Lamb

Breeding of prime lambs

Type of Sheep @ Ruse

1 x Ram → Poll Dorset (No horns)

6 x Ewes → First Cross Ewes ([M] Merino [F] Border Leicester)

5 x Prime Lambs → ([M] First Cross Lamb [F] Poll Dorset)

Activities done during the year

• Foot/Hoof Paring

• General health checks – are carried out to ensure sheep are in good health

• Drench: Early November, Late December and Early February (only if it is necessary) alternating between Ivomec (a Broad Spectrum drench) and  a Narrow spectrum drench for Barber’s Pole worm and other roundworms. Particular attention is given to the sheep after lambing because the sheep are more susceptible to roundworms at this time.

• Weigh lambs periodically (monthly) to determine growth rate and when they have reached market weight (30 – 35 kg)

Breeding of prime lambs

Brucellosis is an infectious disease caused by bacteria from the genus brucella. It can affect various animals. Disease known as the Mediterranean region since antiquity.

Husbandry practices.

Sheep Husbandry Practices/Equipment

• Raddles, Used to control the rams

• 5 in 1 vaccinations, Intravenous, Subcutaneous, Oral

• Ear marking, Proof of ownership

• Ear tagging, for traceability and sheep id. PIC (Property identification code), NLIS (National livestock identification scheme)

• Budizzo, Crushes the testis and cuts off the blood flow

• Elastrator, Use elastic band to remove the testes.

• Testosterone, Increases muscle development

• Marking knife

• Hoof parers

• Drenching gun, Used for drenching the sheep, placed at the back of the mouth

Breeding

(Describe the breeding of a prime lamb)

Offspring from two different breeds benefit from hybrid vigour, which is where the offspring has superior qualities to both parents because of the greater genetic diversity. 

In Australia, a method of producing premium lamb is to utilise a double cross. This crossing program uses genetics from three of four groups of sheep to produce a lamb with maximum hybrid vigour. 

(cross used at JRAHS)

Notes:

• The pure breeds in the crossing program need to be kept as a separate flock

• The ratio of rams to ewe in breeding is 1:50-150

Characteristics 

• Merino ewes: common/easily accessible + good wool

• Border Leicester: a long wool breed

• First cross ewes: hybrid vigour (fast growing, very fertile, and produces a lot of quality milk to nourish fast growing lambs)

• Poll Dorset ram: short wool, bred for meat and a terminal sire (sires that produce the finished prime lambs)

Pests: Sheep Blowfly and Barber’s Pole Worm

(Describe for the Sheep Blowfly: life cycle, effects on sheep, control measures)

Life cycle

A female adult blowfly can lay 800-900 eggs in her lifetime

• 8-24 hours: Eggs hatch 

• Day 1: maggots are the size of a pinhead. (too) Hot weather and short wool may kill them.

• Day 2: the maggots have reached the final size of 1cm

• the maggots feed on the sheep until they pupate

• Day 6: they drop off to pupate in soil

• Day 12: flies emerge after 6 days in the early morning - in ideal moist conditions

The sheep blowfly is most active in high humidity and in 27ºc.

Effects on sheep

Symptoms

• Attraction of adult flies

• Observable maggots

• Fever and irritation

• Death of sheep

Control measures

To reduce flystrike in the flock choose sheep with

• dense fleeces

• plain bodies

DON’T breed sheep with conformation problems (e.g. swampy back or devil's grip)

• Mules all lambs in lamb marking time

• Mark correctly (too long or short tails increases chances of flystrike)

• Shearing and crutching should be carried out immediately before fly season

• Drench regularly (kills worms to stop scouring)

• Apply insecticides correctly

(Describe for Round Worms (e.g. Barber's Pole worm): life cycle, effects on sheep)

Life cycle

The adult female worm lays 5,000-10,000 eggs/day

Lifespan: 3 weeks

• eggs hatch as first stage larvae after 4-6 days (faeces)

• second stage larvae emerge from the cuticle (faeces)

• third stage larvae retain a protective cuticle and are infective (wet grass)

• the cuticle is shed as it travels through the stomachs (goat)

• they become fourth stage larvae within 48 hours. these penetrate the lining of the abomasum and feed. they are covered in a clot of blood. (abomasum)

• the worm matures into the adult stage after 3 days and emerges from the clot. they produce eggs after 2 weeks.

