Topics:
Animal Nutrition, Animal Refresher
Cause of Brown Color in Hay
The brown colour of Hay is mainly due to:
- Maillard type reaction — Correct Answer
- Butyrate reaction
- Lactic acid production
- None
Explanation:
Correct Answer: Maillard-type reaction
The brown colour of hay (especially "mow-burnt hay" or "brown hay") is due to the Maillard-type reaction — a non-enzymatic browning reaction between reducing sugars and free amino groups (especially the ε-amino group of lysine). This occurs when hay is baled at high moisture content, generating heat through microbial fermentation.
Maillard Reaction in Feed — Key Facts
| Parameter | Detail |
|---|---|
| Reaction type | Non-enzymatic browning (sugar + amino acids) |
| Most susceptible amino acid | Lysine (ε-amino group is reactive) |
| Result | Brown colour, reduced protein digestibility |
| When it occurs | High-moisture hay (>25% moisture at baling) |
| Product formed | Brown hay / Mow-burnt hay |
Impact on Nutritional Value
- Maillard-reacted lysine is biologically unavailable — it cannot be absorbed even though it is detected by Kjeldahl N analysis.
- This leads to overestimation of CP by proximate analysis in heat-damaged hay.
- Vitamin A content also lost up to 80% during sun-drying of hay.
- Vitamin D content is high in hay due to UV-mediated ergosterol conversion.
Why Other Options Are Wrong
- Butyrate reaction → butyric acid fermentation produces bad-smelling silage; not responsible for hay browning.
- Lactic acid production → a desirable silage fermentation process; not involved in hay browning.
- None → Maillard-type reaction is the established cause of hay browning.
