Research Updates

Early lactation dry matter intake

Michael Egan, Sarah Walsh and Michael Kennedy

Grazed grass is the cheapest feed available to support milk production in a pasture-based system in Ireland and is of a superior feeding quality due to its higher digestibility and crude protein, in general, compared to grass silage. Increased spring herbage availability allows for higher daily herbage allowance which has positive effects on early lactation dry matter intake and animal performance. Intake capacity and milk production are the main drivers of dry matter intake in dairy cows. Dry matter intake is lowest at the beginning of lactation but rapidly increases as milk production increases. It was previously reported that a herd’s dry matter intake is about 10 kg DM/cow/day, and dry matter intake increases by approximately 1 kg DM per week for the first 6 weeks of lactation, and 0.5 kg per week until peak intake is reached approximately week 12 of lactation.

A recent study at Teagasc Moorepark examining the intake profile of early lactation dairy cows has shown a significantly greater dry matter intake compared to Lewis et al (2011). Dry matter intake was measured for each week of lactation using the n-alkane technique, and initial results show that dry matter intake at the beginning of lactation is approximately 12.8 to 13.3 kg DM/cow/day, with 20% first lactation animals included in the herd. However the rate at which a cow’s intake profile increases is lower than previously reported; dry matter intake increased by + 0.81 kg DM/cow/week in the first 6 weeks of lactation, and + 0.30 kg DM/cow/week in week 7 to 12 of lactation. Total peak dry matter intake was similar between both studies at week 12 of lactation, with a herd average of approximately 19 kg DM/cow at 20% heifers, however the variation in initial dry matter intake and the increase must be taken into account on farms to ensure animals are fully fed, but also to ensure that feed budgets on PastureBase Ireland are accurate to ensure sufficient feed on farms.

Using slurry to grow grass in 2023

William Burchill, Teagasc/Dairygold Joint Programme

 1. Apply slurry to silage ground to maximise its P and K value

There is a big temptation to use more slurry on the milking platform in 2023 in order to reduce nitrogen costs on this part of the farm. However, we need to remember that the majority of the value of slurry is from its P and K and thus slurry should be targeted to areas of the farm with the highest demand for P and K i.e. silage ground. When spreading slurry on the milking platform target paddocks with low P and K indexes first and the lowest grass covers in spring. Trailing shoe and dribble can be using to apply slurry to cover <1,000 kg DM/ha.  It’s also important to plan out which slurry tank on the farmyard will be applied to the grazing ground v’s the silage ground and at what rate per acre. Knowing what’s in your slurry will help you determine this!   

2. Know what’s in your slurry 

Slurry can be tested for it N, P and K content relatively easily and cheaply by a number of labs across the country. In the winter of 2020/21 up to 128 slurry samples from dairy farms within Teagasc/Dairygold Joint programme discussion groups where tested for its dry matter, nitrogen, phosphorus and potassium contents. The slurry contained 10.7 units N/1,000 gals (applied using LESS in spring time), 5.3 units P/1,000 gal and 27 units K/1,000 gals on average and varied slightly compared to the standard Teagasc values (Table 1). An interesting outcome from the testing was the clear difference in slurry nutrient content depending on which tank the slurry came from (Table 1). When taking slurry samples we recommend you to test a number of different tanks in the farmyard for this reason. Slurry form the covered tanks with higher P and K content should be kept for the silage ground, while more watery slurry from open tanks will be sufficient to meet grazing ground P and K maintenance requirements.

Table 1: Slurry test results from dairy farms across the Dairygold Catchment. 

Based on these results we can also see that using a trailing shoe/dribble bar at a rate of 2,000-2,500 gals/acre will deliver 22 units N/acre or the same as our half bag of urea/acre. High application rates of over 2,500 gallons per acre will supply more N than is required in early spring and can result in a lower efficiency of the slurry N. A better ploy is to spread 2,000 to 2,5000 gal/acre across a larger area of the farm to reduce your fertiliser N bill. Your slurry test results can also be inputted into Pasturebase Ireland to track N, P and K applied across your farm via slurry.

