Grape marc can be used as a valuable source of supplementary nutrition for dairy cows, and recent
research undertaken by the Victorian Department of Primary Industries have linked the feeding of stems,
seeds and skins from wine grapes with potential impacts on methane reduction and milk production.
However it does not come without risks and these risks need to be well understood and managed.
As a by- product of the wine industry, grape marc, made up of skins and seeds presents a risk of containing
residues of agricultural chemicals. This is due to the use of sprays in the vineyards to control pests and
fungal diseases on the grapes. The feeding of contaminated grape marc to dairy cows in turn presents a
risk of the residues being transferred into the milk (and meat) supply.
Raw or unprocessed grape marc is considered to present a particularly high residue risk. Grape marc
supplied through reputable feed companies will be processed using steam distillation which not only
removes excess alcohol and tartaric acid, but is known to reduce (but not remove) the concentration of
chemical resides in the grape marc.
In addition these feed companies regularly test the grape marc for chemical residues to ensure the product
they are selling as stock feed is ‘fit for purpose’. These testing programs underpin the validity of the
vendor declarations supplied to purchasers when buying consignments of grape marc.
As with all sources of purchased stock feed, dairy farmers need to continue to seek assurances regarding
the suitability of feeds before committing them into the ration. Obtaining vendor declarations or buying
from a FeedSafe® accredited stock feed supplier is the way to do this.