Black''''s veterinary dictionary 21st edition - V pot

For example, sheep can be simultaneously immunised against pulpy kidney disease, lamb dysentery, braxy, blackleg, black disease, struck, Clostridium oede-matiens infection and tetanus b

A method of producing active immunity against

a specific infection by means of inoculation

with a vaccine, i.e a preparation of the necessary

antigen(s) (See IMMUNITY; IMMUNISATION;

IMMUNE RESPONSE; VACCINE.)

Vaccination in mammals is normally carried

out by inoculating individual animals The

method of administration depends on the type

of vaccine Most inactivated vaccines are

inject-ed intramuscularly or subcutaneously;

tempera-ture-sensitive live vaccines may be administered

as drops into the nasal passages; vaccines against

husk are given orally

Mass vaccination of poultry against Newcastle

disease may be achieved by dispersing aerosols of

vaccine over the heads of the birds with fine

spray pumps or adding vaccine to the drinking

water Some fish are vaccinated by dipping the

fish in a solution of the vaccine Fox populations

in Europe have been vaccinated against rabies by

impregnating chicken heads or other baits and

spreading them in known fox runs

Multiple-component vaccines containing antigens against

a number of diseases are available For example,

sheep can be simultaneously immunised against

pulpy kidney disease, lamb dysentery, braxy,

blackleg, black disease, struck, Clostridium

oede-matiens infection and tetanus by a single 8-in-1

vaccine

(In connection with foot-and-mouth disease,

see also RING VACCINATION.)

Vaccine

When an animal is inoculated with a vaccine as

protection against a specific disease, e.g

black-leg, this is carried out with the object of

stimu-lating production of antibodies in its system,

which will confer active immunity against

blackleg organisms

Vaccines may be prepared from live

organisms; from inactivated (killed)

micro-organisms; from genetically engineered subunits

of the pathogenic fraction of the organism;

or from toxoids – heat- or chemically-treated

micro-organisms that have lost their virulence

but retain their antigenicity, i.e ability to create

resistance to disease

Live vaccines are vaccines prepared from

bac-teria or viruses whose virulence is reduced by

heat, chemicals or passage through an animal

other than the normal host species For example,cattle plague vaccine may be prepared from the

virus passaged through (i.e grown in) chick

embryos Occasionally the live viruses used arerelated but non-pathogenic strains, usefulbecause they will stimulate antibody productionbut will not produce the disease

Viruses may be inactivated by phenol orultra-violet rays, for example; or they may bemodified in some way, such as by artificiallyinduced mutation, to produce a temperature-sensitive virus which will replicate in the nosebut not in the lungs Such a virus vaccine can beadministered by nasal spray

Tissue culture vaccines – live vaccines grown

on cell cultures – are used in the prevention ofcanine distemper, rabies, etc., and in treatment

of benign skin papillomata (warts) of cattle.Vaccines are sometimes used for treatment aswell as for prevention of a particular disease.X-irradiated worm larvae vaccine is used inthe prevention of PARASITIC BRONCHITIS

It is important that, in the commercial duction of live vaccines involving the use ofchicken embryos (or of tissue cultures derivedfrom them), contaminant viruses are eliminated.For example, the avian leukosis virus has conta-minated distemper vaccine and would represent

pro-a risk to vpro-accinpro-ated poultry if contpro-aminpro-ating vpro-ac-cines for them Scrapie was accidentally spread

vac-by an early louping-ill virus contaminated vac-by thescrapie agent

It is essential that vaccines are stored undersuitable conditions of temperature, etc.; thatthey are not used after the expiry date shown onthe package; that where 2 doses are stated to benecessary, both are given – and at the correctinterval Failure to observe these rules can meanthat the vaccinated animal does not become animmunised animal; it has led to dogs presumedproperly vaccinated against rabies becomingrabid after exposure to a natural infection (See also INJECTIONS;GENETIC ENGINEERING.)Inactivated vaccines are prepared from killedmicro-organisms that retain sufficient antigenicactivity to promote immunity They are not aspotent as live vaccines, and 2 doses at specifiedintervals are usually necessary to produce effec-tive immunity Inactivated vaccines often con-tain an adjuvant, usually an aluminium saltsuch as aluminium hydroxide, which enhancesthe immune reaction Some are water-based,others formulated in an oily medium Oil-based vaccines can cause serious reactions ifaccidentally self-injected into the operator.Leptospirosis vaccine is an example