 3. Apply slurry in using dribble bar or trailing shoe at the right time

Moving from spreading with a splash-plate to a dribble bar or trailing shoe will give you an extra 3 units of N/1,000 gals from your slurry. While spreading slurry in spring has the potential to improve slurry N values this is reliant on good grass growing conditions. Given the current value of slurry we should be asking ourselves if we are reluctant to spread chemical N fertiliser at time points during the spring due to poor growing conditions should be spreading slurry either if we want to maximise its nutrient value?

New Cattle Slurry Application Date

Mark Plunkett, Teagasc Johnstown Castle, Co. Wexford

Under the recent review of the nitrates action plan the closed period for the application of cattle slurry and FYM now starts on the 8^thOctober.  Now is a good time to apply any remaining cattle slurry on the farm and have tanks emptied before winter. 

To make best use of valuable nutrients in cattle slurry and reduce farm requirements for expensive bag fertilisers, identify areas of the farm that have an N, P or K requirement. For example such as building grass covers, replenishing or building soil P and K fertility. 

Cattle slurry is an excellent source of N, P & K and nutrient content will depend on slurry dry matter content (see table 1).  Cattle slurry contains significant amounts of P and K therefore prioritise cattle slurry to fields that have a P and K requirement based on soil analysis.  Target slurry to areas of the farm where grass silage has been cut in the last year to replenish soil P and K levels thus replacing expensive P and K fertilisers.

Cattle slurry contains available nitrogen (N) and is a valuable source of N to build grass covers currently.  To maximise grass growth aim to apply as soon as possible as the response to applied N decreases at this time of year due to reduced day length.  Therefore earlier application will increase grass growth, aim to apply 1500 - 2000 gallon per acre, which will supply ~ 15 to 20kg N /ha (12 to 16 units N/ac).  This is sufficient N to grow ~ 0.6 to 0.75t DM/ha.  Use LESS technology to maximise the recovery and utilisation of N by the grass plant.

Recent research shows that autumn application of potassium (K) compared to spring application of K increases fertiliser nitrogen use efficiency (NUE). (See figure 1 below from Thomas McCarthy, Johnstown Castle Research Centre)

Autumn Fertiliser Advice- 6th September 2022

The rain over the weekend in most of the drought affected areas of the country has farmers asking about the best approach to the application of nitrogen fertiliser on grassland.  It is essential that a balanced approach be taken, which will help to meet forage requirements and avoid losses of nitrogen to water. There are a number of factors to be considered including:

• Lack of grass growth during August and the requirement to feed animals during the drought have reduced stocks of winter feed on many farms.
• On lower stocked farms, there may be sufficient nitrogen (N) in the soil to meet requirements, provided rotation length is extended.
• Where there is the demand, it is recommended that 15 – 25 kg of N per hectare (ha) (12 - 20 units per acre) be applied immediately on grazing land.
• Grazing rotation length should be extended to greater than 30 days. Continue supplementary feeding where grass covers are low to build up covers on the farm.
• Preference should be given to applying slurry/soiled water, where available, which should be applied immediately to replace artificial N. The use of low emissions slurry spreading (LESS) technology will facilitate earlier grazing and get the maximum value from the nitrogen in the slurry/soiled water.
• It is important to remember that the closed period for slurry application begins on 8 October this year (1 week earlier than 2021).
• Given that we are now in September, growth rates are falling due to reducing day length and care is needed to match nitrogen application with potential uptake of nitrogen by the grass crop. 

The closing date for application of artificial fertiliser is Wednesday 14^th September. 

If you are concerned about winter feed stocks on your farm, contact your Teagasc adviser to prepare a fodder budget for the winter ahead.

Maintenance P and K requirements for Grass and Silage 

William Burchill

Figure 1. Maintenance P and K requirements for a grass cover of 1,500 kg DM/ha depending on weather it is grazed or cut for bales.

The maintenance P and K requirements of a paddock in any given year will depend on the yield of the paddock and weather the paddock was primarily grazed or if there were, surplus bales cut on the paddock. Figure 1 highlights the amount of P and K removed from a cover of 1,500 grass DM/ha. Up to 10 times more K can be removed from a paddock when it is cut for bales v’s grazing. When grazed cows will recycle 90% of the K in the grass back on to the paddock in dung and urine. If baled 100% of the K in the grass is removed from the field. A typical bale of silage contains 10 units of K and 1.7 units of P.

