Meat Science I – SS3 Livestock Farming Lesson Note (Second Term)

Meat science is the study of how an animal is converted into food in a professional and hygienic way, from resting the animal to chilling the carcass.

Behavioural objectives

By the end of the lesson, students should be able to:

1. define a carcass and state the aim of a good abattoir;
2. explain why animals are rested and given water but no food before slaughter;
3. list the steps of the slaughtering process in order;
4. describe the four activities in carcass dressing;
5. explain why a carcass must be chilled soon after dressing.

What is a carcass?

A carcass is the body of a slaughtered animal after the head, feet and internal organs have been removed.

• Abattoir (slaughterhouse): a place built for slaughtering animals and preparing meat hygienically.
• Slaughter slab: a simple local place where animals are slaughtered, common in many Nigerian towns and villages.
• Aim of a good abattoir: to produce a carcass in the cleanest way possible.
• Offal: the internal organs and other parts removed from the carcass, such as stomach, intestines, liver and lungs.
• Result of poor handling: the meat is tough, spoils quickly and can make people sick.

How should animals be handled before slaughter?

Animals should be rested in a holding area called the lairage for 12 to 24 hours before slaughter.

• Lairage: the shaded pen where animals wait and rest before slaughter.
• Clean water: animals must have plenty of clean water during the rest period.
• No food: animals are not fed before slaughter.
• Why no food? An empty stomach is easier to remove without cutting it and spilling waste onto the meat.
• Why rest? A stressed animal has tired muscles, so the meat is dark, dry and spoils quickly.
• Result of rest: a relaxed animal gives bright, juicy meat.

Why must animals and carcasses be inspected?

Meat inspection is the checking of animals and carcasses by a veterinary officer to make sure the meat is safe to eat.

• Before slaughter (ante-mortem): the live animal is checked for signs of illness, and sick animals are kept out.
• After slaughter (post-mortem): the carcass and organs are checked for signs of disease.
• Purpose: only healthy meat reaches buyers, which protects their health.

What are the steps in the slaughtering process?

There are four steps in slaughtering: stunning, bleeding, skinning or scalding, and evisceration.

1. Stunning (optional, modern): the animal is made unconscious so that it does not feel pain.
2. Bleeding (exsanguination): a very sharp knife cuts the jugular veins in the neck.
   • As much blood as possible must drain out.
   • Blood spoils very fast, so blood left in the meat makes it spoil quickly.
3. Skinning or scalding:
   • Skinning: the skin (hide) of cattle, sheep and goats is carefully peeled off.
   • Scalding: pigs are usually dipped in hot water to remove the hair while the skin stays on.
4. Evisceration (the clean-out): the stomach, intestines, liver and lungs are removed.
   • This is the most delicate step.
   • The intestines must not be punctured, because the waste inside carries bacteria that ruin the meat.

What is carcass dressing?

Carcass dressing is the preparation of the carcass for the butcher’s shop after the internal organs are removed.

• Trimming: excess fat, bruised meat and dirty parts are cut away.
• Splitting: a large carcass, such as a cow, is cut down the backbone into two sides for easy handling and cooling.
• Washing: clean, pressurised water removes remaining blood and bone dust.
• Weighing: the dressed weight is recorded to compare with the live weight of the animal.

How is dressing percentage worked out?

• Formula: dressing percentage = (dressed weight ÷ live weight) × 100.
• Example: an animal of 200 kg live weight gives a 100 kg carcass, so the dressing percentage is 50%.

Why must a carcass be chilled after dressing?

Chilling is the cooling of the dressed carcass to about 1°C to 4°C in a chiller or very cool room to slow the growth of bacteria.

• Warm meat: fresh meat is warm, and bacteria multiply quickly in warm meat.
• Cold chain: keeping the meat cold from the abattoir to the buyer.
• Firm meat: chilling firms the meat, so it is easier to cut into steaks or chunks later.
• Freshness: chilled meat stays fresh for days.
• No chiller: slaughter in the cool early morning, keep the meat shaded and clean, and sell it quickly.

What is the full order of meat handling?

Meat handling has seven stages, from resting the live animal to chilling the carcass.

What makes a good slaughter?

A good slaughter follows clean, quick and organised practices, as shown below.

Evaluation

1. Define a carcass and state the aim of a good abattoir.
2. Why are animals given water but no food before slaughter?
3. At a local slaughter slab, are the waiting animals resting in the shade with water or standing in the hot sun? How will this affect the meat?
4. Why does a veterinary officer inspect the animal before it is killed and the organs after it is killed?
5. In a village with no electricity or chiller, what is the best time of day to slaughter so the meat stays fresh for buyers?

Assignment

Write a short note on the handling of meat after slaughter, covering these three points:

1. List the four steps of the slaughtering process in order.
2. Explain why blood must be removed properly from the carcass.
3. State the four activities in carcass dressing and say what each one does.