Unit5 - Subjective Questions

The ruminant stomach is a compound stomach consisting of four distinct compartments. These allow ruminants to digest fibrous plant material effectively.

1. Rumen (Paunch):

• Structure: The largest compartment, acting as a large fermentation vat. It contains strong muscular pillars and is lined with papillae to increase surface area.
• Function:
  • Fermentation: House billions of bacteria, protozoa, and fungi that break down cellulose and hemicellulose.
  • Synthesis: Microbial synthesis of Volatile Fatty Acids (VFAs), Vitamin B-complex, and microbial protein.
  • Absorption: Absorption of VFAs (Acetate, Propionate, Butyrate) through the papillae.

2. Reticulum (Honeycomb):

• Structure: Lined with honeycomb-like ridges. It is contiguous with the rumen.
• Function:
  • Sorting: Acts as a pacemaker for rumen contractions and helps separate fine particles from coarse ones.
  • Regurgitation: Initiates the regurgitation of bolus for rumination (cud-chewing).
  • Hardware Stomach: Heavy foreign objects (nails, wire) often settle here, potentially causing 'Hardware Disease'.

3. Omasum (Manyplies):

• Structure: Spherical organ filled with muscular laminae (leaves) studded with papillae.
• Function:
  • Water Absorption: The primary site for water absorption (recycling fluid).
  • Particle Reduction: Grinds food particles further between the leaves.

4. Abomasum (True Stomach):

• Structure: The glandular stomach, similar to the stomach of monogastric animals.
• Function:
  • Enzymatic Digestion: Secretes hydrochloric acid (HCl) and digestive enzymes (pepsin, rennin).
  • Protein Digestion: Digestion of microbial protein and bypass protein begins here before passing to the small intestine.

Poultry (birds) have a simple stomach (monogastric) but possess specialized organs to handle food since they lack teeth for mastication.

1. Crop (Ingluvies):

• Location: An outpouching of the esophagus at the base of the neck.
• Function:
  • Storage: Acts as a temporary storage reservoir for feed, allowing the bird to eat quickly and digest later.
  • Moistening: Feed is moistened and softened by mucus secretions.
  • Fermentation: Slight bacterial fermentation occurs here, producing some organic acids.

2. Proventriculus (Glandular Stomach):

• Location: Situated before the gizzard; it is the 'true stomach' of the bird.
• Function:
  • Secretions: The glandular lining secretes gastric juices containing Hydrochloric acid (HCl) and Pepsin.
  • Passage: Food passes through quickly; chemical digestion initiates here but mainly takes place in the gizzard and small intestine.

3. Gizzard (Ventriculus/Muscular Stomach):

• Location: Follows the proventriculus.
• Structure: Thick, powerful muscular walls lined with a tough, keratinized layer (koilin layer).
• Function:
  • Mechanical Grinding: Acts as the bird's 'teeth'. Strong muscular contractions grind coarse feed particles.
  • Grit Utilization: Birds often consume small stones (grit) which lodge here to aid in grinding grains and fibers.
  • Mixing: Mixes the feed with the digestive enzymes secreted by the proventriculus.

Feedstuffs are broadly classified based on fiber content and nutrient density (TDN - Total Digestible Nutrients) into Roughages and Concentrates.

The Proximate Principles of Feed refer to the broad classification of nutrient components in feedstuffs as determined by the Weende System of Analysis (developed in 1860). It partitions the feed into six fractions:

1. Moisture (Water): Determined by drying the sample at until constant weight is achieved. The loss in weight represents water.

2. Dry Matter (DM): The residue remaining after removing moisture. It contains all the nutrients.
   

3. Crude Protein (CP): Determined by the Kjeldahl method, which measures total Nitrogen (). Since proteins contain approx. 16% nitrogen:
   

   
   Note: It includes true protein and Non-Protein Nitrogen (NPN).

4. Ether Extract (EE): Also called Crude Fat. Determined by extracting the dry sample with ether. It represents fats, oils, waxes, and fat-soluble vitamins. Fat provides 2.25 times more energy than carbohydrates.

5. Crude Fiber (CF): Represents the structural carbohydrates (cellulose, hemicellulose, lignin). It is the residue left after boiling the sample in weak acid and weak alkali.

