Cooling cows under Europe temperate climate conditions

    

The principal factors affecting world dairy sectors in summer are climate change (global warming) and the Increase cow’s productivity. The high yielding cow generates more than 2000 W of heat (like 25 persons), which is much above her capability to dissipate, in a typical summer day. The cow in Germany will start suffering from heat stress (HS), being above Temperature Humidity Index (THI) of 65, (earlier than cows in warm climates, due to the fact they are less adapted to heat). It will happen at 23 C when relative humidity (RH) is 20%, 20 C when RH is 50% and 18 C when RH is 80%. The negative impact of summer on cow’s performance is usually related to the number of hours per day and per year, in which cows are subjected to conditions of THI threshold (as said, THI 65 in Germany). Cows under heat stress stand and crowd for longer time, and seek for wetted and shaded areas. Heat stressed cows reduce eating and increase drinking water, while reducing rumination and resting time. Under such conditions, respiration frequency (panting) increase above > 60 breaths per minute, while cow’s body temperature goes above 39.0 C.

Under prolonged heat stress, “peak lactation”, annual milk production as well as milk fat and protein content in milk decrease, while Somatic Cell Count (SCC), increase. Under these conditions, there is a drop in conception and heat detection rate. Feed efficiency (converting feed to milk) is reduced, as cows need to invest part of the energy consumed for activation of body mechanisms for heat dissipation. Cow’s immune system weakened under heat stress conditions, causing the increase in health problems, especially udder and reproductive system diseases.

There is little information so far, regarding the performance losses caused by summer heat stress in West Europe and temperate climates in general, and in Germany in particular. Recent data from different parts of Germany (monthly averages of milk production per cow in the period 2017 – 2023) shows a clear drop of approximately 2 kg/d in milk production in summer and autumn months, as compared to winter. No difference between seasons in average days in milk (DIM) was reported, indicating that the observed drop in production is mainly related to the direct effect of summer heat load on the cows. Some other studies show a significant drop in conception rate of cows inseminated before, during and after heat waves occurring in summer, as compared to those obtained in the winter. Variability in the negative impact on milk production and fertility is due to the big variation between years (number and duration of heat waves per year). Based on studies carried out by german researchers, it is expected that at the end of the century, the number of annual stress events will increase by up to 2000 hours, and the duration of these events will increases by up to 22h, as compared to the situation in the beginning of actual century. It is anticipated that up to one tenth of all year hours and one third of all year days will be classified in Germany as critical heat stress conditions. Due to heat stress, milk yield will decrease by about 3.5% relative to the present European milk yield, and farmers may expect financial losses in the summer season of about 6.6% of their monthly income.

US researchers studied the performance and economic losses caused to dairy farms in different parts of the country. Their findings show that cows in the coldest state suffer heat stress for 6% of year time, lose 270 kg milk production and 80 US$ income annually, while those in the warmest state, suffer heat stress for almost 50% of year time, lose 1800 kg of milk and 680 UD$, annually.

When dealing with Europe, we have to take in account the differences between different regions (Continental climate in central and east Europe, Maritime in the Atlantic and North Sea coasts, and Mediterranean, in South Europe). As can be expected, summer negative impact on the cows will be different in each of these regions.

THI threshold for cows in West Europe is 65, which is 3 THI units below that characterized for cows in warm climates, including European Mediterranean coast. The reason for that is the fact that these cows are less adapted and genetically inferior to cows raised in warm climates. Cows in temperate regions are unable to recover from the negative effects of HS, as quickly as cows raised in tropical or subtropical climates.