Subunit vaccines are genetically engineered sothat only the antigenic fraction of a pathogen is

V

utilised The vaccine does not cause infection but

does stimulate immunity Feline leukaemia

vac-cine is an example; another is Aujeszky’s disease

vaccine The virus component of the subunit

vaccine has difficulty in penetrating the cells of

the vaccinated animal; it does not multiply well

within the cells and the animal does not shed the

virus By testing for the fraction missing from the

vaccinial strain of virus, a vaccinated animal can

be determined from one carrying the infection

Toxoid vaccines are produced by treating

tox-ins from micro-organisms so that their harmful

effects are removed but the antigenic properties

remain Tetanus vaccine is an example

Vaccinia Virus

This term may refer to the virus of naturally

occurring cow-pox, or to a strain which has

undergone mutation and was used for

vaccina-tion against smallpox (See POX.)

Vacuole

A cavity within a cell

Vacuum-Dipping of Eggs

A technique used in assisting the eradication

of Mycoplasma spp in poultry Fertile eggs are

dipped in a concentrated solutions of

antibiot-ic (usually tylosin) and subjected to a negative

pressure Some of the air in the egg’s air pocket

is thus extracted and about 0.5 ml of antibiotic

drawn through the shell into the egg and

absorbed This process is more effective in

help-ing to eliminate M gallisepticum than other

mycoplasmas

Vagina

The vagina extends from the cervix of the

uterus to the vulva Vaginal mucus is altered in

character during pregnancy, a fact which can be

made use of in pregnancy diagnosis (For

inflammation of the vagina, see VAGINITIS.)

An artificial vagina is used at AI centres for

the collection of semen

Vaginal prolapse in ewesThis may

pre-cede lambing by up to 55 days, but most cases

occur within the last 21 days of pregnancy

Ruptureof the vagina, with protrusion of the

intestine and rapid death, occurs not

uncom-monly in ewes of a large breed, of mature age,

carrying a twin – a week or two before lambing

is due Bulky foods – swedes, turnips, kale – are

often involved

Vaginoureteral fistula This has been

recorded in dogs and cats, as a complication of

ovariohysterectomy or a caesarean operation,and leads to urinary incontinence It has beensuggested that the fistula may occur followingaccidental ligation of the ureter during surgery,

or because the ureter becomes involved in

an inflammatory adhesion originating in thevaginal stump

Intermittent haemorrhage occasionallyoccurs in mares having very prominent varicoseveins at the dorsal aspect of the vulva-vaginalarea; it does not appear to affect health or fertil-ity Persistent vulval haemorrhage from varicoseveins of the dorsal wall of the vagina has alsobeen described It yields to local haemostatictreatment

Vaginitis

Inflammation of the vagina (See under ITY– Diseases of the genital organs in female;also ‘WHITES’; EPIDIDYMITIS – Epivag;VULVO- VAGINITIS,GRANULAR;PROLAPSE.)

INFERTIL-Vagotomy

Severing of the vagus nerve (See HYPERTROPHIC OSTEOPATHY.)

Vagus (Pneumogastric Nerve)

The vagus (pneumogastric nerve) is the 10thcranial nerve This nerve is remarkable for itsgreat length, and for the attachments which itforms with other nerves and with the sympa-thetic trunks It arises from the side of themedulla, passes out of the skull, and runs down

to the jugular furrow of the neck, where, alongwith the sympathetic, it accompanies thecarotid artery to the entrance to the chest Fromthis point the right and left vagi differ fromeach other in their course They both passthrough the chest cavity, giving branches to thepharynx (which run up the neck again), to theheart, bronchi, oesophagus, etc Each nervethen splits into 2 parts and the 2 upper branch-

es fuse with each other to form the dorsal trunk,the lower branches behaving similarly to formthe ventral trunk These 2 branches now passthrough the diaphragm, with the oesophagus,into the abdominal cavity, and end by givingbranches to the stomach, duodenum, liver, andvarious ganglia nearby (See Parasympathetic system under CENTRAL NERVOUS SYSTEM– Autonomic;also BRAIN.) (See GUTTURAL POUCH DISEASE.)

