Sheep (Leaving Cert Agricultural Science): Revision Notes

Sheep

Understanding sheep production is fundamental to Irish agriculture, where sheep farming plays a vital role in both mountain and lowland farming systems. This topic covers essential terminology, breed characteristics, farming methods, breeding strategies, and management practices that every Agricultural Science student should master.

Basic terminology

Before diving into breeds and production systems, it's essential to understand the key terms used in sheep farming. These terms describe sheep at different life stages and their roles in breeding programmes. Mastering this terminology forms the foundation for understanding all aspects of sheep production.

Life stages and classifications:

• Lamb - A young sheep under one year of age, representing the newest generation in the flock
• Hogget - A yearling sheep that is approximately one year old, transitioning from juvenile to adult
• Ewe - An adult female sheep used for breeding and milk production
• Ram - An intact adult male sheep used for breeding purposes
• Wether - A castrated male sheep, typically raised for meat production rather than breeding

Key breeding terminology:

• Prolific - Describes breeds that consistently produce multiple offspring, such as twins or triplets, in a single birthing cycle
• Sire - The male parent of an animal, contributing half the genetic material to offspring
• Dam - The female parent of an animal, also contributing half the genetic material to offspring
• Terminal sire - A ram specifically chosen to produce fast-growing, high-quality offspring destined for slaughter
• Maternal sire - A ram selected to produce daughters with excellent genetic traits, particularly good milk production and mothering ability, with these daughters often becoming replacement breeding ewes
• Carcase - The dressed body of a slaughtered animal after removal of head, feet, and internal organs
• Cast or draught ewe - An older ewe whose fertility has declined due to harsh environmental conditions, typically sold from mountain farms to lowland operations for breeding

Mountain and hill sheep breeds

Mountain and hill farming represents an extensive system where sheep must survive in challenging environments. The breeds selected for these conditions prioritise hardiness and survival over maximum production.

Blackface Mountain This hardy breed thrives in Ireland's mountainous regions, adapted to harsh weather conditions and rough terrain. These sheep can graze on poor-quality pasture and survive with minimal intervention from farmers.

Wicklow Cheviot Another mountain breed well-suited to upland conditions, the Wicklow Cheviot demonstrates excellent survival instincts and can maintain condition on sparse vegetation typical of hill farming areas.

Lowland sheep breeds

Lowland farming systems support more intensive production, allowing farmers to select breeds that prioritise productivity and prolificacy over pure survival traits.

Border Leicester

• Distinctive white colouring makes identification easy in mixed flocks
• Large frame size indicates good growth potential and meat production capacity
• Polled characteristic (naturally hornless) reduces injury risks and management complications
• Long wool provides valuable fleece production alongside meat
• Upright ears suggest alertness and good health
• High prolificacy means regular production of twins and triplets

Galway Sheep Ireland's only native breed holds special significance in the country's agricultural heritage:

• Pure white appearance creates uniform flock appearance
• Large body size supports good meat production
• Polled nature reduces handling difficulties
• Long wool contributes to fleece value
• Adapted specifically to Irish climate and farming conditions

Belclare Improver This modern breed represents successful selective breeding programmes:

• Developed through careful cross-breeding of Galway sheep with other prolific breeds
• Extremely prolific, consistently producing multiple lambs
• White colouring maintains breed uniformity
• Excellent mothering instincts ensure high lamb survival rates
• Polled characteristics reduce management challenges
• Minimal lambing difficulties reduce veterinary costs and labour requirements

Ram breeds

Specialist ram breeds serve specific purposes in commercial sheep production, particularly in terminal crossing programmes designed to produce high-quality meat animals.

Suffolk and Texel represent the two most important terminal sire breeds used in Irish sheep farming. These rams impart rapid growth rates and excellent meat conformation to their offspring, making them ideal for producing lambs destined for slaughter rather than breeding.

Types of sheep farming systems

Irish sheep farming operates through two distinct systems, each adapted to specific geographical and economic conditions. Understanding these systems is crucial for matching breeds and management practices to environmental constraints.

Mountain and hill farming characteristics:

• Extensive management system with large areas of land per animal
• Lower production targets due to environmental constraints
• Rough grazing on natural grassland and heather
• Ewes typically produce single lambs due to nutritional limitations
• Higher ewe and lamb mortality rates due to harsh conditions
• Lower input costs but also lower output per animal

Lowland farming characteristics:

• Intensive management with higher animal density
• High production targets maximising output per hectare
• Rotational grazing on improved pastures with fertilisation
• Ewes regularly produce twins or triplets through better nutrition
• Lower mortality rates due to improved conditions and veterinary care
• Higher input costs but significantly greater returns

Reproductive cycle of sheep

Understanding the reproductive cycle is essential for managing breeding programmes effectively.

• Sheep are seasonal breeders (short-day breeders), meaning they breed in autumn when daylight decreases
• The oestrous cycle lasts approximately 17 days
• Signs of heat include restlessness and standing to be mounted by the ram
• Gestation period is approximately 147 days
• Flushing involves increasing ewe nutrition before mating to improve ovulation rate and increase chances of twins

Lambing management

Lambing is a critical stage in sheep production that directly affects flock productivity.

• Signs of lambing include restlessness, isolation, and swelling of the udder
• Stages of lambing:
  • Dilation of cervix
  • Delivery of lamb
  • Expulsion of afterbirth
• Care of newborn lambs:
  • Clear mucus from nose and mouth
  • Dip navel in iodine to prevent infection
  • Ensure intake of colostrum within first few hours
• Common problems:
  • Difficult birth (dystocia)
  • Weak or chilled lambs

Nutrition and feeding

Nutrition is a key factor influencing sheep productivity and health.

