Farm trial: performance assessment of grazed GS4 mixes

In 2022, AHDB commissioned ADAS to carry out a GS4 mixes assessment on one of our Beef & Lamb Monitor Farms.

The aim of this farm trial was to assess the performance of three different GS4 mixes grazed with sheep, to identify which performed best and help inform future decisions on sown seed mixes.

Glover Farm is in Sedgeford, Norfolk, and farmed by David Cross and his father John. The farm is 360 ha of tenanted land, with around 30 ha sublet to a free-range pig operation. Eighty ha of temporary grassland features heavily within the arable rotation, in addition to barley, wheat, potatoes and sugar beet.

The farm sits predominantly on light alkaline soils over chalk, making it susceptible to drought in the summer months.

The trial was carried out in a 40-ha field. Three different GS4 mixes were sown at two timings (late June and early August) in one field at Glovers Farm, giving six treatments. The three seed mixes are germinal GS4 mix, high legume and herb GS4 mix, and a home GS4 mix.

This farm trial has shown differences in forage production and quality between the three GS4 mixes, which have impacted on livestock performance and stocking rate.

Summary of results

Table 1 shows the average weight gain of the lambs in each group from birth to approximately eight weeks. Weight gain was notably higher on the 'germinal' and 'high legume and herb' treatments, at 372 and 367 g/day respectively, than on the 'home mix' treatment at 315 g/day.

Table 1 also shows the total area grazed by each group and the liveweight gain calculated on a per hectare basis.

At lambing, the 'home mix' treatment was expanded to include 12 ha of 'home mix' sown in a neighbouring field, as grass covers in the 'home mix' area of the treatment field were insufficient for the number of lambs.

The area grazed by the 'home mix' group of lambs was 25.3 ha, compared to 13.9 ha for each of the 'germinal' and 'high legume and herb' treatment groups.

Liveweight gain per hectare for the lambs was 1.50 kg/ha for the 'germinal' group, 1.48 kg/ha for the 'high legume' group, and 0.70 kg/ha for the 'home mix' group.

The lower average liveweight gain per lamb and greater area grazed by the 'home mix' group resulted in a liveweight gain per hectare less than half that of the groups grazing the 'germinal' and 'high legume and herb' mixes.

Table 1. Liveweight gain of the lambs grazing each grass mix

Grass covers were measured for quantity and quality from the three different GS4 mixes three times during the 2022 grazing season. The 'germinal’ and 'high legume & herb' mixes performed better than the 'home' mix. Grass covers were lower on the 'home' mix from November 2021 a few months after sowing, and continued during the 2022 grazing season.

Grass analysis data is shown in Table 2. Forage from the 'home' mix was lower in protein content. This was reflected in lower liveweight gain in lambs grazing the 'home' mix and larger area requirement.

The lower average liveweight gain per lamb and greater area grazed by the 'home mix' group resulted in a liveweight gain per hectare less than half that of the groups grazing the 'germinal’ and 'high legume and herb' mixes.

This highlights the impact that variety mix selection and establishment can have on forage yields, livestock performance and farm productivity.

Table 2. Grass quality analysis: samples taken from the next cell to be grazed

The trial was conducted during the 2022 summer drought, which may have accentuated the differences between the three mixes.

The 'germinal’ and 'high legume and herb' mixes, which had a higher proportion of legumes and herbs performed better during the drought.

Overall, the DLWG achieved during the season were good and above what we think is achieved across the industry each year.