Prolonged dry weather conditions – Considerations for dairy farmers

Date published: 14 June 2023


Prolonged dry and hot weather conditions can have a significant impact on grass growth and supply on some farms.


Some Grass Check sites in the southeast have recorded only 3mm rainfall in the past 4 weeks and, with the potential for further dry weather, grass supply will become limited as soil moisture deficits continue to impact on growth.                 

Grass Check highlights that growth is well below the previous 10-year average. Growth rates on farm have dropped significantly with average farm cover now below target on many farms. This has restricted grass supply on farm already and it’s now likely to have serious implications on growth for the remainder of June.

Given the risk of sustained dry weather, it is important that prompt actions are taken to manage the situation in terms of both current daily herd intake, and budgeted forage requirements for the herd this winter.

Grazing management tips

The main priority now is to reduce daily grass demand to below daily growth rate. This will help to hold grass cover on the farm, protecting current growth and speeding up recovery when rain arrives.

Rotation length should be maintained at 25-30 days, this means grazing no more than 4% of the grazing block on your farm daily. Assess the grass available on this area and supplement with forage and concentrate to balance herd demand.

If there is a larger deficit between growth and demand it will be necessary to temporarily reduce demand further by reducing stocking rate on the grazing block and feeding extra silage.

Maintain normal fertilizer N applications after grazing if possible.  However, if drought conditions persist to greater than 60mm soil moisture deficit it is advised to delay N until rain is forecast, the East of the province moved into this situation last week.

Hints and tips on feeding out forage supplements in dry weather

Currently on many farms where average farm cover has significantly dropped the only option is to feed additional forage and supplement the herd to maintain production. Each farm will have its own preference (based on facilities/machinery/labour) but the main aim remains to reduce total daily grass intake to the level of daily growth or below. Some of the best options for feeding include:

  1. 100% silage and meal in a shed or a convenient paddock, this may be a paddock marked for reseeding later in the year. A small area of fresh grass can be allocated to the herd daily. Some farms have used a temporary wire feeding rail to good effect. This approach simplifies grazing management of the main group. However, there is a risk of injury due to slippery concrete floors if feeding in a shed and adequate space is needed.
  2. Offer silage to all cows in the grazing paddock, placing silage along perimeter fencing if possible. This works best where feed can be allocated with a diet feeder. Silage allocation should be calculated to balance available grass on the paddock daily. Forage should be spread along a long linear distance (1m per cow) to reduce bullying.
  3. Feeding silage swards or zero grazed grass from outlaying blocks can fill a grass supply deficit. However, this should be based on pre grazing cover. If silage swards have surpassed ideal pre-grazing grass cover and are nearing cutting stage then it is preferable to leave for silage cutting at this stage;
  4. High fibre straights can be offered such as palm kernel, soya hulls, beet pulp or other forage reducing straights. These are best fed in mobile troughs or as part of the mixed ration.
  5. With the hot and dry conditions ensure full access to clean water, if feeding in a paddock additional water access maybe required.

Whichever actions are chosen, it is vital to act now to ensure that any remaining grass supply is rationed out as early as possible. Also plan to supplement with forage and concentrate until grass growth exceeds demand.

Additional concentrate can be an effective and easy solution

It is important to ensure that dry matter intake is maintained during prolonged periods of dry weather, feeding additional levels of concentrate will undoubtedly adjust the forage to concentrate ratio of the diet. If managed correctly this is more effective than the alternative of depressed dry matter intake diets which will impact production in the short term, and also have negative knock-on implications for later in lactation.

Parlour-fed concentrate will form a major part of daily feed allowance in drought conditions. Some guidelines for this include:

  • M+ parlour feeding for grazed herds is likely to differ from normal settings at this time of year. If you usually assume grass at this time of year produces M+ 14 litres, remember that this only holds true for ad lib quantities of high-quality grass. If grass is poor quality or simply is not growing, then major M+ adjustments may be necessary.
  • Feed additional parlour concentrate up to a maximum of 50% of the diet dry matter. This is a relatively safe level provided adequate water is provided.
  • Crude protein should be decided based on overall composition of the diet. In normal circumstances a 14-16% high energy ration would be adequate at grass. However, during a drought it is likely that lower protein ingredients will form a significant part of the diet with a small percentage of the diet actually fresh grass. Also, where grass is drought stressed and lacking N uptake, it is possible that sward protein content could be lower than normal. Therefore, it is recommended that a higher protein ration be used if grass intake is restricted for example 16-18% protein.  Grass samples taken over these past few weeks have shown lower than normal protein levels so care needs to be taken to not underfeed protein.
  • Cows in the first half of lactation should always be given preferential treatment and fed the highest quality feed that is available on the farm.
  • Where a dry matter intake deficit exists, this should be filled with the best value for money feeds on a dry matter basis. This could include a range of options from silage, concentrate, alternative fibre sources, standing wholecrop or standing maize (later in the season).

Other key management considerations for your farm

  1. Housing.

Where cows are grazing by day and being housed at night, consider grazing at night and housing during the day.

If housed cows are tightly stocked in warm weather, this will further add to stress on animals. Do not overload cubicle houses in warm conditions.

Feeding silage on a “little and often” basis for housed cows should help to reduce feed spoilage.

Cows should be observed for signs of heat stress during warm weather. Cows become lethargic and inactive and will often stand with heads bowed and panting. Respiration rates will also increase. To alleviate heat stress, cows should be given access to shade and air flow increased for example, with fans.  Heat stress can not only adversely impact milk yield but a number of farms have already reported a drop in fertility performance which may too be a direct result of heat stress. 

  1. Youngstock.

Do not neglect youngstock - total dry matter intake requirements are small relative to the milking herd but nonetheless adequate feed must be offered daily.  Experience from other drought periods highlighted a downturn in heifer DLWG (daily liveweight gain), even when stock seemed content. So additional purchased concentrates may be necessary to maintain growth rates.  This is especially important for herds aiming to calve in heifers at 2 years of age.

  1. Persistent dry period

Late lactation cows in poor condition should be dried off early to ease pressure on the best quality feed. Consider offloading problem cows that are already in line for culling.

If silage must be fed for a few weeks in summer, complete an early fodder budget. This will allow plenty of time to take action if there is a risk of feed shortages later in the year.

Notes to editors: 

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