For example if a paddock was grazed 6 times so far this year and will be grazed another three times before the end of the year the maintenance requirements can be worked out roughly as follows:

9 grazing x 3 units K/grazing = 27 units K/acre

9 grazing x 1.7 units P/grazing = 15.3 units P/acre

 This changes significantly, where surplus bales are taken. For example if the same paddock was grazed 8 times in the year and cut for surplus bales once at a yield of 4 bales/acre the maintenance requirements for K are as follows:

8 grazing x 3 units K/grazing = 24 units K/acre

4 bales/acre x 10 units K/bale = 40 units K/acre

Total = 64 units K/acre

Now is the time to look at PastureBase and assess how many grazings and silage cuts have been taken off your paddocks. Calculate how much P and K has been applied this year in the form of slurry and fertiliser and apply P and K to paddocks that require it for maintenance

Fertiliser for First Cut Silage in 2022

Michael O'Donovan, Teagasc Moorepark, Fermoy, Co. Cork

With fertiliser costs much greater this year, farmers will be trying to make savings on this input.  We have already seen excellent usage of slurry this spring on grazing ground and this should continue on silage ground in the next weeks. The recommended application for silage ground is approx. 2500 gal/ac which should supply 25 kg N/ha or 20 units/ac.

It is understandable that farmers will seek to make savings on fertilizer N this year, however there are two key points to consider.

1) Marginal response to additional N
2) Cost of replacing any reduction in silage produced from the marginal N applied

All feed costs have increased this year, so it is important that farmers retain the level of self-sufficiency they have had in previous years as much as possible. Grass silage, harvested at the correct stage, is a highly competitive feed. Do a fodder budget (available on PastureBase Ireland) to calculate silage requirement for next winter.

For first cut silage the guidance is to have at least 25 kg N/ha supplied from organic sources (slurry) and the remainder 60-75 kg N/ha (48 – 60 units/ac) supplied from chemical N, a total N application of  no more than 100 kg N/ha (including 12-15 units of sulphur) for a crop growing from early April to late May (60 days). Where no organice sources available, apply 100 Kg N/ha using chemical fertiliser. 

Figure 1 illustrates a typical response curve to fertilizer N for first cut silage. At a 0 kg N application approx. 3.7 tonne DM will be grown. There is a high growth response to N applied but the marginal rate of response declines as the application rate approaches 140 kg N/ha. In other words, the amount of extra silage grown by the final 20 kg N applied is substantially less that the first 20 kg N applied. At higher N application rates, or on lower grade silage ground (i.e. poor soil fertility, less productive grass types), the economic response to the extra fertilizer N may not be justified, especially this year.   

Figure 1. Silage DM yield response to increasing fertilizer N (fertiliser and slurry) for first cut.

There is a false assumption that ‘one big cut’ will reduce costs and secure enough feed for the winter. It is clear from recent fodder deficits that farms which fail to cut first cut by the June bank holiday (June 6^th in 2022) at the very latest are much more likely to run short of silage in a difficult year.  A delayed heavy first cut actually reduces annual DM yield and quality, and can create problems salvaging second cut crops later in the year (remember, 70% of grass growth has taken place by August). Farms that routinely take earlier first cuts have higher annual silage yields and quality. Drystock farms should close up enough ground and try secure most of thier winter fodder requirement through first cut silage (this will be the lowest cost silage made).

PastureBase Review 2021 - Beef & Sheep

Michael O’Leary from PastureBase Ireland reviews the 2021 grass production data on beef & sheep farms where the data suggest an increase in grazing events per paddock in 2021.

Beef farms in 2021 grew similar grass dry matter (DM) production when compared with 2020. All farms in this data completed 20 covers or more in the given year. Sheep farms although having low number of farms in the data set (19) outperformed their beef farm counterparts (93) by approximately 1 tonne of DM/ha. Sheep farms grew on average 11.05 tonnes DM/ha in 2021 which is a reduction of 0.1 tonnes DM/ha, while beef farms grew on average 10.1 tonnes DM/ha which was in line with 2020 values. Both enterprises witnessed a decrease of 0.5 – 0.6 tonnes DM/ha less silage conserved when compared with 2020. This lead to an increase in the number of grazings per paddock in 2021 when compared with 2020, which is a very positive move. In addition to this the pre-grazing yield on beef farms decreased indicating that farmers offered a higher quality sward to their livestock. We encourage more beef and sheep farms to start using PastureBase Ireland. For more information email support@pbi.ie or 046-9200965.

