Longread
Downpours, heat and drought: livestock farmers need to adapt to weather extremes
Prolonged droughts, heatwaves and heavy rains: farmers increasingly face weather extremes and need to adapt to a changing climate. Wageningen University & Research develops and shares practical innovations and knowledge to make livestock farming climate-proof.
The climate is changing rapidly, leading to grasslands becoming barren and fields turning dusty. As a result, crops hardly grow, and animals (and crops) suffer from the heat. A few months later, heavy rains may prevent farmers from harvesting their crops.
‘Due to climate change, Dutch livestock farming will increasingly face prolonged droughts, heatwaves, heavy precipitation, warmer and wetter winters and salinisation in coastal areas,’ says researcher Marion de Vries. ‘This will have a significant impact on forage production and farm animal health and welfare. Part of our research is therefore dedicated to climate adaptation. Wageningen Livestock Research shows how farmers can respond to changing climate conditions and exploit opportunities.’
Wageningen Livestock Research shows how farmers can respond to changing climate conditions and exploit opportunities
Heat stress in cows and pigs
One of the major topics is heat stress – an increasing problem in farm animals. Cows, for example, produce heat as they digest their rations. This heat needs to be dissipated through, say, panting and sweating to keep their body temperature constant. ‘At temperatures above 20 degrees Celsius combined with high humidity, cows are less able to release their heat,’ says researcher Ingrid van Dixhoorn. ‘Their behaviour changes; they stand up more and look for cooler places.’
Herman Vermeer adds: ‘Pigs cannot sweat. When they suffer from heat, they lie down on the slatted floor more often and avoid body contact with other pigs. And they eat less. Finishing pigs and lactating sows, in particular, can suffer from heat stress because they produce a lot of heat while growing and producing milk.’
When pigs suffer from heat, they lie down on the slatted floor more often and avoid body contact with other pigs
Heat Stress Stable Map
For all farm animals, heat stress has a negative effect on welfare, fertility and health, thus reducing production. According to Ingrid van Dixhoorn, it is therefore important that farmers recognise the risk signals quickly so they can take the right measures. She worked with colleagues to develop a Heat Stress Stable Map (in Dutch: ‘Hittestress Stalkaart’) with specific cow signals. ‘For measures to prevent heat stress in cows, you could consider lowering the temperature in the barn by cooling the roof or by wetting the cows and combining this with ventilation. In addition, farmers could adjust their management approach by milking their cows in the cooler morning or evening and putting them out to graze at night.’
For cows, you can think of measures such as cooling the roof, milking in the cool morning or evening and grazing at night
Van Dixhoorn also sees opportunities for adjustments to nutrition. ‘If you use more nutrients that can be digested rapidly, cows produce less heat while eating. This can cause rumen acidification, but you can use additives to reduce that risk.’
Cooling
Vermeer is enthusiastic about cooling incoming air with water evaporation to keep pigs cool: high-pressure fogging in the air inlet. This can change the indoor temperature by five to ten degrees.
Cooling incoming air in the pig barn with water evaporation can lower the indoor temperature by 5 to 10 degrees
‘We also looked at a water sprinkler system. Pigs like to stand under it to cool down or lie down on the wet floor,’ says Vermeer. ‘Taking such measures is good for the welfare of the animals, and that’s how you keep production up.’
The only concern with the sprinkler system is hygiene. Pathogens survive better in humid conditions. In addition, urine and manure are more likely to come into contact due to the wet conditions, and there is less chance of collecting them separately. This causes more ammonia emissions. ‘Incidentally, part of the solution can also be sought in breeding,’ says Vermeer, ‘by keeping animals that are genetically better able to cope well with heat.’
Arming against liver fluke snail
Not only do livestock farmers need to arm their animals against heat stress, but climate change also brings other health risks. For instance, the liver fluke snail is becoming more prevalent in peat grasslands.
‘Climate change is causing peat to dry out more often in summer which is increasing land subsidence. To prevent this, the water level is raised, but this plays into the hands of the transmitter of liver fluke: the liver fluke snail,’ says Van Dixhoorn. ‘It thrives in wet grassland. Cows infected with the parasite have lower milk production and grow less well. We are investigating whether giving natural preparations preventively works or whether they are more successful if the cow is infected.’
Mycotoxin formation: preventing fungal growth
Climate change also increases the health risk of mycotoxin formation. These are (toxic) substances produced by fungi present on crops such as grass, maize and cereals or in other feeds. They are responsible for often latent health problems when they enter cows through feed, such as reduced feed intake, lower milk production, reduced fertility and lower resistance.
Farmers can prevent mycotoxin formation by preventing fungal growth. The growth of field fungi can be inhibited by preventing stress situations during crop growth, and fungicides can be used where necessary. The growth of storage fungi can be inhibited by proper ensilage management for forage and by-products and by preventing moisture during the storage of dry feed products.
Drought impacts crops
When the ground is bone-dry for a long time, the yield and quality of forage crops are impacted greatly. The production of grass, maize and other forage crops depends heavily on moisture supply in addition to fertilisation. The water table on sandy soils often drops so far in summer that the roots can no longer use soil moisture as early as spring. They are completely dependent on precipitation. If there is no precipitation, crops can fail.
