Intestinal Digestible Protein (IDP)
Definition
Intestinal Digestible Protein is the portion of dietary and microbial protein that can be digested and absorbed in the small intestine of the animal. It consists of two main sources:
- Microbial protein synthesized in the rumen
- Rumen-undegradable feed protein that bypasses rumen fermentation
This measure reflects the actual protein available for metabolism after rumen digestion and is essential for accurate ration formulation and optimizing animal performance.
Rumen Undegradable Protein (RUP)
Rumen Undegradable Protein is the fraction of feed protein that escapes breakdown in the rumen and passes to the small intestine as intact protein. Here, it is digested and absorbed, contributing directly to the animal’s protein supply. This makes Intestinal Digestible Protein one of the most critical parameters in ration formulation.
Link to Milk Production
There is a strong relationship between Intestinal Digestible Protein and milk yield, as well as milk protein content.
- Deficiency in Intestinal Digestible Protein limits milk production.
Excess may stimulate milk production, although this effect is not guaranteed.
Factors Affecting Intestinal Digestible Protein
The content of Intestinal Digestible Protein in feed depends on several factors:
Plant species: Protein-rich plants like grass and lucerne have higher levels compared to corn silage or grain silage.
Fertilisation and turf quality: Well-managed turf with few weeds improves nitrogen utilisation, increasing protein content.
Ensiling method and dry matter: Drier silage often has higher Intestinal Digestible Protein because:
- Protein resistance to rumen degradation is greater.
- More energy remains available for rumen bacteria, boosting microbial protein synthesis.
- Less sugar is converted to acids during preservation, leaving sugars for microbial growth.