Symptoms

• anaemic - pale gums and part of the eye (conjunctiva)

• bottle jaw (a fluid swelling beneath the jaw.)

• weight loss or poor growth

• scouring/diarrhoea (if mixed worm burden)

Control measures

1. drench at recommended times

2. use grazing management to create low worm-risk paddocks

3. breed and feed for worm-resistant sheep

4. worm test at recommended times

5. manage drench resistance

Drenching

(Explain basic and strategic drenching)

Basic drenching is where a drench is routinely administered to sheep according to the calendar of operations. This produces a significant likelihood of the worm population developing resistance to the drench and the drench becoming ineffective.

With strategic drenching, a drench is used sparingly and in conjunction with other control methods.

Diseases: Brucellosis

(Describe for Brucellosis: causative organism, symptoms, means of spreading, control measures)

causative organism: 

the bacteria Brucella ovis

Symptoms:

• A reduction in lambing percentages

• Inflammation of the epididymis and scrotum 

(abnormalities of the testes)

It primarily affects rams - ewes usually only carry the infection for one or two oestrus cycles.

Means of spreading:

Movement of infected rams Rams spread in joining when they mate the same ewe, and between rams in the non-joining period. 

Introduced ewes could potentially spread, but this is less likely and can be managed by isolating non-pregnant ewes before joining. 

Control measures:

• Rams that have any clinical abnormalities or test positive for a blood test are culled.

• (antibiotics) streptomycin daily for 15 days

Rams are checked in the scrotum and epididymis (inflammation).

Vaccinations

(List the diseases controlled by 5-in-1 vaccine and explain how it works)

Prevents five clostridial diseases (enterotoxaemia (pulpy kidney), tetanus, black disease, malignant oedema and blackleg)

How it works:

• 1ml should be given at one time

• It should be administered under the skin (subcutaneous)

• stored in a fridge

Pathogen: disease-causing agent

Antigen: anything the body identifies as foreign or not part of itself, such as a bacteria or virus.

Antibody: a blood protein produced in response to and counteracting a specific antigen

Lamb Marking

(Explain how lamb marking is carried out and identify the equipment used)

Operation

Reason

Equipment

Process

Tail docking

A long tail collects faeces and urine, resulting in Flystrike.

Knife, cauterising iron or Elastrator + rubber Elastrator ring.

Removal of the tail below the third joint.

Castration 

Ram lambs not needed for breeding are castrated. Wethers are easier to look after - they are more placid and do not make the ewes pregnant.

Knife, bloodless emasculator or Elastrator + rubber Elastrator ring.

Elastrator (JRAHS):

A ring is stretched with Elastrator pliers and placed around the neck of the scrotum. Before the ring is placed both testicles must be below the ring.

Vaccination 

Lambs are vaccinated for the Cheesy gland and the Clostrididal diseases - enterotoxaemia (pulpy kidney disease), tetanus, black disease, malignant oedema (blackleg-like disease), and blackleg.(5 in 1 vaccine)

Vaccinating gun and machine.

Needle is inserted intra-muscularly (into a muscle)  in a bare patch such as the armpit of the lamb.

Ear marking

Identification - in NSW it is compulsory to cut the owner’s registered mark in the ear.

Ear-marking pliers.

The mark is cut in the right ear of ewes and the left of males.

Ear tagging

Identification - The National Livestock Identification System (NLIS) requires use of coloured tags with the owner’s brand embossed on them.

Ear tag pliers and ear tags.

The age tag is placed in the ear not containing the ear mark.

Mulesing 

Risk of Flystrike is significantly reduced.

Hand shears or cauterising knife.

