Impact of grass management on modelled outputs of energy-corrected milk, milk per area, and feed efficiency

Authors: OLLERTZ-MERTENS, BERND - Norwegian University Of Life Sciences; VOLDEN, HARALD - Norwegian University Of Life Sciences; PRESLOKKEN, EGIL - Norwegian University Of Life Sciences; DIGMAN, MATTHEW - University Of Wisconsin; Kalscheur, Kenneth; BUCHNER, BENJAMIN - John Deere & Company

Submitted to: Grass and Forage Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary: Maturity at grass harvest is one of the most important factors affecting forage quality, and consequently, animal performance. Therefore, determining the harvest time of grass is a critical decision on dairy farms. This study evaluated at which maturity stage the harvest would be ideal for three different scenarios using different target variables. These variables were energy-corrected milk yield, milk yield per area, and feed efficiency. Results conclude that there are major variations between years of harvest, number of cuttings per year, and types of grass harvested. However, of all factors evaluated, the maturity stage of the grass harvested had the strongest impact on changes in ECM yield, milk per area, and feed efficiency. This research will be of interest to livestock producers, agronomists, forage scientists, animal scientists, animal nutritionists, and livestock system researchers interested in how determining how forage management factors affect outputs related to improving the performance of dairy cows fed high forage diets.

Technical Abstract: Maturity at grass harvest is one of the most important factors affecting forage quality, and consequently, animal performance. Therefore, determining the harvest time of grass is a critical decision on dairy farms. This study evaluated at which maturity stage the harvest would be ideal for three different scenarios using different target variables. These were energy-corrected milk (ECM) yield, milk yield per area, and feed efficiency. From fifteen different fields on six farms, 429 samples were taken over the course of three years. Samples were analyzed for their constituents and yields were estimated using a 0.25 m² cutting frame. The grass represented permanent grassland, two different ryegrass species, and a mixture of white clover and perennial ryegrass. The ECM yield (kg cow-1 day-1), milk yield per area (kg ha-1), and feed efficiency (kg milk kg-1 feed) were calculated from these inputs. Linear mixed models were computed using farm and field as random effects and the year of harvest, the number of cuttings, the type of grassland and the maturity stage as fixed effects. Results showed that the farmers’ rule of thumb to harvest at heading of the grassland is not viable for all scenarios. There are not only differences between farm setups and goals, but there is also variation between different cuttings, maturity stages, years, and types of grassland as well as interactions between those. The effect of maturity was strongest in first cuttings and not significant in third cuttings. First cuttings showed higher values for all target variables than regrowth. The effect of maturity was different between years of sampling, showing differences above 15% for all three target variables. The ECM yield and feed efficiency were highest in the third sampling year, whereas the milk yield per area was highest in the first sampling year over almost all maturity stages. The type of grassland only showed an interaction with the sampling year for milk per area. The ideal harvest time needs to be adjusted to certain farm conditions, but also to the factors cutting, year, and type. Precision farming technologies can help in decision making on harvest timing.