6. Total Ash (Mineral Matter): The residue left after burning the sample at . It represents inorganic minerals.

7. Nitrogen Free Extract (NFE): Calculated by difference. It represents soluble carbohydrates like starch and sugars.
   

Carbohydrates are the primary source of energy in livestock rations, constituting 70-80% of the dry matter in plant-based feeds.

Classification:

1. Soluble Carbohydrates (Non-Structural):
   • Found inside the plant cell.
   • Examples: Sugars (Glucose, Sucrose) and Starch.
   • Represented as Nitrogen Free Extract (NFE) in proximate analysis.
   • Highly digestible.
2. Structural Carbohydrates (Fibrous):
   • Found in the plant cell wall.
   • Examples: Cellulose, Hemicellulose, and Lignin (indigestible).
   • Represented as Crude Fiber (CF).
   • Less digestible, requires microbial fermentation.

Significance in Ruminant Nutrition:

• Energy Source: Rumen microbes ferment carbohydrates into Volatile Fatty Acids (VFAs)—Acetate, Propionate, and Butyrate—which supply over 70% of the ruminant's energy.
• Milk Fat Synthesis: Fiber fermentation produces Acetic acid, which is the primary precursor for milk fat synthesis in the udder.
• Glucose Synthesis: Starch fermentation produces Propionic acid, which is converted to glucose in the liver (gluconeogenesis).
• Rumen Health: Adequate structural carbohydrates (fiber) stimulate chewing and saliva production (buffering), preventing acidosis.

Essential Amino Acids (EAAs):
These are amino acids that cannot be synthesized by the animal's body at all, or in sufficient quantities to meet requirements, and thus must be supplied through the diet. Examples include Lysine, Methionine, Tryptophan, Threonine, etc.

Difference in Protein Requirements:

1. Poultry (Non-Ruminants):

• Quality Matters: Poultry rely entirely on the amino acid profile of the feed. They require 'High Quality' protein.
• Limiting Amino Acids: The diet must be balanced specifically for limiting amino acids (e.g., Methionine is often the first limiting amino acid in poultry).
• NPN Usage: They cannot utilize Non-Protein Nitrogen (NPN) like urea effectively.

2. Ruminants (Cattle/Sheep):

• Microbial Protein: Rumen microbes can degrade feed protein and NPN to synthesize their own body protein (Microbial Protein), which is later digested by the animal.
• Biological Value: Ruminants are less dependent on the specific amino acid profile of the diet because microbes upgrade low-quality proteins.
• NPN Usage: They can utilize urea and other NPN sources to synthesize protein, provided there is sufficient fermentable energy.
• Bypass Protein: High-yielding animals need 'Bypass Protein' (Undegradable Dietary Protein) that escapes the rumen to be digested directly in the abomasum for higher efficiency.

Minerals are inorganic elements essential for metabolic processes. They are classified based on the quantity required by the body.

1. Macro-minerals (Major minerals):

• Required in large amounts (grams/day or > 100 ppm in diet).
• Examples: Calcium (), Phosphorus (), Magnesium (), Sodium (), Potassium (), Chlorine (), Sulphur ().

2. Micro-minerals (Trace minerals):

• Required in minute amounts (milligrams or micrograms/day or < 100 ppm).
• Examples: Iron (), Copper (), Zinc (), Cobalt (), Iodine (), Manganese (), Selenium ().

Deficiency Symptoms of Calcium () and Phosphorus ():

• Rickets: Occurs in young growing animals. Bones become soft, flexible, and deformed due to failure of calcification.
• Osteomalacia: Occurs in adult animals. Bones become brittle, prone to fractures, and demineralized.
• Milk Fever (Parturient Paresis): Specifically caused by low blood calcium (hypocalcemia) in dairy cows shortly after calving. Symptoms include muscle weakness, recumbency, and unconsciousness.
• Pica: Often associated with Phosphorus deficiency. Animals chew on wood, bones, soil, or rags (depraved appetite).
• Reduced Production: Lower milk yield in cattle and thin-shelled or shell-less eggs in poultry ( deficiency).

Water is often considered the most critical nutrient, as animals can survive longer without food than without water. It constitutes 60-70% of the animal body weight.

Sources: Drinking water, water contained in feed (succulent fodders have 80-90% moisture), and metabolic water (produced during oxidation of nutrients).

