ANIMAL SCIENCE
Productivity
By the end of this sub-topic, learners should be able to:
1. Define food conversion efficiency;
2. Identify animal pests and related diseases;
3. Describe how animal pests and diseases affect productivity;
4. Describe ways of preventing animal pests and diseases.
Productivity is the rate of production of new biomass by an individual or animal
population.
Productivity is determined by food conversion efficiency.
Food conversion efficiency (FCE) is the extent to which food consumed by an
animal contributes to increase of its biomass or desired output (like milk in cows or
eggs in layers).
FCE of an individual animal is calculated in grams (g) or kilograms (kg), using the
formula;
F o o d c o n v e r s i o n e f f i c i e n c y= T o t a l m a s s o f f e e d c o n s u m e d M a s s g a i n e d b y
t h e a n i m a l F o o d c on v er s io n ef f i c ien c y = To t a l m a s s o f f ee d c o
n s um ed M a s s g ai n ed b y t he a n im a l
Calculation of FCE helps the farmer to determine the extent to which type of feed
or feeding strategy is profitable.
Several factors affect animal productivity but this section will focus on few selected
diseases and pests.
Anthrax
Spore-forming bacteria (Bacillus anthracis) that usually lives in soil cause the
disease.
It is infectious (transmitted from one animal to another) disease that mainly infects
ruminants or hooved animals (such as, cattle, goats, and sheep) and humans.
Anthrax causes acute mortality because the bacteria produce deadly toxins.
The bacteria can transform into resistant form called spores.
Spores enable the bacteria to survive harsh soil conditions for very long time to
about 50 years.
Animals get the disease by swallowing or inhaling anthrax spores while grazing on
a contaminated pasture.
Signs and symptoms
Bloody discharges from the natural body orifices (openings)
High fever
Infected animals reduce in chewing cud.
Muscle tremors and convulsions.
Difficult in breathing seen shortly before the animal collapses and dies.
The body may not stiffen after death.
Sudden death
Treatment and control
Treat with antibiotics if the disease is quickly identified (but in most cases, it is
helpless to administer treatment due to the acute nature of the disease)
Vaccination of healthy animals
Quarantine animals suspected to be infected
Never open the carcass (dead body) of an animal suspected of dying from anthrax
Isolate carcass from other livestock and protect it from scavengers as much as
possible
Burn but do not bury the infected carcass
Disinfect the death site thoroughly
Foot and mouth
It is a severe, highly contagious disease caused by a virus.
Infected animals shed the virus in expired air, urine, faeces, milk, saliva and semen
up to 4 days before any symptoms are evident.
Indirect transmission of infection can also occur when vehicles, clothing, hands or
feedstuffs get contaminated with the virus and then come in contact with
susceptible animals
Foot and mouth virus can survive for up to 6 months in cool and moist conditions.
Hides, some dairy products and in chilled, cured or salted meats that harbour the
virus for extended periods can also spread the disease.
However, the virus does not survive for long in hot dry conditions.
The foot and mouth virus causes illness in cows, pigs, sheep, goats and other
animals with divided hooves.
Although adult animals usually recover, the morbidity is very high in unsuspecting
populations, and significant pain and distress occur in some species.
Signs and symptoms
Great increase in body temperature for 2 to 3 days
Liquid-filled blisters on feet, tongue, in and around the mouth, nose or snout, and
the teats.
Excess sticky, foamy and stringy saliva
The blisters may rupture, leaving raw, tender skin exposed
Pain and discomfort from the lesions lead to depression, loss of appetite and
weight
Lameness with reluctance to move
Animals reluctant to move or even to rise to their feet
Little or no milk produced
Younger animals may die from foot-and-mouth disease due to sudden heart
failure.
Abortions
Treatment and control
No treatment for infected animals
Vaccination for healthy animals
Quarantine by restricting animal movements and their products to prevent spread
of the disease.
Kill and burn
Disinfecting known and suspected infected areas
Fig.5.1.1:
Burning foot and mouth infected carcasses
Liver damage (Fascioliasis)
It is caused by endoparasites, liver flukes (Fasciola hepatica) – large, flat, leaf
shaped parasites found in the liver.
Endoparasite is any parasite that lives inside its host.
Liver flukes are common in wet regions because their life cycle is dependent on
water.
A liver fluke requires two hosts to complete its life cycle.
The primary host and vector is the water snail whilst secondary host could be
sheep, cattle, goats, horse or even humans.
Fig.5.1.2:
A
mature liver fluke (left) and a water snail (right)
Adult flukes shed thousands of eggs per day that pass down bile duct into
intestines and then eventually deposited onto pasture in faeces or dung.
The eggs hatch into larvae in wet areas such as marshes, riverbanks and around
pools of water.
The larvae multiply in the snails and emerge to attach to the grass as cysts.
Grazing animal ingests the cyst where it breaks out as an immature fluke to make
its way to the liver.
The fluke tunnel through the liver and if conditions are favourable, then a mass
hatch and infection can cause severe and permanent damage.
Fig.5.1.3:
A
cow liver damaged (development of tunnels) by liver fluke infection
The adult fluke live in the bile ducts of the liver where they feed on blood.
This can amount to half a millilitre per adult fluke per day explaining the anaemia
exhibited by infected animals.
