Topics:
Animal Nutrition, Animal Refresher
Reason for Indeterminable Ash Digestibility
Digestibility of Ash cannot be determined because:
- It does not contribute to energy content of a feed — Correct Answer
- It is not a source of protein
- It is not a source of carbohydrate
- None
Explanation:
Correct Answer: It does not contribute to energy content of a feed
The digestibility of Total Ash cannot be determined because ash (mineral matter) does not contribute to the energy content of a feed. Digestibility in the Weende system is fundamentally linked to energy metabolism, and minerals do not provide caloric energy.
Why Ash Digestibility Cannot Be Determined
- Digestibility = (Nutrient intake − Nutrient in faeces) / Nutrient intake × 100
- For energy-containing nutrients (protein, fat, carbohydrate), this calculation gives meaningful physiological data
- Ash (minerals) is absorbed and excreted independently of digestive processes; some minerals are secreted into the gut lumen regardless of dietary intake
- Ash contributes zero Kcal/g of energy → no energy to "digest"
TDN Formula Confirms This
- TDN% = DCP + DCF + DNFE + (DEE × 2.25)
- Notice: Ash is absent from TDN calculation entirely
Why Other Options Are Wrong
- It is not a source of protein → irrelevant to why digestibility cannot be determined; proteins also don't provide energy directly in one step
- It is not a source of carbohydrate → irrelevant; the reason is specifically about energy contribution
- None → incorrect; the energy-contribution reason is the established explanation
