|Interpretation of feed analysis / horses
|An example of an analysis report of a silage for horses (in Finnish)|
Before feeding silage to horses it is important to be sure that the hygienic and nutritional quality fulfils the criterions. The quality of silage can be measured only by feed analysis.
Feed analysis is useful for both the horse owner and the silage producer. Analysis results help in ration formulation so that the nutritional requirements of the animals can be fulfilled. Forage producer in turn can use the analysis when pricing the feed. The information of the analysis also aids in focusing on the possible problems in cultivating, harvesting and ensiling of the grass.
Each feed batch has to be sampled separately and analysed, because the changes in the sward composition and nutritive values are large during progressing growth of the swards, and between different leys.
In Valio Ltd's laboratory the feeds are analysed using NIRS (Near Infrared Reflectance Spetroscopy) technique. Forages are analysed for D-value, neutral detergent fibre and crude protein; and cereal grains for hectolitre weight and crude protein..
It is recommended to mark in the covering letter if the feed will be used for horses. In that case, the result of the concentration of digestible crude protein (g/kg DM) in the feed will be calculated. Digestible crude protein is the official feed protein value for horses in Finland.
The Valio feed analysis report for forages with reference to horses includes the following values :
Silage fermentation quality
Ammonium nitrogen, % of total N
Sum of lactic acid and formic acid, g/kg DM
Volatile fatty acids, g/kg DM
Soluble nitrogen, % of total N
Water soluble carbohydrates (sugars), g/kg DM
Composition (silage, hay):
D-value (digestible organic matter, % in dry matter)
Dry matter, %
Crude protein, %
Neutral detergent fibre, %
Feed unit value, units/kg DM
Feed kg /Feed unit
Digestible crude protein, g/kg DM
Nutritional value of feed
Risk for nutrient deficiencies is increasing with poor nutritional quality of feed, although at the same time some other nutrients may be present in excess. Poor feed quality may result in weight loss, retarded growth, fall in performance and/or problems with digestive system (bloat , diarrhoea). Excess of some nutrients may also be hazardous. For example high number of acute laminitis or rhabdomyolysis may be related to unusually high sugar concentration in forage.
Spoiled, mouldy or soil contaminated forage may cause digestive disorders for a horse such as diarrhoea or bloat. Toxins produced by moulds or poisoning by Clostridium botulinum bacteria are the biggest risks for horses due to poor hygienic quality of feed. When the fermentation quality (check the limit values for concentrations of volatile fatty acids, ammonium nitrogen and soluble nitrogen) of forage is good, the number of mould colonies is normally low. Horses are more susceptible to botulisms than other domestic animals. The risk for botulism is however small when silage dry matter concentration is over 35 % and pH is under 4.5.
Optimal ranges for feed values in forages for horses
|Feed units/kg DM
|ME MJ/kg DM
|Crude protein, %
|Digestible crude protein g/kg ka
|Neutral detergent fibre, %
Optimum values for fermentation quality parameters
||4,0 - 4,5
|Ammonium nitrogen, % in total N
||7 - 10
|Volatile fatty acids, g/kg DM
||20 - 30
|Soluble nitrogen, % in total N %
When the dry matter concentration in silage is higher, the acceptable pH value is also higher. For the 30 % dry matter concentration, the upper limit for pH is 4.3, and for the 45 % dry matter concentration, the pH upper limit is 4,9.
Sugar (water soluble carbohydrates) concentration in forage
High silage sugar concentration has it's benefits, because sugar increases palatability and energy value of the feed to horses, and ensures adequate substrate for lactic acid fermentation to obtain good fermentation quality of silage. However very high sugar concentration may be harmful for horses, as well as big changes in sugar concentration between feed batches.
The sugar concentration of grasses is highly variable. Sugars cumulate when photosynthesis goes on, but sugars can not be used for growth. Plant stresses such as drought, cold weather and low fertilization level increase the sugar concentration in grass. Sugar concentration in grass also varies within day so that it is highets in the evening after the whole day of photosynthesis.
Silages for horse are typically extensively wilted with dry matter concentrations over 50 %. The silage harvest time for horses is normally slightly later than in dairy farms resulting in more mature crop with less leaves in the herbage. During ensiling of dry material, the changes due to fermentation will be small because low water activity limits the anaerobic fermentation. Thus the sugar concentration will not be markedly reduced (converted to lactic acid and VFA) during ensiling. This may lead to silage with high sugar concentration. Compared to traditional hay making sugar losses during silage pre-wilting are somewhat smaller due to shorter wilting time.
High sugar concentration in forages may induce digestive disorders, acute laminitis or rhabdomyolysis and muscular stiffness for horses. This effect is related to fructans which make up a remarkable proportion of sugars in the forage,. The fructans are indigestible in the small intestine of horses. They are however fermented in the caecum of the horses and this is supposed to be the reason for problems caused by fructans. Fructan concentration is correlated with total sugar concentration.
High amounts of other sugars induce muscular disorders or diarrhoea in horses. The limit value for harmful sugar concentration is unknown and there is variation in the appearance of symptoms between horses.
The target D-value of forage depends on the energy requirements of the horses it is used for. For athlete horses, nursing mares and growing foals a D-value around 65-68 % is recommended. For horses in light use, a D-value of 62-65 % is recommended.
The energy value of forages is calculated from D-value: Feed unit value = D-value (%) * 0.16 / 11.7.
Sometimes too high a crude protein concentration in silage may also be harmful for horses. Problems as scab formation in feet or feet swelling have been reported. To avoid these problems horse owners prefer silages that are harvested relatively late and thus the protein concentration is lower.
However, the horse requires protein for growth and maintenance of muscles, bones and other tissues. Protein concentration under 10 % in forage is too low to fulfil the requirements of a horse. To compensate for low protein intake of forage, the supplemental protein feeding (soya bean meal, protein concentrates) must be increased.
Both harvesting time and nitrogen fertilization affect protein concentration in forage. Low fertilization will also limit the growth of grass and thus reduce the yield. Because of the slow growth rate, the sugar concentration will increase. The target protein concentration for training horses is 10- 12 % crude protein in forage, for nursing mares 12 15 % and for horses doing light work 8 10 %.
Low forage protein concentration will severally retard growth and development of foals. The protein requirement for nursing mares is higher than for any other group of horses. Early harvested silage or hay harvested at early growth stage suits best the feeding of foals and nursing mares.