Signs and symptoms
Reduced growth rate
Weight loss
Anaemia
Diarrhoea
Reduced milk yield
Increased susceptibility to other infections
Treatment and control
Use flukicides to kill the flukes.
Fence off or avoid wet (especially snail infested) areas in pastures.
Drain away water in pastures if it is cost effective.
Red water
It is a disease caused by infection of the red blood cells of cattle by protozoa
(single-celled parasites).
Red water is a tick-borne disease, referring to the fact that the ectoparasite vector
that spreads the protozoa is the blue tick.
Ectoparasite is any parasite that lives on the outside surface of its host.
Fig.5.1.4:
Blood engorged blue tick
Protozoa that causes red water is injected into the bloodstream by the tick.
It then invades the red blood cells and begins dividing, eventually rupturing the
cell.
Clinical signs begin around 2 weeks after infection.
Effects of red water are relatively mild but there is significant negative impact on
productivity and fertility in affected cattle.
High risk periods for red water are late spring or early summer and autumn but
cases may occur throughout the year, if conditions for ticks are suitable.
Signs and symptoms
Increased temperature (high fever)
Diarrhoea which ceases after around 36 hours and then becomes constipation
Dullness and loss of appetite
Frothy red-brown urine (due to haemoglobin produced by the rupture of the red
blood cells) which becomes darker with time
Pale or yellow mucous membranes
Increased pulse rate (nervousness)
Abortion of pregnant cows
Infected animals stay away from the herd
Treatment and control
Treatment involves keeping the cattle calm, avoiding driving them over long
distances
Administer Berenil or Imizol by deep intramuscular injection.
The dose for Berenil is 5 ml of made up solution (1 packet mixed with 12,5 ml of
sterile water) for each 100 kg (for example, 20 ml for a 400 kg animal)
The dose for Imizol is 1 ml for each 100 kg (for example, 4 ml for a 400 kg animal)
Regular dipping or spraying animals with acaricides (chemicals that kill ticks)
Pasture management (clear scrub and prevent overgrowth)
Preventing cattle grazing tick-infested areas during major risk periods
Applying topical products to control ticks, however when the effect of these
products wears off, the animal is once again susceptible to being bitten and
infected.
Prophylactic treatment of cattle about to be moved to a risk area
Effects of animal pests and diseases on productivity
Animal pests and diseases usually affect productivity negatively in ways listed
below:
Death of animals infected by deadly pathogens.
Pests (vectors) spread deadly pathogens and parasitic worms.
Parasites can cause anaemia through loss of blood hence disturbing the adequate
blood circulation that eventually leads to stunted growth.
Pathogens that destroy red blood cells disturb the normal transportation of oxygen
thus slowing down respiration that supplies energy to the body.
Physical damage to animals’ internal and external organs.
Ectoparasites such as ticks bite and damage the skin of animals causing wounds
that may be used by pathogens to infect the body.
Ticks and mites also suck blood from animals, which consequently leads to
anaemia.
Blood-sucking parasites also suck food nutrients meant for the animal, together
with the blood.
Pests and diseases reduce biomass and rate of growth (mass gain) of animals.
Reduction of milk or egg production is also a common consequence.
Increases the maintenance cost.
Ways of preventing animal pests and diseases
Dosing and deworming
Dosing means administering small quantities of chemicals or medicines orally
(through the mouth).
Deworming is treating an animal to free it of worms.
It is important to deworm livestock at regular basis so as to keep the herd worm-
free.
The most suitable time of deworming is the early stages of infection when the
worm load is less.
The local veterinary extension worker should be consulted suggestions regarding
deworming.
In adult animals deworming is done after examination of dung.
It is recommended to deworm adult females after giving birth not during gestation.
Young animals should preferably be dewormed every month.
Older stock can be dewormed at 4-6 months’ intervals.
In places of heavy endoparasite infestations (hot-humid regions) it is advisable to
deworm heifers twice a year up to two years of age.
Vaccination
Vaccination is a process of artificially stimulating immunity against specific
infectious diseases by injecting biological agents called vaccines in an animal’s
body.
Vaccine is a live attenuated (weakened) or dead form of a pathogen used to
stimulate immunity in animals.
The farm animals and young ones should be vaccinated at regular intervals at
appropriate times to be able to fight the infection in case of the real pathogen
invading the body.
Vaccination should be done with consultation of veterinary services.
Dipping
A dip is a construction that allows complete immerse of livestock in a liquid that
contains a parasiticide.
Dipping kills ectoparasites like ticks, mites and fleas on animal skin.
Plunge dips are fixed and made of concrete, typically for cattle.
Modern delivery forms such as pour-ons and injectables are also modern ways of
controlling ectoparasites.
Plunge dipping remains the most efficient and economic method for periodically
treating a very large number of animals against ectoparasites parasites.
Typical cattle dips have a volume of 10 000 litres or more.
Fig.5.1.5:
Cattle dipping to control ticks and mites
Quarantine
Quarantine is the segregation of apparently healthy animals that have been
exposed to the risk of infection from those animals that are healthy and not
exposed to the risk of infection.
The idea is to give sufficient time for any contagious disease that the quarantine
animals may be having, to become active and obvious.
The quarantine period depends on the incubation period of a disease but
practically a 30-day period covers most diseases.
During the quarantine period, animals should be thoroughly screened for parasitic
infestation by faecal examination and de-worming.
The animals should also be subjected to dipping to remove any ectoparasites.