Heat mitigation is required to help cows overcome heat stress. Before talking about activation of heat mitigation means, there is a need to prevent external heat load by providing cows sufficient shade and expose them, as possible, to natural winds. Heat mitigation means can be classified into two main modes. The first is “Direct cooling” (cooling the animal), which includes wetting, forced ventilation and in most cases, the combination of wetting and forced ventilation. The second is “Indirect cooling” (cooling the environment), which includes high-pressure fogging and evaporative panels, which is mostly in use in dry climates. In some extreme cases, the combination of direct and indirect cooling systems is in use. Cooling by a combination of wetting and forced ventilation is the most common system in use today. We assume that more than 80% of world dairy farms, which cool their cows, are using this method. Such cooling system can be provided in farm “waiting yards” (before and between milking sessions) and in “feeding line” (after and between milking sessions). In the “resting area”, only fans are in use, in order to prevent wetting resting area surface. It is important to know that forced ventilation can dissipate the metabolic heat generated by a dry or a low producing cow (< 15 kg/d), but is not capable to dissipate the metabolic heat, generated by medium and high producing cows (> 20 kg/d). Combining wetting with forced ventilation is highly recommended for cooling the cows, as it is relatively cheap and easy to use, and above all, have the potential to dissipate 5 times more cow’s heat than forced ventilation or wetting alone.

There is a difference in “cooling needs” for cows located in different world regions. In Tropical regions, cows need cooling all year around (S.E. Asia, Caribbean Islands and Central America). In Sub-tropical regions, the need for cooling is for part of the year, ranging between 3-8 months (Israel, South USA and Mediterranean coasts Europe). In Temperate regions, the need for cooling is for only 1-2 months per year and in many cases even not necessarily, along all this period of time and only during heat waves (West Europe, Canada, and North USA and China).

When dealing with cooling the cows in Germany, we have to take in account the advantages and disadvantages, as compared to warm climate regions. The advantages are, less “stressful days” per year, less stressful hours and relatively cool nights in the summer. The disadvantages are, being the cow less adapted to heat load, barns less suitable to warm conditions and lack of knowledge and experience of farmers on how to install and properly operate heat mitigation means.

In recent years, more knowledge start being accumulated, regarding the negative effects of heat stress on cow performance in Germany, and dairy farmers are facing declines in the performance of the cows in the summer. When coming to heat mitigation, then most of the knowledge that exists today regarding the operation of heat mitigation means comes from warm regions like Israel and the southern United States, and very little knowledge (if any), exists today on cooling the cows in temperate climates. It is important to have this specific knowledge, since the characteristics of the summers in temperate cool regions (short periods of heat waves, and cool periods in between), is different from summers in warm climates (continuous warm periods, lasting for 3 – 12 months per year).

In light of this, in my opinion, there is a need to carry out field studies in the coming years in Germany and temperate climate countries, where the following topics will be studied:

- The “effectiveness” of actual forced ventilation equipment installed in resting and feeding areas.

- The Implementation of “conventional” cooling system, in use today (combining wetting and forced ventilation), which will be operated at different intensities (accumulated hours of cooling per day). In Israel, we cool the cows for six cumulative hours per day and maybe it is “too much” in Germany.

- Compare the results reached when cooling the cows is done in a continuous form all summer period (30 – 60 days per year), like is done for longer periods in warm climates, to those, when cooling the cows before and during the heat waves (making use of forecasts coming from regional meteorological stations).

It is expected that the information gained in these studies will have an important impact on the optimization of the use of heat mitigation means and prevention of drop in cow’s performance in the summer in the temperate and relatively cool parts of the world, among them, Germany.

Making use of a special Excel spreadsheet, which I developed almost 20 years ago, I calculated the theoretical cost-effectiveness of implementing cooling means in Germany, assuming that the system will operate continually for a period of 60 summer days. We assumed per cow investment in cooling equipment of 150 €, and operation cost of 15 € annually. Running the program with expected improvement in annual per cow milk production of 2 to 5 % show an expected increase in per cow income, ranging between 25 and 95 € annually. It is worth nothing that in case research will indicate obtaining same improvement when using the cooling system less intensively and spending less water and then the economic benefit will be even greater.

In conclusion, due to climate changes and the increase in per cow milk production, German and temperate climate farmers in general start facing drops in cow’s performance and economic losses in the summer. The situation is expected to be aggravated from now on. It is now the time to start “taking action” by making use of knowledge and experiences gained already in warm climates, adapting them to their “type of summer “ conditions and farming system, which will lead to its optimization.