Valves are found in the heart, veins, lymph

ves-sels, etc., and serve the purpose of ensuring that

the fluids will only circulate in one direction

(See HEART;VEINS;ILEOCAECAL.)

Valvular Disease

(see HEART DISEASES)

Vampire Bats

Vampire bats are important transmitters of

rabies in parts of South and Central America,

the West Indies, etc The bat laps blood from

the wounds inflicted with its upper incisor teeth

on cattle, horses, etc In Mexico infected

vam-pires have made necessary the preventive

inocu-lation of 800,000 cattle a year Trypanosomiasis

can also be transmitted by vampire bats

Vampire bats imported into the UK remain in

quarantine for the rest of their life

Vanadium

A trace element essential in minute quantities

for the growth of chicks; as little as 10 mg/kg of

diet is an overdose that will suppress growth It

works with insulin to increase the amount of

glucose and aminoacids taken up by muscle

Varicose Veins

(see under VEINS)

Varied Diet, Need for

(see DIET AND DIETETICS; AMINO ACIDS; CAT

FOODS;DOGS’ DIET)

Varroasis

Varroasis is a parasitic disease of honey bees,

Apis melifera, caused by the mite Varroa soni The mite feeds on the developing larvae

jacob-and on the adult bees The result is weak beesand sometimes the death of the queen Wholehives can be wiped out, causing great economicloss not only to the apiculturalist but also tofruit and arable farmers; beekeepers often sup-ply hives to fruit growers and to fields of rapeand linseed Varroasis is prevalent in the UKand is a NOTIFIABLE DISEASE

As both parasite and host are arthropods,products used for control of the disease musthave a fine division between toxicity to the mite and toxicity to the bee Suspending stripsimpregnated with flumethrin or fluvalinate in thehive can be effective Other treatments includetobacco smoke or a vapourising block containingthymol and aromatic oils Eradication, however,

is difficult The disease came from Asia, where itdoes less harm because Asiatic bees groom eachother, thus removing the mites Long term, it hasbeen suggested that European and Asian beesmay be cross-bred to try to introduce the groom-ing habit into the European bee population Aleaflet available from DEFRA gives more details

of the disease and its control

Vas Deferens

(see under TESTICLE)

Vascular

Consisting of, or containing a high proportion

of, blood vessels

VasculitisInflammation of a blood vessel

Vasectomised

A male animal in which the vas deferens hasbeen cut Such an animal is sterile though itretains its libido and may be used for the detec-tion of oestrus (e.g in cattle) In breeding catter-ies one or two toms are sometimes vasectomisedfor the sake of peace, quiet and contentment ofqueens not being bred from until a later oestrus.Sterility does not immediately follow vasec-tomy (or castration), as some sperms will be inthe seminal vesicles and can lead to conception

Vasectomised 749

V

One-month-old foal with bilateral carpal valgus.

(With acknowledgements to Professor L C.

Vaughan and the Royal Veterinary College.)

after mating It may be 3 weeks or more before

the animal is sterile

Vasodilator

Anything which causes dilation of blood vessels

A drug used for this purpose is isoxuprine

hydrochloride (See NAVICULAR DISEASE.)

