Proximate Principles of Feed

The Weende analysis, developed in 1860 by Henneberg and Stohmann, is a method used to determine the macronutrient composition of animal feed. This analysis divides feed into six major categories based on the chemical properties of the compounds present. Understanding these categories is important for evaluating the nutritional quality of the feed. Here’s a detailed breakdown of the six components:

1. Moisture

• Definition: Moisture refers to the water content in a feed sample.
• Importance: The water content is critical because it affects the weight and volume of the feed. The portion of feedstuff that remains after moisture is removed is known as dry matter (DM).
• Analysis: The moisture content is determined by drying the sample at a specified temperature (usually 105°C) until it reaches a constant weight. The loss in weight represents the moisture content.

Formula:

Moisture % = Weight of fresh sample−Weight of dry sample / Weight of fresh sample × 100

2. Crude Protein (CP)

• Definition: Crude protein represents the total amount of protein in a feedstuff, including both true protein and non-protein nitrogenous compounds such as urea, biuret, and amides.
• Importance: CP is a critical parameter because proteins are essential for growth, tissue repair, and milk production in animals.
• Analysis: The determination of crude protein is based on the nitrogen content of the feed. Since most proteins contain approximately 16% nitrogen, the nitrogen content is multiplied by a factor of 6.25 to estimate the total protein.
• Method: The Kjeldahl method is commonly used for determining nitrogen. The process involves:
  1. Digestion: The sample is treated with sulfuric acid and a catalyst to break down organic material and release nitrogen.
  2. Distillation: The released ammonia is distilled and absorbed into a known volume of standard acid.
  3. Titration: The ammonia solution is titrated with a standard base to determine the nitrogen content, which is then converted to crude protein using the factor of 6.25.

Formula:

Crude Protein (CP)=Nitrogen content × 6.25

3. Crude Fiber (CF)

• Definition: Crude fiber includes less digestible carbohydrates like cellulose, hemicellulose, pectins, and the non-carbohydrate fraction like lignin.
• Importance: Fiber plays an essential role in the digestion of ruminants and in maintaining gut health. It also affects the texture and palatability of feed.
• Analysis: Crude fiber is determined by boiling the sample in a weak acid and alkali solution to remove soluble nutrients and then measuring the residue. The residue contains fibrous material, which is considered crude fiber.

Formula:

Crude Fiber (CF) = Weight after boiling and drying − Weight of ash content

4. Nitrogen-Free Extracts (NFE)

• Definition: NFE represents the portion of the feed that is composed of readily digestible carbohydrates, such as starches and sugars, with smaller amounts of cellulose and hemicellulose.
• Importance: NFE is a measure of the digestible carbohydrates in the feed, which provide energy to the animal.
• Analysis: NFE is calculated by subtracting the sum of the moisture, crude protein, crude fiber, and ether extract from the total dry matter content. It is essentially the digestible carbohydrates.

Formula:

NFE = Dry Matter − (Moisture + Crude Protein + Crude Fiber + Ether Extract)

5. Ether Extract (EE)

• Definition: Ether extract represents the lipid or fat content of the feed. It includes fats, oils, fatty acids, pigments, waxes, and other lipids.
• Importance: Fats are a rich source of energy and provide essential fatty acids, which are important for various bodily functions like maintaining cell membranes and hormone production.
• Analysis: Ether extract is determined by extracting the fat-soluble compounds using a solvent like ether, which dissolves the lipids and separates them from the other components in the feed.

Formula:

Ether Extract (EE) = Weight of extractable fat / Weight of feed sample

6. Total Ash

• Definition: Total ash refers to the inorganic mineral content in the feed, including essential minerals like calcium, phosphorus, magnesium, potassium, and trace elements like iron and zinc.
• Importance: Minerals are vital for bone formation, enzyme activity, and other physiological functions in animals.
• Analysis: Total ash is determined by incinerating the feed sample at a high temperature (usually 600°C) until only the mineral content remains. The remaining residue represents the ash content.

Formula:

Total Ash = Weight of ash after incineration / Weight of feed 

Proximate Analysis Summary

The proximate analysis provides a comprehensive understanding of the nutrient content in feed, aiding in the formulation of balanced rations. Here’s how each component contributes:

Ashing at 600°C for Total Ash and the determination of Crude Fiber involves specialized laboratory techniques, including the use of a muffle furnace to burn the feed sample and isolate the ash, followed by the measurement of fiber content based on weight loss during the extraction process.

Proximate analysis helps in formulating livestock rations, ensuring that animals receive balanced nutrition for their health and productivity.