Functions:

1. Solvent & Transport: Acts as a universal solvent for nutrients, hormones, and metabolic waste, transporting them via blood and lymph.
2. Thermoregulation: Critical for maintaining body temperature. High specific heat allow it to absorb heat, and evaporation (sweating/panting) dissipates heat.
3. Biochemical Reactions: Essential medium for all enzymatic and hydrolytic reactions (digestion).
4. Body Form: Maintains turgidity of cells and provides shape to the body.
5. Lubrication: Lubricates joints (synovial fluid) and cushions organs (cerebrospinal fluid).
6. Milk/Egg Production: Milk is approx. 87% water; eggs are approx. 65% water. Insufficient water intake drastically reduces production.

Fat-Soluble Vitamins:
These vitamins require fat for absorption and can be stored in the body (liver/fat tissue). They are:

• Vitamin A (Retinol)
• Vitamin D (Cholecalciferol)
• Vitamin E (Tocopherol)
• Vitamin K (Phylloquinone)

Vitamin A (Retinol):
It is not found in plants but is synthesized in the animal body from Carotene (pro-vitamin A) found in green fodders.

Functions:

1. Vision: Essential for the formation of rhodopsin (visual purple) in the retina for night vision.
2. Epithelial Tissue: Maintains the integrity of mucous membranes (respiratory, digestive, reproductive tracts).
3. Growth: Essential for normal bone growth.
4. Reproduction: Necessary for spermatogenesis and maintenance of pregnancy.

Deficiency Symptoms:

1. Night Blindness (Nyctalopia): Inability to see in dim light.
2. Xerophthalmia: Dryness and inflammation of the cornea/conjunctiva.
3. Reproductive Failures: Abortions, birth of weak or blind calves, retained placenta.
4. Infections: Increased susceptibility to respiratory and digestive infections due to keratinization of epithelial lining.

Feed Additives:
These are non-nutritive substances added to feed to improve the efficiency of feed utilization, feed acceptance, or the health and metabolism of the animal.

Difference between Supplements and Additives:

• Feed Supplements: Materials added to the ration to supply specific nutrients that are missing or deficient (e.g., Mineral mixture, Vitamin premix, Urea, Calcium carbonate). They carry nutritional value.
• Feed Additives: Materials added to modify metabolism or health but usually do not supply nutrients themselves (e.g., Antibiotics, Hormones, Flavoring agents).

Examples of Non-Nutrient Additives:

1. Antibiotics (Growth Promoters): Used at sub-therapeutic levels to improve gut health and growth (e.g., Tetracyclines, Bacitracin).
2. Probiotics: Live microbial feed supplements (e.g., Lactobacillus, Saccharomyces) that improve intestinal microbial balance.
3. Prebiotics: Non-digestible food ingredients (e.g., oligosaccharides) that stimulate the growth of beneficial bacteria.
4. Coccidiostats: Used in poultry to prevent coccidiosis (e.g., Amprolium).
5. Antioxidants: Prevent rancidity of fats in stored feed (e.g., Vitamin E, BHT).
6. Enzymes: Exogenous enzymes like Phytase (to release phosphorus) or Xylanase.

Definition:
A Balanced Ration is the feed allowance for an animal for a period of 24 hours that supplies all the essential nutrients (carbohydrates, fats, proteins, minerals, vitamins, and water) in proper proportions and amounts to meet the specific requirements of the animal for maintenance, growth, reproduction, and production (milk/meat/eggs/wool).

Characteristics of a Balanced Ration:

1. Nutritionally Adequate: Must meet the standard requirements (e.g., ICAR or NRC standards) for DCP (Digestible Crude Protein) and TDN (Total Digestible Nutrients).
2. Palatability: The feed must be tasty and acceptable to the animal to ensure proper intake.
3. Digestibility: Ingredients should be easily digestible to minimize waste and maximize absorption.
4. Variety: Should contain a mix of ingredients (legumes, grasses, cakes, grains) to ensure a better balance of amino acids and micronutrients.
5. Bulk/Fill: Must have sufficient roughage to satisfy the appetite and ensure proper rumen function in ruminants.
6. Free from Toxins: Must be free from anti-nutritional factors (like tannins, gossypol) or mold (aflatoxins).
7. Economical: Should utilize locally available ingredients to keep the cost of production low.

Concept:
Total Digestible Nutrients (TDN) is a measure of the energy value of a feed. It represents the sum of all the digestible organic nutrients in the feedstuff. It is expressed as a percentage or in kg. It is roughly comparable to the digestible energy content.