Mulesing is the removal of skin wrinkles from the breech area of a Merino sheep. The aim is for the wound to scar and heal tightly and without wool. Healing takes about 4 weeks.

Crutching: removal of wool from around the tail and between the rear legs (for hygiene purposes).

Sex Hormones

(Explain the difference between a wether and a cryptorchid)

A wether has had his testes removed. This means a wether is infertile. He is no longer producing large quantities of testosterone and has no inclination for mating behaviour and less aggression.

A cryptorchid still retains his testes, but as the testes are held in the body cavity the sperm produced by the testes is infertile, so he cannot make a female pregnant. The testes are still producing testosterone so he has ram-like behaviour and growth characteristics.

(Describe the differences in the carcases of lambs that are ewes, wethers, and cryptorchids)

there is no difference in meat colour and tenderness.

Digestion

(Describe the structure and function of the parts of a ruminant digestive system)

Digestive system part

Structure 

Major function

Mouth, tongue and teeth

In the mouth, sheep have a hard dental pad on the upper jaw and teeth on the lower jaw

Swallows food

Oesophagus 

A long thin tube

Passes the food down

Rumen 

Large thick wall with papillae that increases the surface area

A fermentation chamber to digest the food. There are microorganisms (mainly bacteria and protozoa) that can break down food so they can digest grass.

Reticulum 

Honeycomb-like wall.

Aids the absorption of volatile fatty acids. 

Also sends food back to mouth if further chewing is required.

Omasum

A hard muscular organ. It has multiple leaves in its inner wall like a book.

Absorbs water.

Abomasum 

The lining is smooth and contains gastric planes 

also called ‘true stomach’.

The gastric planes secrete stomach acid (enzymes/gastric juices) which digest the food.

Pancreas 

Long flat gland

Produces enzymes that aid digestion (breaks down sugar).

Liver/gall bladder

The gall bladder is smaller than the liver

The liver produces bile which is stored in the gallbladder, which is released into the first section of the small intestine (duodenum).

Small intestine

A long organ shaped like a cord (25m long)

Most food nutrients are absorbed

Caecum 

A large comma shaped organ

Absorption of water (through the walls)

Large intestine

Large diameter organ (5m organ)

Dehydrates and stores stores fecal material

Rectum and anus

The rectum is a small chamber that is around 20cm long.

Stores fecal material.

(Define the term rumination)

The term rumination means the regurgitation of food from the rumen to the stomach for further chewing.

(Explain how digestion is carried out in ruminants)

Digestion in ruminants is carried out firstly by microorganisms in the rumen (bacteria, protozoa and fungi) and secondly by enzymes in the abomasum and small intestine.

(State that the ruminant animal is able to digest and utilise cellulose)

Cellulose is the main substance in the walls of plant cells, helping plants to remain stiff and upright. The cellulose molecule consists of hundreds – and sometimes even thousands – of carbon, hydrogen and oxygen atoms arranged into glucose units which form a long linear chain. The bonds that form between cellulose molecules give it strength. 

The human digestive system is unable to digest cellulose and it passes through the digestive system as fibre.

A ruminant animal such as a sheep is able to utilise dietary cellulose because microorganisms in the rumen and reticulum can break it down into the constituent glucose units. 

Nutrition

(Describe the feed sources for the school sheep)

James Ruse pasture is mostly a mix of kikuyu (grass) and white clover (legume). Sheep are also fed purchased lucerne hay to supplement the available pasture.

Grasses supply most of the carbohydrates (energy) to the animals.

With the help of specific rhizobium bacteria, legumes are able to convert atmospheric nitrogen to available nitrogen. Nitrogen is used to make protein, so legumes supply most of the protein needed by animals.

Meat Cuts and Consumption

(Identify most valuable parts of the carcase)

Generally the muscles of the back, loin and hind leg are the most valuable.

(Explain where the major cuts of lamb are found on a carcase diagram)

(Explain different methods of cooking meat)

• Dry heat methods: pan fry, stir fry, grill, BBQ and oven roast

• Moist heat methods (slow simmered): braised, stew, pot roast and casserole