Producing Quality Oat Hay

Fibre and digestibility
Digestibility estimates the percentage of forage
that can be readily broken down in the rumen. If
hay is being fed exclusively, digestibility must be
above 58% otherwise animals will lose condition.
Two measurements are used for fibre. Neutral
detergent fibre (NDF) measures how much of
the hay is plant cell wall, the structural part of the
plant that provides ‘bulk’ rather than nutrients in
the diet. A proportion of bulk is required for the
proper functioning of the rumen but too much
will limit intake. The other measure is acid
detergent fibre (ADF) this primarily measures
cellulose, lignin, silica, insoluble crude protein
and ash, which together are the least digestible
parts of the plant. The level of ADF is inversely
proportional to digestibility and it can be used to
calculate energy values.
Water soluble carbohydrates
Water soluble carbohydrates are sugars that can
be readily absorbed into the blood stream to
24 PRODUCING QUALITY OAT HAY
provide energy. High quality oat hay will have a
water soluble carbohydrate content of about
19%. Water soluble carbohydrates, in particular
fructose, influence palatability but may not be
strongly correlated with preference. Current and
future projects may isolate specific carbohydrates
and other compounds that attract animals to eat
one hay in preference to another.
Minerals
Oat hay is generally low in sodium but potassium
and nitrate levels can vary depending on crop
nutrition and availability in the soil. If dry cows
are fed hay with a potassium level in excess of
2%, within three weeks of calving, the potential
risk of milk fever is increased. However, this
will also be influenced by the level of sodium,
chloride and sulphur in the total diet.
Many of the above factors can be manipulated by
crop agronomy and by the way hay is made and
stored. These are discussed in more detail in
Chapters 6, 7 and 8.
Image 3.2 Three examples of premium quality export hay but with increasing stem diameter from left to right.