Vasomotor Nerves

Vasomotor nerves are the small nerve fibres that

lie in or upon the walls of the blood vessels and

connect the muscle fibres of the middle coat

with the nervous system By the continuous

action of the nerves the muscular walls of the

vessels are maintained in a moderate state of

contraction Any continuous and generalised

increase in this action results in a raising of the

blood pressure of the body, while a diminution

produces a lowering of the pressure Such

vaso-motor nerves are called vaso-constrictors, but

there are vaso-dilators as well The latter are

able to dilate the vessels, and cause either a

gen-eral or a local fall in the blood pressure, along

with an increased supply of blood to the part

Vasopressin

A hormone secreted by the posterior lobe of the

pituitary gland.It is also called ANTIDIURETIC

HORMONE(ADH) (See PITUITARY.)

Vector

The carrier which transmits a disease from one

animal to another For example, the mosquito

transmits malaria to man and a variety of diseases

to animals

Veins

With one or two exceptions, the veins lie

along-side or near to the corresponding arteries – thus

the renal vein brings back blood that has been

carried to the kidney by the renal artery and

lies alongside it The veins are, however, more

numerous and more irregular in their courses

than are the arteries, especially on the surface of

the body In regions, such as the cheeks, brain

meninges, and in the abdomen and thorax,

there are veins arranged quite irrespective of the

distribution of the arteries

StructureA vein is a thin-walled tube which

possesses a structure similar to that of an artery,

and consists of 3 coats, viz an outer fibrous,

a middle composed of muscular and elastic

fibres, and an inner coat composed of an elastic

membrane and flattened epithelial cells If an

ordinary vein is split open along its length,

there are seen to be a number of flap-like valves

attached to its inner surface These are like little

pockets, and are so arranged that they offer noresistance to the blood when it is flowing in the right direction, but prevent any back-flow.These valves are most numerous in the veins ofthe limbs, where gravity would naturally tend

to produce a back-flow, and least numerous inthe veins of the internal organs

Chief veinsThe arrangement and relations ofthe veins are very different in animals of varyingspecies, and even in different individuals, so thatonly a general description can be given here.Pulmonary veins – as many as 8 or 9 in thehorse and fewer in other animals – return theoxygenated blood from the lungs to the left auri-cle of the heart They possess no valves Openinginto the right auricle are 4 veins: (1) coronarysinus; (2) anterior vena cava; (3) posterior venacava; and (4) azygos vein The coronary sinus is

a short thick trunk that discharges the bloodused by the heart walls back into the general circulation The anterior vena cava drains theblood from the head, neck, 2 fore-limbs, andmuch of the chest wall It is formed by the con-fluence of the jugulars and the brachial veins,

750 Vasodilator

V

Valves of a vein showing pumping action of

adjacent muscles (Grollman, The Human Body, Macmillan Co., as used in R D Frandson, Anatomy

and Physiology of Farm Animals, Baillière, Tindall.)

and receives other branches from the neck,

vertebral region, and the chest wall The

posteri-or vena cava drains all the remainder of the body

except the region of the diaphragm, the

posteri-or intercostal areas, the oesophagus, and the

bronchial tubes, the blood from these parts

being collected into the azygos vein which joins

the right auricle separately in most animals The

posterior vena cava is formed under the lumbar

region by the union of the right and left

com-mon iliac veins, which drain the blood from the

pelvis and hind legs, and which are distributed

in a more or less similar manner to the

corre-sponding arteries of these parts From here it

passes forwards below the lumbar muscles in

company with the abdominal aorta, until at the

level of the last thoracic vertebra it passes

down-wards and fordown-wards, past the pancreas, and

reaches the liver

Its further course is partly embedded in the

liver substance until it arrives at a special

open-ing in the diaphragm, called the foramen venae

cavae, by which it gains the thoracic cavity

From here it passes along in a groove in the

right lung to reach the right auricle Its main

tributaries are as follows: (1) lumbar veins,

which empty blood from the lumbar muscles,

etc.; (2) internal spermatics in the male, and

utero-ovarian veins in the female, from the

generative organs in either sex; (3) 2 renal veins,

one from each kidney, satellites of the

corre-sponding arteries; (4) several large hepatic

veins, which return not only blood carried to

the liver by the hepatic arteries, but also that

which comes from the digestive organs by the

portal vein to undergo a second capillary

circu-lation in the liver (see PORTAL VEIN); and (5)

