Protection from direct and indirect solar radiation - an important factor for dairy cows in summer

In a previous article that I recently published, I dealt with the importance of drinking water and water for cooling the cows, when dealing with the summer heat. In this article, I would like to deal with another factor that I see as very important in the above-mentioned confrontation, and it is shade, or in other words, preventing the exposure of cows to direct and indirect solar radiation in the summer.

Why is it important to protect cows from solar radiation in the summer?

To understand the answer to this question, one must first know the “heat balance” of the cow. To function normally, a cow must have its heat production equal to its heat loss. Otherwise, the cow will enter a “heat stress”, which will be manifested by an increase in body temperature and a series of behavioral and physiological events, the result of which is impaired performance. A cow that produces 45 liters of milk a day generates about 2,000 watts of heat, which it needs to be dissipated into the environment. In winter, when the ambient temperature is lower than the cow’s body temperature, heat is lost spontaneously and there is no problem. In the summer, when the ambient temperature is equal to or higher than that of the cow’s body, the same “spontaneous loss” is not possible, and the “panting” mechanism, the only one that can still help it, is not enough to dissipate the heat produced. If we now add to this the solar radiation. This “contributes” to the cow external heat, to the extent of close to 1,600 watts, which brings the cow to the need to dissipate 3,600 watts, a completely impossible task. Studies done on cows in pastures in temperate regions, showed that the cows can enter into “heat stress” already at temperatures of 18 degrees. That is, their heat production plus the heat from solar radiation exceeds their heat dissipation capacity. The conclusion from this is that high yielding cows in the summer have no chance of maintaining their body heat without “external intervention”, hence the importance of preventing exposure to solar radiation by providing shade and protection means.

In this article I will deal only with cows that are in full housing conditions, having the possibility of being in the shade during the day. If so, where can the cow be exposed to the sun’s radiation?

Well, there are several sites where the cow may be exposed to direct or indirect solar radiation during the day and I intend to present them in text and pictures in this article.

The first site is the barns themselves. The placement direction of the barns is closely related to the extent of the sun’s penetration into the structure. The optimal placement direction in the Northern Hemisphere is when the longitudinal axis of the building is in the east-west direction, and in this axis, the extent of penetration of solar radiation into the building is the lowest. In the internet network, there are currently applications, some of which are free, that allow planners of a new barn to examine the best placement direction, with reference to the geographic location of the farm. It is recommended for those planning the construction of a new dairy farm to use such software.

The second site is the feed manger. Cows spend several hours a day in the manger for eating and being cooled, and sometimes they are also locked during this time. In mangers facing east, sun penetration is expected in the morning, in those facing west, the penetration will be in the afternoon, and in barns facing south, penetration may be for several hours in the middle of the day.

Well, so what can be done?

As can be seen in the following pictures, one can use curtains that will prevent the penetration of solar radiation, among them, large scale farms, as well as farms marble barns, as well as small family farms in northern Italy.

Picture 1 - A “net curtain” as a shield against the penetration of solar radiation into the manger in a large dairy farm in southern Italy.

   

Picture 2 - A movable curtain as a shield against the penetration of solar radiation into the manger in a family small dairy farm in north Italy.

In some dairy farms, shading is provided by means of a “visor curtain” as can be seen in the following photo, which is also a customer from northern Italy.

Picture 3 - Shading of the manger using a “visor” curtain in a barn in northern Italy.

A third site for shading is the water troughs. Although the amount of time per day that the cows spend at this site is short, solar radiation at this site, beyond the direct effect on the cows, also has an effect on the warming of the water and the development of algae in it. Providing shade in the area of the water troughs should include the trough itself, as well as the area near the trough, where the cows have to stand.

Picture 4 - Shading of troughs in a dairy farm in north Israel.

A fourth site for shading is the “walkways” leading to the milking parlor, or to the special cooling yards. The problem is mainly in large scale farms, where cows must walk long distances in order to be milked or cooled, and hence also the duration of exposure of the cows to the sun radiation. In the following photos, one can see shading nets, installed over walkways in large scale dairy farms in Turkey and Mexico.

Picture 5 - Shading of the walkway to the milking parlor in a dairy farm in southern Turkey.

Picture 6 - Shading of the walkway to the milking parlor in a dairy farm in north Mexico.

It is possible and even desirable to add water troughs along the walkways. Usually, cows prefer to drink water immediately after being milked and the installation of water troughs along the walkways allow the reduction of competition for access to water in the group and allow more cows to consume water at the time when they are most interested in it. In the picture below, we can see such water troughs, installed in a dairy farm in a desert region in south of Israel.

Picture 7 – Water troughs installed in the walkways to the milking parlor in a farm located in the south of Israel.

The last site where it is appropriate to protect cows from solar radiation (mainly indirect) is the waiting yard (or alternatively, a cooling yard). In these yards, the penetration of solar radiation is particularly problematic, since the cows are crowded inside the yard without much ability to move. As can be seen from the following picture taken in a dairy farm in southern Italy, a curtain or shade net can be installed in both sides of the yard, in such a way as to prevent solar radiation from penetrating into it. These curtains may also have a contribution in “blocking” the penetration of natural wind that comes perpendicular to the direction of the fans inside, which may reduce the strength and speed of the wind created by fans there.

Picture 8 - Plastic curtains for shading and preventing the penetration of solar radiation into the waiting yard in a large scale dairy farm in southern Italy.

In conclusion, providing shade and preventing exposure of the cows to direct and indirect solar radiation is of great importance in ensuring the thermal comfort of the cows and thus, ensuring the ability of the cows to realize their genetic potential. Before we look at how to dissipate the heat generated by the high yielding cows through cooling, it is appropriate to ensure that they do not overheat from the sun.