2024’s final grassland challenge
With cows returning indoors and the dust settling on the 2024 grazing year, the unforgiving nature of the year that’s been could have one final grassland management challenge to give – lower grass availability next February.
As part of her presentation titled ‘Future metrics for pasture production and utilisation’, delivered at the Teagasc National Dairy Conference on November 27, Research Officer in Teagasc Moorepark, Dr. Áine Murray reminded dairy farmers of the key grassland management targets required to maintain a profitable and efficient grass-based dairy production system.
Four key targets in relation to the quantities of grass present on farm were stressed: peak cover on October 1 of 1,150kg DM/ha; housing cover on December 1 of 700kg DM/ha; turnout cover in early February of 1,000kg DM/ha; and the cover at the start of the second rotation in early April of 650kg DM/ha. Strategies to achieve these targets at various points throughout the season were discussed at length.
Dr. Áine Murray, Research Officer in Teagasc Moorepark, addressed the Teagasc National Dairy Conference in Limerick on November 27.
However, the most immediate target applicable to dairy farms is closing average farm cover (AFC) of 700kg DM/ha on December 1; a target likely to be missed on many dairy farms nationally, stemming from an inability to reach peak grass cover in October due to reduced levels of grass growth.
Providing that overwinter growth rates remain at normal levels, this could potentially leave farmers with below target opening farm covers next spring, and with that comes the need for careful management.
Delving into the Teagasc repository of grassland research, specifically work undertaken by Dr. Mike Egan and Walsh Scholar, Sarah Walsh, Dr. Murray detailed the most appropriate action to take if such a situation arises.
Discussing a study where opening farm covers of 1,000kg DM/ha and 850kg DM/ha were compared from the period of January 29 to April 2, Dr. Murray illustrated the subsequent differences in pasture production witnessed during the second and following rotations.
Dr. Murray explained: “If you open at an average farm cover of 1,000kg DM/ha versus a lower average farm cover of 850kg DM/ha and no intervention is taken in that first rotation, you will end up finishing your first rotation on a lower farm cover of 400kg DM/ha instead of the ideal 650kg DM/ha.
“Where the average farm cover drops to 400kg DM/ha, after that we see there is a 20% reduction in daily growth rate in April and a 12% reduction in growth rate in May, so there is a big knock-on effect from not correcting your grazing targets in that first rotation."
Along with presenting the potential challenge, Dr. Murray also provided the solution: “One way we can rectify this - if you open at a lower average farm cover of 850kg DM/ha - is by supplementing with silage in that February period.”
Detailing another study undertaken at Teagasc Moorepark which examined the impact of silage supplementation on milk yield over the first 12 weeks of lactation to quantify the impact of low grass supplies in spring, Dr. Murray explained how supplementing with either 3.4kg DM of silage in a high grass scenario or 5.4kg DM of silage in a low grass scenario had no impact on overall milk production over the first six weeks of lactation. However, where silage was retained in the diet at a feeding rate of 3kg DM/day for the following six weeks of lactation, and compared to a scenario where cows were offered only grass, it significantly reduced milk yield.
“When silage was supplemented in February, there was no effect on daily milk yield. However, when supplementation continued from March 17 onwards, there was a big effect on daily milk yield and that had an ongoing effect up until the middle of June. This was reflected in the daily protein yield of the milk as well,” Dr. Murray explained.
Concluding on this element of her presentation, Dr. Murray said: “If faced with lower farm covers next spring, February is the time to rectify it.”