Drought can create a nitrogen surplus in the soil, which increases the risk of groundwater loading
‘In addition, plants do not make good use of manure because nutrients can only be absorbed with soil moisture. This can create a nitrogen surplus in the soil, which increases the risk of groundwater loading by nitrate leaching,’ says researcher Idse Hoving. ‘What’s more, after a long period of drought, the soil becomes water-repellent, and as a result it takes some time for the plant to access water again when it rains.’
Marion de Vries points out that farmers irrigate substantially more during drought. ‘Our research in the Dutch Achterhoek region shows that the number of farmers irrigating approximately doubled in the dry years from 2018 to 2020. That creates additional challenges for the availability of water in a region, not only for agriculture, but also for drinking water and nature,’ she says. ‘So, it is imperative that we start retaining more water and letting less flow to the sea and that we also use the water we have more efficiently.’
It is imperative that we start retaining more water and use the water we have more efficiently
Improving the quality of sandy soils at De Marke
For dairy farmers in the Dutch Achterhoek region, Wageningen Livestock Research has made an inventory of climate adaptation measures. At Agro-innovation centre De Marke, researchers are testing various adaptation measures in practice to see which ones hold promise.
Project manager Zwier van der Vegte explains that they are working hard at De Marke to improve the soil, which he says is the key to coping with climate change. ‘De Marke is located in a relatively drought-prone region because of sandy soils and little surface water. We are focusing on generating a healthy soil and increasing organic matter by growing grass in rotation with other crops. Grass provides organic matter, is good for soil life and stores carbon. We are also running a trial in which clay is applied to sandy soil. Our research shows that adding clay improves soil structure and allows the soil to retain moisture better.’
Moisture retention is also achieved with deep infiltration drains combined with drip irrigation. The infiltration drains are installed at about eight metres depth and hold water during periods of excess rainfall by allowing it to infiltrate the soil. In times of drought, researchers use the infrastructure to supply water to crops.
Van der Vegte: ‘Some of these crops need less water because they can withstand drought better. The grain sorghum can withstand heat better and needs less moisture.’
Humidification
On the other hand, there is also the issue of too much rainwater (waterlogging). If there is a lot of rain, the soil can become completely saturated, which also results in a loss of production because not enough oxygen reaches the roots. Silage maize is particularly susceptible to waterlogging; plants turn yellow or may even die completely. Hoving: ‘If it is so wet that the ground is squelchy when you walk on it, farmers cannot get onto their land to sow or harvest. If you do go onto the land with heavy machinery, this deteriorates the soil structure.’
Farmers have to make sure they have enough forage in stock so they can bridge a long period of drought or humidity
Incidentally, according to Hoving, compared to arable farmers, dairy farmers are lucky in that grass has the ability to recover fairly quickly. ‘It is becoming increasingly important for farmers to compensate for yield losses in dry or very wet years with the yields in more productive years. This means they have to make sure they have enough forage in stock so they can bridge a long period of drought or humidity. Buffering, in other words.’
Retaining water
Soil and water management play a key role in adequately coping with climate change. Hoving advocates working with water boards and provinces or regional authorities to fine-tune water management. Although farmers draw water from the soil to grow their crops, they too can play an important role in water retention.
‘Together with the ‘Rijn en Ijssel’ water board, we are conducting trials involving artificially flooding grassland near agro-innovation centre De Marke. With the water company ‘Vitens’, we are exploring water infiltration with an underground drip irrigation system. Especially in winter there is excess precipitation reaching farms via streams, canals or rivers. Farmers can retain that water longer if they would infiltrate the water in soils by rolling out a hose to irrigate the field or by opening the infiltration system.’
If farmers do not drain more water than strictly necessary during the winter, this will benefit them during the growing season
The study shows that this can add a lot of extra water to groundwater. This can help restore the natural water system and reduce dependence on irrigation. However, it requires commitment from the farmer. In addition, Hoving points to level-controlled drainage. ‘If farmers do not drain more water than strictly necessary during the winter months, they will benefit from this during the growing season and the impact of drought will be reduced. With connected drains and an adjustable sump, they can retain water and drain it appropriately.’
Salinisation
Climate change and sea level rise will increase salinisation in the Netherlands in the coming decades. This is the increase of salt content in ground and surface water due to penetrating seawater and rising brackish groundwater. Salinisation can have negative consequences for livestock drinking water supply, grassland production and management, and forage cultivation of silage maize. The availability of fresh irrigation water is becoming a problem. This is certainly already an issue in the Dutch province of Zeeland, but it is also increasingly so in other areas.
Longer growing season
Higher temperatures do not have only negative effects, by the way. Warmer winters are expected to allow for a longer growing season, which opens up opportunities for growing winter crops. ‘Dairy farmers can use winter rye to increase their forage production in early spring, compensating for losses due to drought in summer,’ Hoving explains. ‘However, our research shows that it is important that farmers harvest winter rye at boot height to avoid loss of forage value.’
Hoving and his colleagues are also looking at crops that can withstand drought better. They are investigating the effects of herbs in grassland, such as chicory, cocksfoot and clover. ‘These have deeper roots or are more drought-resistant, but if it is dry for too long they eventually perish too.’
Differences between regions
Van Dixhoorn casts another glance into the research future. As far as she is concerned, we should zoom in more on the differences between regions. ‘We have salinisation in coastal areas, drought problems on sandy soils and boggy ground on clay soils. Our aim is to provide farmers with practical solutions that fit their specific farming situation so that they can adapt to climate change in a targeted way.’