Composition of Saliva | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Rumen Functionality and Digestive Processes in Ruminants

Saliva Composition

• Bicarbonate Phosphate Buffer: Organic phosphate is present as I, and the total carbon dioxide is present as HCO ions.
• Saliva of ruminants retains appreciable concentrations of urea.

Rumen Contents

• Weight: The contents of the rumen in fully fed adult cattle may weigh from 30 to 60 kg, varying with the diet, measurement time, and fermentation rapidity.
• Fermentation Vat: Rumen and reticulum form a fermentation vat where feed undergoes fermentation for about 8 to 24 hours.

Fermentation Process

• Bacteria and Protozoa: Microorganisms in the rumen cause extensive chemical changes, with a population density of up to 10 cells per gram.
• Carbohydrate Fermentation: Despite the complexity of ingested carbohydrates, fermentation results in simple mixtures of volatile fatty acids (VFA) with carbon dioxide.

Volatile Fatty Acids (VFA):

• Acetic Acid: 60-70%
• Butyric Acid: 10-15%
• Propionic Acid: 15-20%
• Influence of Sugars and Starch: Soluble sugars and starches influence the concentrations of propionic and acetic acids.

Gases Produced

Carbon Dioxide: 20-65%

Methane: 30-40%

Protein Digestion

• Ammonia Formation: Ammonia is the principal soluble nitrogenous constituent in rumen fluid, influenced by dietary protein, urea quantity in saliva, and urea diffusion through the rumen wall.

Lipid Hydrolysis

• Triglyceride Hydrolysis: Rumen microorganisms hydrolyze triglycerides to glycerol and fatty acids.
• Fermentation: Glycerol derived from hydrolysis is fermented primarily into propionic acids; phospholipids undergo similar hydrolysis.

B-Vitamin Synthesis

• Cobalt Importance: Cobalt deficiency in the diet leads to Vitamin B synthesis inadequacy within the rumen.
• Bacteria Role: Cobalt, concentrated within bacterial cells, is essential for synthesizing cobalamines, including Vitamin B.
• Consequences: Lack of cobalt causes depressed appetite and poor growth in young ruminants, severity depending on the degree of deficiency.

Ruminant Stomach Functions

Reticulum:

• Contraction: Contracts twice, first to half its size, followed by relaxation, and then a stronger contraction.
• Duration: Takes 7-12 seconds.
• Triphasic Contraction: Extra contraction before ruminating, referred to as triphasic.

Omasum:

• Function: Reduces food particles to finer division.
• Movement: Rotates during reticulum contraction, squeezing excess fluid to the abomasum.
• Capacity: Limited, can't hold food for long.

Abomasum:

• Digestive Juices: Only stomach part that secretes digestive juices.
• Juice Characteristics: Watery with pH around 3, may contain mucus.
• Gastrin Source: Rich source of gastrin.
• Integration: Volume and acidity remain fairly constant, influenced by factors like volume and content.

Integration Evidences

• Reticular contractions reduced with increased abomasal content.
• Flow to omasum occurs after every reticular contraction.
• Abomasal flow increases with an increase in rumen contents.
• Abomasal juice volume and acidity influenced by content and fatty acid levels.
• Acid secretion inhibited at low pH and introduction of acid into the duodenum.

Volatile Fatty Acid (VFA) Absorption

• Absorbed before reaching duodenum.
• Absorption rates increase with decreasing rumen pH.

Microbial Digestion:

• Disadvantages: Energy loss as heat and methane, nitrogen loss as ammonia in rumen.
• Advantages: Utilizes structural carbohydrates, enhances B-vitamin synthesis, urea recycling compensates for low protein.

Basal Metabolism:

• Resting animal's calorie requirement for maintenance.
• Aves and mammals have higher energy requirements as endotherms.

Survival Value:

• Ruminant system beneficial in poor food conditions, though extravagant when food is abundant.