Using Slurry To Grow Grass In 2022

William Burchill PhD, Teagasc/Dairygold Joint Programme 

The value of slurry has essentially doubled in the last twelve months due to the increase in fertiliser costs and now stands at around €40 per 1,000 gals of cattle slurry. With this in mind here are 3 steps to maximise the use of slurry on your farm in 2022;

1. Apply slurry to silage ground to maximise its P and K value

We need to remember that the majority of the value of slurry is from its P and K and thus slurry should be targeted to areas of the farm with the highest demand for P and K i.e. silage ground. When spreading slurry on the milking platform target paddocks with low P and K indexes first and the lowest grass covers in spring.

2. Apply slurry in spring using dribble bar or trailing shoe to maximise its N value

Moving from spreading in the summer time with a splash-plate to a spring time with a dribble bar or trailing shoe will give you an extra 6 units of N/1,000 gals from your slurry. While spreading slurry in spring has the potential to improve slurry N values this is reliant on good grass growing conditions, so ensure conditions are right for spreading i.e. trafficability, soil temp, weather forecast etc. Trailing shoe and dribble can be used to apply slurry to grass covers up to 1,000 kg DM/ha. 

3. Know what’s in your slurry and adjust your application rate to suit

Slurry can be tested for it N, P and K content relatively easily and cheaply by a number of labs across the country. In the winter of 2020/21 up to 128 slurry samples from dairy farms within Teagasc/Dairygold Joint programme discussion groups where tested for its DM%, N, P, and K contents. On average the slurry contained 10.7 units N/1,000 gals (applied using LESS in spring time), 5.3 units P/1,000 gal and 27 units K/1,000 gals and varied compared to the standard Teagasc values (Table 1). Based on these results, slurry applied at 2,000 gal/acre using a trailing shoe/dribble bar in spring will supply 21 units N/acre.

The standard N recommendation in spring is to apply 23 units N/acre in early February if ground and growth conditions are suitable. Based on this recommendation and the results of the slurry tests we can see that using a trailing shoe/dribble bar at a rate of 2,000-2,500 gals/acre will be the most efficient method to meet these N requirements using slurry. Heavier applications of slurry using a trailing shoe/dribble bar will supply more N than is required at this time of the year. Instead the slurry should be spread out over a larger area and used to replace the standard ½ bag urea or 23 units N/acre to reduce your fertiliser N cost this spring.

Table 1: Slurry test results from dairy farms across the Dairygold Catchment spread using LESS (low emission slurry spreading) in spring.

PastureBase Review 2021 Dairy

Michael O’Leary from PastureBase Ireland reviews the 2021 grass production data on dairy farms where the national figures indicates a reduction of 400kg DM/ha across dairy farms measuring 30 covers or more compared to 2020.

 Grass measuring and budgeting is the cornerstone of all ruminant production systems in Ireland. PastureBase Ireland has seen a steady increase in the number of farmers using in application in recent years with 2,623 farms now recording >10 covers in 2021 an increase of 11%. The following analysis describes the findings from dairy farms who have recorded 30 covers or more in 2020 (810 farms) and 2021 (1,010 farms).

The national picture shows that the average dairy farm on PBI grew 400kg DM/ha less grass in 2021 when compared with 2020 (13,011 vs 13,407kg DM/ha).

However when a matched sample of 650 dairy farms, was analysed a reduction of 300kg DM/ha was seen with the south east most affected with a reduction of 434kg DM/ha while farms in the north west were least affected, with a slight reduction of  just 8kg DM/ha.

As a result of less grass growth in 2021, 247kg DM/ha less silage was conserved for this matched group of dairy farms. Another key finding saw the number of grazings increased slightly (0.3) from 7.4 in 2020 to 7.7 in 2021. This lead to a decrease in pre grazing yield from 1,576kg DM/ha in 2020 to 1,527kg DM/ha in 2021. Both the increase in the number of grazings and reduction in pre-grazing yield shows that farmers are making proactive informed decisions.