phrenic veins returning blood from the

diaphragm

In the venous system, even more so than

in the arterial system, there is an intricate

arrangement of anastomoses by which, when

one vein becomes damaged or diseased, lateral

branches from it may enlarge and carry away

the excess blood into other veins so that no

great hindrance to the return flow of the blood

to the heart may be occasioned If this were not

so, the circulation might be from impaired

minor causes

Veins, Diseases of

Those lying near to the surface are frequently

injured along with other tissues when contusions

or lacerations have been sustained, but so

exten-sive is their communication with neighbouring

veins that it is usually possible for these latter

to enlarge and undertake the functions of the

damaged vessels, and thereby prevent serious

consequences The deeper veins are protectedfrom all but the most severe, and usually fatal,injuries

Inflammation of a vein, or phlebitis, mayfollow the collection of blood samples whenunclean instruments have been used, or whenthe resulting skin wound has not received atten-tion In other cases it follows THROMBOSISandinfection

Varicose veinsare those which have becomestretched or dilated to an extent not justified bythe blood flow (See VARIOCELE and under VAGINA.)

Thrombosis of the posterior vena cava, whichmay follow abscess formation in the liver or else-where, is in cattle not infrequently followed bythe presence of clots in the pulmonary vessels,abscess formation and sometimes erosion of thepulmonary artery wall – giving rise to a fatalhaemorrhage Symptoms may include dullness,rapid breathing, a cough, chest pain, the pres-ence of blood in material coughed up, anaemia,and widespread rhonchi (See RECUMBENCY.)

Venereal Diseases

Animals, with the exception of the monkey, arenot subject to infection by the 2 great humanvenereal diseases of syphilis and gonorrhoea, butthere are several important contagious diseasesthat can be transmitted from animal to animal

by coitus These include brucellosis,

trichomoni-asis, Campylobacter fetus infection, and infectious

vaginitis of cattle, venereal granulomata or real tumours of dogs, and dourine or mal du coit

vene-of horses (See PROTOZOA;EPIDIDYMITIS; VAGINITIS, GRANULAR; CONTAGIOUS EQUINE METRITIS.)

VULVO-Venereal Tumours (Infective Granulomata)

Venereal tumours (infective granulomata) characterise a contagious disease of dogs

Signs In the female the original tumour is awarty excrescence which soon grows andbecomes cauliflower-like In advanced stagesthere is a large mass of pinkish or greyish-red tissue, which easily bleeds when touched, occu-pying the greater part of the vaginal passage and

Venereal Tumours (Infective Granulomata) 751

V

often causing a bulging and swelling of the

perineal region A dirty sticky blood-stained

dis-charge accompanies the condition, and the

ani-mal’s general health suffers In the male the

watery growths usually have a distinct stalk, and

are attached to the skin or mucous membrane of

the prepuce, or to the penis (See also under WARTS.)

Venezuelan Equine

Encephalomyelitis

A strain recognised in the 1930s A severe

out-break occurred in Venezuela and Colombia in

1962–4, when thousands of horses died and

about 30,000 people were infected A later

out-break spread to Mexico in 1970 where 6000

or more horses died, and then to Texas, USA

(See also EQUINE ENCEPHALITIS.)

Venom

(see SNAKES; TOADS; BUFOTALIN; SPIDERS;

SCORPIONS)

Vent Gleet

This condition in poultry is an inflammation

of the cloaca, with which is associated a thin

yellowish watery discharge which has a

charac-teristic and particularly unpleasant odour The

cloaca and adjacent skin appear swollen and

congested, and the bird exhibits signs of

irrita-tion Other birds attracted by the reddening of

the region may peck at vent; this leads on to

cannibalism

Egg production drops, and in some cases

egg-binding and impaction of the oviduct result

Culling is advisable There is a similar condition

in ducks but the material round the vent is more

solid This must be removed and the affected

area treated with antibiotic cream

Cases of severe infection of the eyes of

poultry-keepers treating this condition are not

uncommon

Ventilation

Ventilation may be summed up as ‘the measures

necessary to rectify the pollution of the air in a

building – without the production of a draught’

