Harvesting Oat Forage at Late Heading Increases Milk Production per Unit of Area

Core Ideas Oat forage harvested in late heading increases yield and milk production per hectare. Oat cultivar Laker reached boot and heading 3‐4 days earlier than ForagePlus. Thermal units (GDD) should be used to report maturity time instead of calendar date.Oat ( Avena sativa L.) is a widely used forage crop in the USA and globally, often integrated in dairy systems where it provides the benefits of diversifying crop rotations. As the forage harvest occurs at a later date, forage yield is expected to increase while nutritive value is expected to decrease. To determine the optimal maturity stage to maximize milk production, a 2‐year experiment with two forage‐oat cultivars (ForagePlus and Laker) and four harvest times (boot stage, 2 days after boot stage, heading, and 5 days after heading) was established in a randomized complete block design with three replications at two locations in Wisconsin, USA. Laker reached the boot stage 4 days earlier and headed 3 days earlier than ForagePlus. Relative forage quality decreased at the same rate with increasing growing degree‐days for both locations, years, and cultivars. Therefore, to maximize milk production per cow through feeding the highest nutritive value forage, harvesting oat at boot stage is recommended. Forage yield increased linearly with increasing growing degree‐days for both locations, years, and cultivars, with steeper slope in Arlington than Madison due to precipitation differences. Model estimates of milk production per hectare in both cultivars increased linearly across the four harvest dates in Arlington. In Madison, milk production per hectare did not change significantly with harvest date. Harvesting oat for forage at late heading can therefore increase milk production per hectare, since the greater forage yield compensates for the reduction in forage nutritive value.