Making better grazing management decisions in 2022 – the PastureBase Ireland story

Enhanced grazing management has the potential to yield further improvements in milk production efficiency and nutrient use efficiency. The level of grassland measurement within PastureBase Ireland has grown substantially in recent years. Michael O’Donovan and Micheal O’Leary, Teagasc, examine this.

Summary

• There has been a 7% increase in the number of farms measuring grass in 2021 (3,813 versus 3,549)
• The total number of farm covers recorded by farms has increased by 12% in 2021
• The top 25% of highest performing farms grew 14.5 t DM/ha with 9.1 grazing/silage events, compared to the bottom 25% which grew 9.0 t DM/ha with 5.6 grazing/silage events
• Mid-season pre-grazing yield is too high on many farms averaging >1600 kg DM/ha during May, June and July periods.

Introduction

Enhanced grazing management has the potential to yield further improvements in milk production efficiency and nutrient use efficiency. To maintain this comparative advantage, considerable research and development has focussed on increasing grass production and the direct consumption of grass under grazing. While maintaining grass production and utilisation will continue to be a challenge, other challenges are emerging in terms of environmental impacts (greenhouse gas emissions and water quality). 

The level of grassland measurement within PastureBase Ireland (PBI) has grown substantially in recent years, over the period 2017-2020, the number of grassland farmers using PastureBase Ireland has increased from 2,696 to 3,664, while the number of grass cover measurements completed per farmer has increased from 14 to 19, and this increased further to 20 walks per farmer in 2021. In 2021, there was an increase of 7% in the number of farms measuring grass (3,813 vs. 3,549) and 12% more grass covers were completed.

While this level of engagement is extremely positive, it has not been possible until recently to begin to analyse some of the results of the data coming into the database. In total, 983 farmers completed > 30 measurements in 2020, which was the dataset used to compile this paper.  Nationally, the representation was extremely good with many counties having large numbers of farmers measuring. The objective of this paper is to investigate the major differences between farms who have a large number of measurements completed in PBI.

Grass DM production and grazing management

In 2020, the mean grass DM production for the 983 farms was 12.5 t DM/ha with 7.4 grazings/silage events. The breakdown on a quartile basis shows that the top 25% of the highest performing farms grew 14.5 t DM/ha with 9.1 grazing/silage events, compared to the bottom 25%, who grew  9.0 t DM/ha with 5.6 grazing/silage events, a difference of 5.5 t DM/ha and 3.5 grazing/silage events. The difference in grazing days between these quartiles was 17 days (280 vs. 263), however the top 25% of farms are allocating substantially more grass, based on their growth figures (Figure 1).

Figure 1: The number of grazings and silage events linked to total DM production on farms measuring > 30 occasions in 2020

Grass DM production in mid-season and autumn for the top 25% of farmers was higher by 1,798 kg DM/ha in mid-summer and 1,350 kg DM/ha in autumn compared to the bottom 25% (Figure 2).

Figure 2: The seasonal DM production differences between quartiles

Mid-season pre grazing yield

The primary objective during the main grazing season is to maintain high animal performance from an all-grass diet, while at the same time maintaining pasture quality. In general, from late April onwards, grass supply exceeds demand, and pre-grazing pasture mass should be maintained at 1,300 to 1,600 kg DM/ha, with a grazing residual of 50 kg DM/ha (4 cm post-grazing height). Excellent pasture quality is required to maximise the potential animal performance from pasture in summer. From mid-April to mid-August, farm cover should be maintained between 160-180 kg DM/cow with a rotation length of 18-21 days, with the aim of achieving 5-6 grazings/silage cut rotations and utilising 7,000-8,000 kg DM/ha, in that period. Improving pasture quality offers the potential to achieve further increases in animal performance from pasture.

The management of grassland mid-season continues to be a problematic area for a lot of farmers, which is apparent from the commercial farm data available from PBI.  Over 50% farmers maintained a pre grazing yield of >1,650kg DM/ha in the mid-season, which is excessive.

The key aspect of all the grass DM production data originating from PBI is the very small regional difference in DM production observed. Figure 3 shows the DM production difference between counties in 2020. There was little difference in DM production between counties and very many of the Midland and North Western counties are preforming very well. While some of the farm numbers are small in these counties, it is not surprising that the differences are small as the farmers who are measuring grass would tend to be the better grassland farmers in those respective areas.

Figure 3: The county difference in DM production in 2020

Implications

There continues to be a reasonable level of uptake of grassland measurement and PBI usage. It is important that the level of grass measurement and grazing management continues to improve. Within this dataset, which is somewhat biased as all the farms have >30 measurements completed, there is very little difference in DM production between the different regions. Grazing management imposed can overcome many of the perceived location effects. On the highest producing farms, irrespective of season, these farms continued to achieve the highest DM production. While there is very little difference between the number of covers completed between the different quartiles of farms, it is the decisions made by the farmers which drives the differences between farms.

This article was produced as part of the two-day Virtual Dairy Conference 2021 which took place on 23 and 24 November.

The complete Dairy Conference Proceedings can be viewed here and the individual articles will be published on Teagasc Daily throughout the week.