Whenever animals are enclosed in a confined

building they gradually use up the oxygen and

discharge into the air quantities of carbon dioxide

and water vapour, until, if no fresh air is supplied,

the percentage of oxygen decreases below the

amount required

One of the problems in livestock buildings

is condensation, which can lead to bronchitis

and pneumonia For buildings used for cattle

and sheep, provision of Yorkshire boarding is

one of the best and least expensive methods of

avoiding or curing condensation

Necessary air space

Cow, horse(Byre or stable) 5.6 200(Loose box or yard) 16.8–33.6 600–1200

Poultry(layers on slats) 0.17 6(layers on deep litter) 0.34 12The required amount of air for each animalmust be continuously brought in from the out-side, and an exit must be provided for an equalamount This is arranged for by the provision ofinlet and outlet ventilators

Inlets These include windows, direct inletpipes, perforated bricks and gratings, Yorkshireboarding, and electric fans

Windows, of which the Sheringham Valvetype is the most common and useful, serve thedual purpose of lighting and ventilation Those

on the lee side of a building serve as outlets whenthe wind is strong In the Sheringham Valvewindows, the incoming air is deflected upwards

by the hopper-like flap that falls inwards, so that

it is spread over a greater area than is the casewith other openings Inlet pipes are used, often

in conjunction with windows, to ensure a supply

of fresh air in the region of the animals’ heads

Ventilation rates – (maximum)

Changes

of air m3 ft3per hour per hour per hourBacon pig 20 5.7–34 200–1200Broiler chicken 40 6.8 240

OutletsThese include an open ridge, board ventilators, outlet shafts, open eaves,exhaust fans, and other devices The most satis-factory outlet is undoubtedly an open ridgealong the whole length of the building Theheated impure air rises and is drawn throughthe open space by the suction of the wind Thedisadvantages of this system are that the openspace will allow entrance to a certain amount ofrain or snow in bad weather; the system is alsoinapplicable to buildings possessing lofts

Poultry (adult) house 13 2

752 Venezuelan Equine Encephalomyelitis

V

Mechanical ventilators may be either of the

plenum or in-forcing type, or of the vacuum,

exhaust, or outforcing variety In the former a

larger power-driven fan is enclosed in a chamber

with communication to the outside of the

build-ing, and is connected by ducts or shafts with all

parts that are to be ventilated In the exhaust

variety one or more electric fans are enclosed in

turrets placed along the ridge of the roof

Ventilation tunnelThese have a fan to draw

air into the building and force it out through

vents over the stock

The temperaturein a livestock building is

a result of the heat released from the stock (for

example, a dairy cow gives off heat equivalent

to 0.5 kW; and with a heavy milker the figure

may be 1 kW) and the varying quantity of

ven-tilating air drawn from outside ‘Because

heat-ing and refrigeration are only economic for

young stock, the properties of the air entering

the building are those of the outside air and

vary considerably, depending on the weather In

hot weather a large amount of air is used, but in

cold weather only a small amount is required

and in many traditional systems this gives rise

to different patterns of internal air flow Bystudying the relevance of airflow patterns to theconditions near the stock and to the response

of the ventilation system the EnvironmentDepartment, NIAE, has designed a ventilationsystem which provides near uniform internalconditions as the outside temperature changes.The system ensures a desired airflow pattern byautomatically adjusting the inlet gap to main-tain an air speed of about 5 m/s Calculationsand experiments have shown that this systemwill maintain the required airflow pattern foroutside temperatures down to 0°C (32°F)