• Sheep are primarily grass-fed animals in Ireland
• Lowland systems use rotational grazing on improved pasture
• Winter feeding includes silage and concentrates
• Flushing ewes before mating improves prolificacy
• Late pregnancy feeding is critical to prevent weak lambs
• Mineral supplementation (e.g. lick blocks) prevents deficiencies

Sheep health and disease

Maintaining flock health is essential for productivity and profitability.

• Internal parasites (worms) reduce growth rates and cause weight loss
• Liver fluke affects liver function and reduces productivity
• Foot rot causes lameness and reduced grazing ability
• Vaccination programmes protect against common diseases
• Dosing (use of anthelmintics) controls parasite burdens

Production cycle of sheep

The sheep production cycle follows a yearly pattern:

• Mating (autumn)
• Gestation (~147 days)
• Lambing (spring)
• Rearing lambs
• Weaning
• Finishing lambs for market
• Slaughter

Prolificacy calculations

Prolificacy measures reproductive efficiency in sheep flocks, calculated as the number of lambs successfully reared per ewe mated. This calculation helps farmers assess breeding programme success and make informed decisions about flock management.

Prolificacy typically passes from ram to offspring, making ram selection crucial for improving flock productivity. A prolificacy rate above 1.5 is considered excellent performance in commercial sheep farming.

Kill out percentage

Understanding carcase yields helps farmers evaluate the commercial value of their livestock and make informed marketing decisions. This measurement is essential for comparing different breeds and feeding systems.

Commonage systems

Commonage represents a traditional land use system still practised in parts of Ireland, particularly in mountainous regions like County Kildare's Curragh. Under this system, two or more farmers share grazing rights on the same piece of land, requiring cooperation and agreed management practices to prevent overgrazing and maintain land quality.

Selecting breeding stock

Making informed decisions when purchasing sheep requires careful evaluation of multiple factors that influence both immediate productivity and long-term genetic improvement. Poor selection decisions can affect flock performance for many years.

Criteria for buying ewes:

• Age - Young ewes offer longer productive life but may lack proven performance records
• General health - Visual assessment for signs of disease or parasites
• Body condition - Target Body Condition Score (BCS) of 3.5 at mating ensures adequate nutrition reserves
• Conformation - Good structural soundness affects longevity and mobility
• Prolificacy history - Evidence of consistent multiple births increases flock productivity
• Physical soundness - Healthy mouth, teeth, and feet essential for grazing and mobility
• Udder quality - Two functioning teats without lumps or discharge ensure adequate milk supply for lambs

Criteria for buying rams:

• Breed type - Always specify breed examples in examinations to demonstrate understanding
• Pedigree and performance testing - Genetic records indicate potential for passing desirable traits
• Age considerations - Balance experience with remaining productive life
• Conformation - Structural correctness affects mating ability and longevity
• Body condition - BCS of 4 at mating ensures breeding soundness
• Physical examination - Sound feet, legs, and mouth essential for mobility and feeding
• Testicular health - Firm, uniform testicles free from lumps indicate fertility (larger testicles generally correlate with increased semen production)

Breeding strategies

Understanding different breeding approaches allows farmers to select strategies that match their production goals, environmental conditions, and market requirements.

Mountain and hill farming approach: Mountain farming maintains breed purity by crossing pure-bred ewes exclusively with pure-bred rams of the same breed. However, the fertility of mountain ewes typically declines after several years due to harsh environmental conditions. These cast ewes are then sold to lowland farmers for continued breeding under more favourable conditions.

Lowland crossbreeding strategies: Lowland farming employs sophisticated crossbreeding programmes to maximise hybrid vigour and production efficiency. Cast mountain ewes are mated with rams from highly prolific breeds, producing crossbred offspring known as "grey-face" sheep due to their mixed colouring.

These crossbred ewes demonstrate hybrid vigour, combining the best characteristics of both parent breeds. They are subsequently mated with either Suffolk or Texel rams depending on market requirements:

• Suffolk crosses produce fast-growing lambs ready for the Easter market (early lamb production)
• Texel crosses develop more slowly, targeting mid-season markets rather than premium early sales

Benefits of crossbreeding in lowland systems

The use of crossbred ewes in lowland sheep farming delivers multiple advantages that justify the more complex breeding programmes. These benefits demonstrate why most commercial operations have moved away from purebred systems.

• Increased hybrid vigour - Crossbred animals often outperform their purebred parents in growth rate, disease resistance, and overall productivity
• Superior mothering ability - Crossbred ewes typically demonstrate better maternal instincts and milk production
• Enhanced carcase quality - Improved meat-to-bone ratios and better muscle development
• Higher prolificacy - Increased likelihood of multiple births per breeding cycle
• Improved milk production - Better nutrition for lambs leading to faster growth rates

Economic and sustainability considerations

Modern sheep farming must balance profitability with environmental responsibility.

• Profitability factors:
  • Lamb price and market timing (e.g. Easter lamb commands premium price)
  • Feed and input costs
  • Mortality rates
  • Stocking density
• Sustainability:
  • Sheep help maintain upland landscapes
  • Risk of overgrazing if poorly managed
  • Contribution to greenhouse gas emissions
  • Role in maintaining biodiversity