Course Content
Agriculture Form 1 Topics
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Unit 1 : Natural Resources
Unit 2 : Agricultural Research
Unit 3 : Agricultural Technology
Unit 4 : Proper Use of Farm Structures
Unit 5: Farm Business Management
Unit 6 : Agricultural Marketing and Food Security
Unit 7 : Agro-Based Industries
Unit 8: Food Distribution
Unit 9a : ESSENTIAL PLANT NUTRIENTS
Unit 9b :Functions, sources & causes of depletion
Unit 9c :Deficiency signs for each essential plant nutrient
Unit 10 :Vegetable Growing
Unit 11 :Classes of Livestock
Unit 12:Chicken Production
Unit 12b: Diseases and Parasites of Chickens
Form 1 Agriculture Lessons for JCE: Grow Your Knowledge

Classes of Livestock

1. Classification of Livestock

Livestock are broadly classified into two main groups based on their digestive system:

  • Ruminant (Polygastric) Animals: Animals that possess a four-chambered stomach and partially digest food, regurgitate it as cud for re-chewing, and then re-swallow it.1 The process of re-chewing cud is called ruminating.
     
    • Examples: Cattle, Goats, Sheep.2
       
  • Non-Ruminant (Monogastric) Animals: Animals with a single-chambered stomach.3
     
    • Examples: Pig, Birds. (Note: Horses and rabbits are non-ruminants but can digest cellulose due to a large, functional caecum).4
       

2. Distinguishing Ruminants from Non-Ruminants

Feature Ruminant Animals Non-Ruminant Animals
Stomach Chambers Four (polygastric) One (monogastric)
Cud Chewing Chew cud (ruminate) Do not chew cud (do not ruminate)
Cellulose Digestion Digest cellulose (due to microorganisms in rumen) Do not digest cellulose (except horse/rabbit due to caecum)
Chemical Digestion in Mouth No chemical digestion; saliva only softens/lubricates Chemical digestion may occur (e.g., salivary amylase in some species)

Similarities:

  • Water absorption occurs in the colon in both.
  • The final stage of protein digestion occurs in the small intestines in both.

3. Functions of Digestive System Parts (Ruminants)

Understanding the digestive system helps in choosing appropriate feed.

  • Mouth: Chews and swallows food. Saliva softens and lubricates; no chemical digestion.
  • Oesophagus: Muscular tube for food movement.
    • Peristalsis: Food movement from mouth to stomach.
    • Antiperistalsis: Partially digested food movement from stomach (rumen) back to mouth for re-chewing.
  • Stomach Chambers (Four):
    • 1st – Rumen (Paunch/Sack): Largest compartment.
      • Temporarily stores food during grazing.
      • Muscular contractions churn and mix feed with digestive juices and microorganisms (bacteria, protozoa).
      • Sends fine particles to reticulum; sends coarse, partially digested feed back to mouth for re-chewing.
      • Benefits of Microorganisms: Break down cellulose, synthesize proteins (reducing need for protein-rich feeds), digest fats, synthesize vitamins K and B.
      • Benefits to Microorganisms: Suitable environment, food from host.
    • 2nd – Reticulum (Honeycomb): Receives fine/digested particles from the rumen.
    • 3rd – Omasum (Bible): Many compartments for large surface area.5
       
      • Main function: Squeezes and absorbs water from food into bloodstream.
    • 4th – Abomasum (True Stomach):6
       
      • Muscular walls churn feed, mixing with gastric juice to form chyme.
      • Chemical digestion of protein by enzymes (pepsin, rennin).
      • Contains hydrochloric acid (HCl) secreted by gastric glands.7
         
        • Functions of HCl: Kills harmful microorganisms, provides acidic medium for pepsin.
  • Small Intestines:
    • Duodenum: Digestion of proteins by pancreatic juice; proteins further broken down into amino acids.
    • Ileum: Absorption of fully digested products into the bloodstream.
  • Large Intestines: No digestion occurs; primary function is water absorption into the bloodstream.

4. Digestive System Differences Among Non-Ruminants

Non-ruminants have a single-chambered stomach.8

  • Pig: Has a simple monogastric digestive system.
  • Birds: Have unique structures like a crop (for food storage) and gizzard (for grinding food) in addition to a simple stomach.9
     
  • Horse and Rabbit: While non-ruminants, they can digest cellulose effectively.10 This is because they possess a large and functional caecum that houses microorganisms capable of breaking down cellulose. This adaptation allows them to graze on fibrous material.
     

 

Digestion in Pigs and Chickens

This section details the digestive processes in two key non-ruminant livestock: pigs and chickens.

1. Digestion in Pigs

Pigs have a monogastric (single-chambered) digestive system.

  • Mouth: Feed is mixed with saliva. (Note: No chemical digestion by ptyalin mentioned here, unlike some other monogastrics).
  • Stomach:
    • Produces gastric juice containing hydrochloric acid (HCl) and enzymes pepsin and renin.
    • Pepsin: Breaks down proteins into smaller molecules called peptides.
    • Renin: Digests milk protein specifically in piglets.
    • Hydrochloric Acid (HCl) Functions:
      • Kills harmful microorganisms in food.
      • Provides an acidic medium for pepsin enzyme function.
      • Dissolves hard substances like bones.
  • Small Intestines:
    • Duodenum:
      • Pancreatic juice (from pancreas) contains trypsin (digests proteins), lipase (digests fats), and amylase (digests carbohydrates into maltose).
      • Bile (from gall bladder) emulsifies fats (breaks them into smaller globules) to aid lipase action.
    • Ileum:
      • Intestinal walls secrete intestinal juice containing enzymes:
        • Peptidase: Completes digestion of peptides into amino acids.
        • Lipase: Completes digestion of lipids into fatty acids and glycerol.
        • Maltase: Completes digestion of maltose into glucose.
      • Functions: Completes digestion and absorbs end products (glucose, amino acids, fatty acids/glycerol) into the bloodstream via villi.
  • Large Intestines (Colon):
    • Caecum: Contains microorganisms that digest cellulose.
    • Large Intestines: Absorb water from indigestible food.
  • Rectum: Temporarily stores stools before excretion.

2. Digestive System of a Chicken

Chickens have a unique digestive system adapted for consuming grains and other feeds.

Part Description Functions
Beak Bone-like structure; grows if cut. Picks up food; breaks food into smaller sizes.
Mouth No teeth; pointed tongue with taste buds; saliva lacks salivary amylase. Tongue helps in selecting feeds (taste buds) and swallowing.
Upper Oesophagus Tube. Passage of feed from mouth to crop.
Crop Enlargement of the oesophagus. Stores and moistens feed, preparing it for physical digestion.
Lower Oesophagus Connects crop and proventriculus; more swollen. Passage of feed from the crop to the proventriculus.
Proventriculus True stomach. Produces gastric juice (water, hydrochloric acid, and enzymes) which primarily digests protein.
Ventriculus (Gizzard) Thick, muscular wall with rough lining; contains grit (sand). With the help of grit and rough lining, it grinds feed into small particles (mechanical digestion).
Small Intestines Made of duodenum and ileum. Site of chemical digestion and absorption of nutrients.
Caecum Two branched blind sacs. Contain microorganisms that digest cellulose.
Colon (Large Intestine) Large intestine. Absorption of water from indigestible feed.
Cloaca Common opening for urinary, digestive, and reproductive systems. Passage through which faeces and urine are passed out.
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