‘Another shortcoming of traditional systems

is the influence of wind on ventilation rates,particularly in cold weather when fans are running slowly For this reason the NIAE havediscarded the method of varying fan speed tocontrol rate of ventilation and recommendsswitching the fans on or off When fans are offthey are covered by simple backdraught shuttersand when on they are at full speed and so areleast affected by wind The fans are switched on

or off in predetermined steps and the inlet gap

is adjusted automatically to match the steps inventilation rate

‘The diagram [above] shows the essence ofthe system which has proved effective in fatten-ing piggeries, broiler houses and turkey build-ings and is fully described in the NIAE Report

No 28.’ (See also HOUSING OF ANIMALS;CARBON MONOXIDE)

Fan failure(For this and the resulting tality, see under CONTROLLED-ENVIRONMENT HOUSING.)

mor-Ventral

Ventral in anatomy indicates that a particularorgan or structure is situated towards theabdominal surface of the body, as distinct fromthe spinal or dorsal aspect

Ventilation methods for cattle houses: Top,

Chimney;Bottom, Continuous ridge outlet (With

acknowledgements to The UFAW Handbook on

Care and Management of Farm Animals, Churchill

Livingstone.)

A continuous heteroploid cell line derived from

African green monkey (Cercopithecus aethiops)

kidney tissue These cells are approved as a

sub-strate for the production of virus vaccines,

including rabies They are much easier to grow

than human diploid cells, and provide a better

yield; so that manufacturers are keen to use

them for vaccine production Latent virus inthese cells is a potential danger

Verotoxin

A total of 1012 milk filters were collected from

498 diary farms in south-west Ontario Thesupernatants of 20 (2 per cent) of the milk filtercultures had verocytotoxic activity Seven vero-

toxin-producing E coli strains were isolated, 2 of

which had been previously associated with disease

Covered with warts or vegetative growths In pigs

a verrucose endocarditis is recognised, the growth

being found on the heart valves The condition

may be associated with swine erysipelas or be

caused by staphylococci or streptococci

Version (Turning)

Version (turning) means the changing of a

pre-sentation at parturition so that some other part

of the fetus than that which was presented

orig-inally comes through the pelvic opening first

Vertebra

(see SPINAL COLUMN)

Vesicle (Small Blister)

A vesicle (small blister) is a collection of fluid in

the surface layers of the skin or of a mucous

membrane Vesicles are present in a number of

diseases, and according to their location, some

assistance is afforded for diagnostic purposes

For example, in foot-and-mouth disease the

vesi-cles are present in the mouth and on the feet,

while in cow-pox they are found on the teats,

udder, and other parts

Vesicles, Seminal

These secondary sex glands, like the prostate,

have openings into the urethra and are situated

close to the neck of the urinary bladder (See also

under SEMEN.)

Infected seminal vesicles can (rarely) cause

problems At a bull-rearing unit, 4 yearlings

appeared fit and well Their appetite was good

and they showed no signs of pain or discomfort

When, however, samples of their semen were

taken, clots of pus were noticed This finding

led to a careful examination of the bulls being

made, and it was then discovered that each had

a hard, painful swelling of one of their seminalvesicles Inflammation was found to be due to

infection with Actinobacillus actinoides Other

organisms sometimes involved include tubercle

bacilli, Brucella abortus, streptococci, and

Corynebactrerium pyogenes.

Vesicular Disease of Pigs

Vesicular disease of pigs is described underSWINE VESICULAR DISEASE (See also VESICULAR STOMATITIS.)

Vesicular Exanthema

A viral disease of pigs (and rarely of horses butnot of cattle) which has to be distinguished fromfoot-and-mouth disease It was eradicated fromthe USA in 1959 and has never been recordedelsewhere It is thought that the vesicular exan-thema virus may have been a ‘land variant’ ofthe San Miguel sea-lion virus, isolated from sea-lions off the coast of California

Vesicular Stomatitis

Vesicular stomatitis is caused by a rhabdovirustransmitted by mosquitoes and biting flies, andmay affect horses, cattle, pigs and, occasionally,sheep The blisters seen on the tongue haveoccasionally caused confusion with foot-and-mouth disease, and vice versa – with seriousconsequences Lesions can also occur on theudder or around the coronets It is a disease

of the summer, and mainly of the westernhemisphere, especially in the Caribbean area

