To investigate the benefits and trade-offs associated with more frequent cutting, AgriSearch co-funded AFBI studies in 2018 and 2021 comparing three-cut systems with four-cut and three-cut with five-cut systems. The studies examined the impact of harvesting frequency on silage yield, silage quality and dairy cow performance, with the ultimate aim of identifying which system produced the greatest milk output from home-grown forage.
The Studies
In 2018, AFBI compared three-cut and four-cut silage systems using 80 Holstein cows over a 25-week feeding period. A second study in 2021 compared three-cut and five-cut systems using 34 mid-lactation Holstein cows over 21 weeks.
Across both studies, researchers assessed the effect of harvesting frequency on forage yield, silage quality, intake and milk production. The key findings from both studies are summarised in Table 1.
Table 1: Silage yield, quality and cow performance under different cutting frequencies
Outcomes
While caution should be exercised when comparing the two studies directly, as they were conducted in different years using different groups of cows and feeding systems, several clear trends emerged. Increasing harvesting frequency consistently improved silage quality, with higher D-values, metabolisable energy and crude protein concentrations observed in both the four-cut and five-cut systems (Table 1). However, these improvements were accompanied by reductions in total silage dry matter yield per hectare.
When both yield and quality were considered together, total energy production per hectare was broadly similar between the three-cut and four-cut systems (137–143 and 139 GJ ME/ha, respectively). In contrast, the five-cut system reduced total energy production to around 129 GJ ME/ha due to lower forage yields.
The higher quality silages produced within the four-cut and five-cut systems increased voluntary silage intake, allowing cows to consume more energy from forage and convert it into additional milk solids. The four-cut system appeared to offer the best balance between forage quantity and quality, maintaining similar energy production per hectare to the three-cut system while increasing milk solids output by 6.9%. Although the five-cut system delivered the highest silage quality, the additional gains in cow performance were relatively small when compared with the further reductions in forage yield and increased harvesting costs.
These findings align closely with wider research from Ireland and Europe, which consistently shows that increasing harvesting frequency improves forage quality and animal performance but rarely increases annual forage yield.
Using a milk solids value of £4/kg, the additional milk solids produced by the four-cut and five-cut systems translated into a significant increase in milk value compared with the three-cut system (Table 2). The additional milk solids produced within the four-cut system were worth approximately £13,680 for a 100-cow herd over a 180-day winter, while the equivalent value for the five-cut system was approximately £10,080.
It is important to note that these calculations reflect only the additional value of milk solids produced and do not account for the extra costs associated with additional silage cuts, including harvesting, fertiliser and land requirements. These costs will vary considerably between farms and should therefore be assessed on an individual farm basis.
Table 2: Additional milk solids value generated by four-cut and five-cut silage systems compared with a three-cut system
AFBI also completed margin-over-feed cost analyses for both studies. In the four-cut study, margin-over-feed costs increased by 48 pence/cow/day despite higher silage production costs. In contrast, the five-cut system did not improve margin-over-feed costs, as the benefits of improved cow performance were offset by lower forage yields and higher harvesting costs. While these economic analyses were based on historical cost assumptions and should be interpreted with caution, they demonstrate an important principle: maximising silage quality alone does not necessarily maximise profitability.
Practical Implications
Based on the four-cut study, feeding a 100-cow dairy herd for a 180-day winter period required approximately 15 ha of silage ground under a three-cut system compared with 18 ha under a four-cut system, representing an increase of almost 20%.
Before increasing cutting frequency, farmers should carefully evaluate the full cost of an additional cut, including contractor charges, fertiliser requirements, land requirements, labour and machinery costs. While improved silage quality can increase milk solids production, the financial benefit must outweigh the additional cost of producing the forage.
It is also important to recognise that both studies were conducted at AFBI Hillsborough over individual seasons and may not fully represent the performance of multi-cut silage systems on every farm. Factors such as soil type, growing conditions, field layout, distance from the silage pit, labour availability, contractor costs and machinery efficiency can all influence the economics of increasing cutting frequency.
Conclusion
The results from both studies demonstrate that increasing harvesting frequency can improve silage quality, increase forage intake and enhance milk solids production. However, these benefits come at the expense of lower annual forage yields, increased land requirements and higher harvesting costs. While the four-cut system appeared to offer the best balance between forage yield, forage quality, milk solids production and economic return, the optimum number of cuts will vary between farms.
Silage analysis provides valuable insight into forage quality, but it does not tell the whole story. The real measure of success is not the D-value in the pit, but the quantity of milk solids produced from home-grown forage. While milk from forage is often associated with grazing systems, these studies demonstrate that it is equally relevant when evaluating silage systems. Rather than focusing solely on silage analysis, farmers should consider how effectively their forage is converted into milk solids and ultimately profit.