Calculation:
To calculate TDN, we need the digestibility coefficients of the proximate principles. The formula accounts for the fact that fat provides significantly more energy than proteins or carbohydrates.

The formula is:

Where:

• DCP = Digestible Crude Protein
• DCF = Digestible Crude Fiber
• DNFE = Digestible Nitrogen Free Extract
• DEE = Digestible Ether Extract (Fat)

Explanation of Factor 2.25:
Fats (Ether Extract) release approximately 2.25 times as much energy upon oxidation () compared to carbohydrates or proteins (). Therefore, the digestible fat portion is multiplied by 2.25 to equate it to a carbohydrate equivalent.

Note: Water and Ash do not contribute energy and are excluded.

1. Feeding during Dry Period (last 60 days of pregnancy):

• Objective: To allow the cow to regenerate udder tissue, build body reserves for the next lactation, and support the rapidly growing fetus.
• Management:
  • Stop milking (drying off) 60 days before expected calving.
  • Provide good quality leguminous hay and green fodder.
  • Feed restricted concentrates (1-2 kg/day) to maintain body condition but prevent fattening.
  • Steaming Up: In the last 2 weeks before calving, gradually increase concentrate feeding to accustom rumen microbes to high-energy diets and prevent ketosis/milk fever post-calving.

2. Feeding during Early Lactation (0-100 days postpartum):

• Challenge: The cow is in Negative Energy Balance (milk production demand exceeds energy intake capability).
• Objective: Maximize peak milk yield and minimize body weight loss.
• Management:
  • Challenge Feeding: Start with a lower level of concentrate and gradually increase the amount (by 300-500g daily) until the animal reaches peak yield. This challenges the cow to produce her maximum potential.
  • Provide high-energy, high-protein concentrates (Energy density TDN).
  • Ensure unlimited access to clean water.
  • Supplement with mineral mixtures (especially Calcium and Phosphorus) to prevent Milk Fever.
  • Monitor for acidosis; ensure sufficient fiber is still consumed.

Poultry feeding is divided into phases to match the changing nutritional requirements as birds grow.

A. Broiler Feeding Phases (Meat Production):
Broilers grow extremely fast and are marketed at 5-6 weeks.

1. Pre-Starter / Starter (0-2 weeks):
   • Requires high protein for rapid tissue and muscle growth.
   • Crude Protein (CP): 22-23%
   • Metabolizable Energy (ME): ~2800-2900 kcal/kg
2. Finisher (3 weeks - Marketing):
   • Energy is increased for fat deposition; protein is reduced as growth rate plateaus relative to size.
   • CP: 19-20%
   • ME: ~3000-3200 kcal/kg

B. Layer Feeding Phases (Egg Production):
Layers have a longer life cycle.

1. Chick/Starter (0-8 weeks):
   • Focus on organ development.
   • CP: 18-20%
   • ME: ~2600-2700 kcal/kg
2. Grower (9-18 weeks):
   • Focus on skeletal development. Feed is often restricted to prevent obesity and early sexual maturity.
   • CP: 15-16%
   • ME: ~2500-2600 kcal/kg
3. Layer (19 weeks - approx 72 weeks):
   • Focus on egg production. High Calcium requirement for eggshell formation.
   • CP: 16-18%
   • ME: ~2600-2800 kcal/kg
   • Calcium: Increased to 3.5 - 4.0% of the diet.

Protein Supplements:
These are feed ingredients containing more than 20% Crude Protein (CP). They are added to the ration to meet the amino acid/nitrogen requirements of the animal.

Classification:

1. Vegetable/Plant Origin:

• Oil Cakes/Meals: Residues left after oil extraction from seeds.
  • Edible cakes: Groundnut cake (GNC), Soybean meal (SBM), Mustard cake, Cottonseed cake, Sesame cake.
  • Non-edible cakes: Castor cake, Neem cake (processed), Mahua cake (used as manure usually, or detoxified for feed).
• Leguminous Seeds: Pulses, cowpea, soybeans (roasted).

2. Animal Origin:
Generally higher quality protein (better amino acid profile) but strictly regulated to prevent disease transmission.

• Fish Meal: Excellent source of Lysine and Methionine. Used extensively in poultry.
• Meat & Bone Meal: By-product of slaughterhouses.
• Blood Meal: Very high protein () but lower digestibility and palatability.
• Milk By-products: Skim milk powder, whey (used for young calves/piglets).