In man the disease is influenza-like, withfever, sore throat, and several days’ malaise.Two strains of the virus are recognised – theNew Jersey and the Indiana Experimentally,

Vesicular Stomatitis 755

V

The NIAE ventilation system.

numerous mammalian species can be infected –

Veterinary degrees are conferred on graduates

from the veterinary faculties of Bristol,

Cambridge, Edinburgh, Glasgow, Liverpool

and London universities They lead to

member-ship of the Royal College of Veterinary

Surgeons (MRCVS) which allows the graduate

to practise in the UK as a veterinary surgeon

Higher degrees (PhD, MSc, etc.) are available

after postgraduate study, as well as certificates

and diplomas in specialist areas of veterinary

medicine and surgery Graduates of veterinary

schools in other EU countries may also become

MRCVS University degrees in veterinary

nurs-ing are also available

Veterinary Facilities on the

Farm

Every breeding cow and heifer in Britain has,

during its lifetime, to be caught, ear-tag read,

restrained and a blood sample taken from neck or

tail vein This will take place at least 2 or 3 times,

quite apart from any herd or individual

han-dlings necessary for clinical reasons or breeding

management Taking a blood sample can take as

little as 30 to 45 seconds given efficient holding

facilities; 200 cattle could be sampled in a

morn-ing’s work On most farms there is a lack of

cattle-handling facilities of the right type, so that

the catching of a single animal can and does take

all the farm staff about 20 minutes with the very

real possibility of broken gates and fences and

varying degrees of personal injury, even before

blood-sampling is attempted

Experience in the design and erection of

cat-tle handling units for dairy and beef catcat-tle has

shown the main points to be as follows:

Collecting pens should be large enough to

hold all stock to be handled, or all the stock

in units as they are housed, e.g 50s or 100s A

post-and-rail pen 9 ×18 m (30 ×60 ft) or 12 ×

13.5 m (40 ×45 ft) will hold 100 cows with

calves at foot A pen of 9 ×12 m (30 ×40 ft)

will hold 60 adult cattle or 80 young cattle

The forcing pen leads from the collecting pen

to the race or chute, and should be

funnel-shaped It should hold no fewer than 12 cows

plus calves, or 15 adult cattle – enough to provide

a group for handling without having repetitive

stops while 2s or 3s are run into the cow-race.The optimum dimensions are as shown in thediagram, and should not be made larger for largeunits The dimensions are those within whichcattle cannot evade pressure to go into the race byadopting a whirlpool movement

RaceAn 18 m (60 ft) long race, 680 mm (2 ft

3 in) wide internally and 1.680 m (5 ft 6 in) tothe top rail, will hold 10 to 12 cattle It should

be made up of verticals (sleepers) 2 m (6 ft 6 in)between centres sunk 900 mm (3 ft) into theground, the bottom concreted with a brushedsurface There should be 4 horizontal rails.Height above ground of the 2nd and 3rd rails isspecific in that it accommodates the large, fat orpregnant animal

Catwalk and working space Catwalksshould be provided on both sides of the cowrace, 760 mm (2 ft 6 in) above ground level andnot less than 300 mm (12 in) wide, in wood.Space should always be provided for 2 catwalks,even when building in close proximity to anexisting wall – i.e the face should be stood offfrom the wall, however tempting it may be to use

an existing wall for one side Cattle can then berun in either direction for procedures on eitherflank (vaccinations, branding, testing, etc.)

Crush and veterinary gatesThe crushshould be stood off 1.079 m (3 ft 6 in) from theend of the cow race with the same internalwidth of 680 mm (2 ft 3 in), and suitable gates

to hold animal No 1 firmly, stop animal No 1from backing out of crush before being heldand prevent animal No 2 from pushing up Thematerials and sizes are the same as for the race

Yoke or headstockA device for restrainingcattle by the neck, strongly made from wood ormetal and designed so that the head cannot jerkabout While securing the animal firmly, itincorporates a quick-release frame to free it in