved. The influenza virus is a good example of this.
  • The animal's immune system may be overwhelmed by an infection.
  • The vaccinated animal failed to develop a proactive immune response.
  • During periods of stress (when an animal's immune system may be weaker), animals should not be vaccinated.
  • The animal may have an adverse reaction to a vaccine.
  • Antibiotics are not vaccines.

There is no "standard" vaccination plan for livestock. There are many recommendations on Internet sites, but each livestock operation should evaluate their needs based on their own risks for disease (anticipated exposure, environmental factors, geographic factors, age, breed, use, and sex of an animal), geographic location, cost, etc.

Vaccine Types


  • Modified Live Vaccines

    Derived from the original pathogen or from a closely related pathogen. These vaccines contain live organisms, and are sensitive to damage by improper handling or storage. Because modified live vaccines generally rely on the vaccine organism replicating in the host to produce a protective immune response, these vaccines must be handled carefully. If the organism in the vaccine loses viability, it will not induce an effective immune response. In stressed or immunocompromised animals, some modified live vaccines may cause disease. Some modified live vaccines can cause significant disease if given by the wrong route.  Be sure to follow label instructions. Modified live vaccines should not be used in pregnant animals unless the label specifically states that they are safe for pregnant animals.

  • Killed Vaccines

    Contain part or all of an inactivated pathogen. Killed vaccines generally require an adjuvant to stimulate the host’s immune response and provide protection from disease. An adjuvant is a substance added to vaccines to enhance the capacity to stimulate an immune response. Killed vaccines can contain the whole organism that has been inactivated by heating or chemical denaturation, or they can contain a portion of the organism (subunit vaccine) capable of inducing an effective immune response. Killed vaccines generally need to be combined with an adjuvant by the manufacturer in order to induce a sufficient protective immune response. Killed vaccines often, but not always, require two doses to induce protective immunity on first vaccination.

  • Novel Vaccines

    Developed using new technologies and may be gene-deleted, live-vectored, plant-derived, or DNA delivering.


Tips for Managing Vaccines


Tips Content Source
Vaccination During Animal Disease Emergencies. Center for Food Security and Public Health. Retrieved from http://www.cfsph.iastate.edu/Emergency-Response/Just-in-Time/12-Vaccination-Overview_HANDOUT.pdf

Herd Health Planning Resources

There are species specific resources that provide guidance on best management practices for food safety, animal welfare, worker safety and environmental protection. For instance, Beef Quality Assurance (BQA) is a nationally coordinated, state implemented program that provides training and certification on animal care, handling and production for U.S. beef producers. Majors buyers of beef such as National Beef, Tyson, and Cargill require suppliers to be BQA certified.


Security

Securing your premises, livestock, equipment, agricultural chemicals and supplies can limit disease introductions, and keep animals safe.