3. Single Cell Protein (SCP):

• Yeast, algae (Spirulina), and bacteria grown on substrates.

Urea as Feed:
Urea is a Non-Protein Nitrogen (NPN) substance (). It contains approx. 46% Nitrogen. Since , pure urea theoretically has a protein equivalent of CP. Rumen microbes can convert this nitrogen into microbial protein.

Method of Feeding:

• Mixed in concentrate mixture.
• Urea Molasses Mineral Block (UMMB) licks.
• Urea treatment of straw (to improve digestibility of poor quality roughage).

Precautions:

1. Ruminants Only: Never feed to monogastrics (poultry/pigs) or young calves (pre-ruminant stage) as they lack the microbes to utilize it; it is toxic to them.
2. Gradual Introduction: Introduce slowly over 2-3 weeks to allow rumen microbes to adapt.
3. Energy Source: Must be fed with readily fermentable carbohydrates (like molasses or grains) to provide the energy needed for microbes to capture the ammonia.
4. Dosage Limit:
   • Max 1% of the total dry matter intake.
   • Max 3% of the concentrate mixture.
5. Water: Plenty of water must be available.
6. Mixing: Must be mixed thoroughly. Lumps of urea can cause acute toxicity (Ammonia poisoning).

Definition:
Anti-nutritional factors are natural or synthetic compounds found in feed ingredients that interfere with the digestion, absorption, or utilization of nutrients, or are toxic to the animal, thereby reducing performance or health.

Examples:

1. Trypsin Inhibitors:

   • Source: Raw Soybeans.
   • Effect: Inhibits the enzyme Trypsin, interfering with protein digestion. Causes pancreatic hypertrophy.
   • Remedy: Heat treatment (roasting/toasting) destroys them.

2. Gossypol:

   • Source: Cottonseed cake.
   • Effect: A yellow pigment that is toxic to monogastrics (heart failure, liver damage). In males, it impairs spermatogenesis. Also binds to iron causing anemia.
   • Remedy: Use ferrous sulphate to bind gossypol; restricted feeding in non-ruminants.

3. Tannins:

   • Source: Sorghum, Tree leaves (e.g., Oak).
   • Effect: Binds to proteins making them unavailable for digestion (astringent taste reduces palatability).
   • Remedy: Chemical treatment or limited inclusion in diet.

Derivation:
Proteins are complex organic compounds composed of Amino Acids. While they contain Carbon, Hydrogen, Oxygen, and Sulphur, the distinguishing element used for analysis is Nitrogen.

On average, feed proteins contain approximately 16% Nitrogen by weight.

If we let be the amount of Protein and be the amount of Nitrogen:

To find Protein () from Nitrogen ():

Therefore, Crude Protein (CP) = Nitrogen content × 6.25.

Why 6.25?
The factor 6.25 is purely a mathematical constant derived from the assumption that average protein contains 16% nitrogen ().
Note: This varies slightly for specific products (e.g., Milk protein factor is 6.38, Wheat is 5.70), but 6.25 is the standard factor used in Proximate Analysis for general feedstuffs.

1. In Ruminants (Cattle, Buffalo, Sheep, Goat):
Crude fiber is beneficial and essential.

• Energy Source: Rumen microbes ferment cellulose and hemicellulose into Volatile Fatty Acids (VFAs), providing the majority of the animal's energy.
• Rumination: Long fiber particles stimulate the 'scratch factor' in the rumen wall, inducing regurgitation (cud-chewing) and saliva production.
• Buffering: Increased saliva (rich in bicarbonate) buffers the rumen pH, preventing rumen acidosis.
• Milk Fat: Digestion of fiber produces specific VFAs (Acetate) which are necessary precursors for the synthesis of milk fat. Low fiber leads to 'Low Milk Fat Syndrome'.

2. In Poultry (Chickens, Ducks):
Crude fiber is generally considered non-nutritive or a diluent.

• Indigestibility: Poultry lack the rumen and the specific microbes to break down complex fibers effectively. High fiber reduces the energy density of the diet.
• Gut Health: A small amount of fiber is necessary to maintain normal gut motility and consistency of feces.
• Cannibalism Control: Higher fiber diets can sometimes reduce feather pecking by keeping birds satiated (gut fill).
• Limit: Diets usually contain low fiber (max 5-6%) to ensure adequate nutrient absorption.