Impact of feeding level on digestibility of a haylage-only diet in Icelandic horses.
Authors: Ragnarsson S, Lindberg J E
Journal: Journal of animal physiology and animal nutrition
Summary
# Editorial Summary Ragnarsson & Lindberg (2010) investigated how feeding quantity influences the nutritional extraction from haylage-only diets in mature Icelandic horses, using a crossover design with eight geldings offered either maintenance-level (10.7 g dry matter/kg bodyweight) or 1.5× maintenance intake (18.1 g DM/kg BW) across two 23-day periods. Six-day faecal collections at the end of each period revealed substantially higher apparent digestibility coefficients for dry matter, organic matter, fibre fractions and energy at the lower feeding level, with neutral detergent fibre showing the most pronounced difference between treatments, whilst crude protein digestibility remained unaffected by intake rate. The digestible energy content of the haylage declined from 11.3 MJ/kg DM at maintenance feeding to 10.6 MJ/kg DM when horses received 50% additional forage, representing a clinically meaningful reduction of approximately 6% in available energy. For practitioners working with haylage-fed horses—particularly those relying heavily on forage in competition or maintenance situations—these findings suggest that feeding level exerts significant influence over actual energy extraction, implying that higher intakes may necessitate superior forage quality to maintain target energy availability, and that calculated feeding values cannot be applied uniformly across different intake scenarios.
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Practical Takeaways
- •Feeding haylage at maintenance levels rather than 1.5× maintenance improves digestibility and energy extraction in Icelandic horses, potentially reducing feed costs and waste
- •When calculating energy requirements for haylage-fed horses, account for the feeding level used—the same haylage will provide ~6% more digestible energy at maintenance feeding than at elevated intake levels
- •Haylage quality assessment for energy content should consider the horse's expected feeding level, as digestibility is not constant across different intake rates
Key Findings
- •Coefficient of total tract apparent digestibility (CTTAD) for dry matter, organic matter, NDF, ADF, and energy was significantly higher at low feeding level (10.7 g DM/kg BW) compared to high feeding level (18.1 g DM/kg BW)
- •Feeding level did not affect CTTAD of crude protein
- •Digestible energy content of haylage decreased from 11.3 MJ/kg DM at low feeding level to 10.6 MJ/kg DM at high feeding level
- •NDF showed the largest difference in CTTAD between the two feeding levels