Stages in the development of the cooling system, based on wetting and force ventilation

Cooling the cows through a combination of wetting and forced ventilation is the most common method in the world today. I estimate that more than 80% of the cows that are currently cooled in the world are cooled by this method. Today we know very well what is required to cool the cows properly, in terms of the "wetting quality", air speed and the time required for cooling during the day and throughout the year.

In this article, I would like to describe how was developed the knowledge on which we base today the recommendations for cooling the cows we give to dairy farmers all over the world.

The first scientific documentation of the development of the cooling method that combines wetting and forced ventilation is from almost 80 years ago. Researchers from the University of Louisiana (Seath & Miller, JDS 31:361, 1948), kept cows in the sun for two hours and then placed them in a building where cows received a treatment of wetting by a garden hose, or wetted and forced ventilated by household fans. As expected, the combination of wetting with forced ventilation tripled the heat loss from the cows, compared to wetting alone. Cows that received cooling that combines wetting and forced ventilation returned to normal body temperature in half the time required for cows that were only wetted.

The next step in the development of the method was within the framework of my doctoral thesis conducted in Israel, in the early eighties of the last century. The purpose of the thesis was to examine the effect of such type of cooling, given to dry and milking cows, on their productive and reproduction performance. As a preliminary step in the research, we were required to optimize the cooling treatment in terms of the duration of the wetting (we compared 10, 20 and 30 seconds), and the duration of the cooling treatment (we compared 15, 30 and 45 minutes), while wetting was given once every 5 minutes (Flamenbaum et. al. JDS 69:3140, 1986). The test findings showed that the best cooling is achieved when the cows are wetted for 30 seconds every 5 minutes, for a treatment duration of 45 minutes. Cooling the cows in this format, four times per day (one every 6 hours), made it possible to find the cows in thermal comfort (body temperature below C 39), throughout the entire day, as compared to cows in a parallel group without cooling that, found with a body temperature above C 39 during most of day time.

The next step in the development of the method was conducted at the beginning of the 2000s by researchers from the University of Kansas (Brouck et. al 2002 and 2004). The researchers examined the optimal wind speed while comparing speeds of 1, 2 and 3 meters per second and found that the highest speed tested, combined with wetting, gave the best cooling results. Later on, these researchers examined the optimal wetting frequency (wetting every 5, 10 and 15 minutes, with continuous ventilation), and found that wetting every 5 minutes gives the best result (similar to what we found in Israel, nearly 20 years before).    

Over the years, the need to cool the cows has increased, due to global warming on the one hand and the increase in cow's milk yield, which means more heat production, on the other hand. The time intervals between the cooling treatments that were given in the early 1980s are no longer relevant today and an increase in the frequency of "cooling sessions" is required, as well as the addition of cumulative "cooling hours" per day.

In the last decade, intravaginal data loggers have been put into use in many dairy farms around the world. Day long monitoring of cow's body temperature enables evaluation of the effectiveness of the cooling treatment given to the cows to identify periods of time when the cows are suffering heat stress, and adjust the duration and frequency of the cooling treatment provided, with the aim of preventing the cows from being heat stressed at all hours of the day. Recently, intravaginal data loggers which can remain in cow's body for a long time and transmit her body temperature continuously and online became a reality. Expanding the use of these means in dairy farms will significantly advance the dealing with the heat load, and at the same time, help optimize the use of the above mentioned cooling means.

In one of my first projects, carried out with this cooling system, in a large scale 3,000 cows dairy farm, located in northern Mexico. Initially cows were cooled for an hour, before each milking (that's 3 cumulative hours of cooling per day). By using intra vaginal data loggers we found that cow's body temperature was above 39 C (considered a threshold value), in most of day time. When we doubled the number and duration of cooling sessions (6 cooling treatments of one hour each, and a total of 6 hours a day), cow's body temperature was maintained below 39 C for the entire day.

In parallel to my project in Mexico, a group of researchers in Israel (Honig et. al. 2012, JDS 95:3736), examined the effect of cooling the cows by the combination of wetting and forced ventilation for 3.5 and 6 cumulative hours per day (5 and 8 cooling sessions of 45 minutes each). The cows that were cooled for 6 cumulative hours per day consumed 2 kg of dry matter per day more and produced 3.4 kg more milk, as compared to those cooled for shorter time. At the same time, these cows rested and ruminated for a longer time in the day.

Here we come to the bottom line:

Optimal wetting of the cows every 5 minutes in combination with forced ventilation at a wind speed of 3 meters per second, provided in 45-60 minutes "cooling sessions", provided for 6 cumulative hours per day (once almost every 4 hours), allow cows to maintain normal body temperature along all summer, for all that it implies for cow's welfare and performance.

To confirm this statement, I would like to bring data from Israel, where we developed the summer: winter ratio index more than twenty years ago. (Flamenbaum and Ezra 2007, JDS 90:345). Cows in dairy farms that received the cooling treatment presented earlier, reached in the summer 98% of their yield in the winter, this compared to only 88% in dairy farms with less intensive cooling treatment. The conception rate in inseminations given in the summer in those farms with intensive cooling was lower in 10 percentage units, as compared to the conception rate in winter, this compared to a summer decrease of 30 percentage units and more, in dairy farms where cooling was not applied in this intensity. (Flamenbaum and Galon, 2010, J Rep. and Dev, 56:536 ).

Using economic software, which I developed several years ago, shows that the investment in installing and properly operating the cooling system, as recommended, can be paid back in less than a year. Intensive cooling of cows can increase the annual income per cow by 100 to 200 US$ per year, in dairy farms located in temperate regions, and between 1,000 and 1,500 US$ per cow per year, in dairy farms located in warm regions (depending on the climatic characteristics and the production level in each farm). Intensive cooling of cows in warm regions may reduce to 20% the economic loss that would have been expected without cooling.

Dear farmer, now you know what needs to be done, and how to do it right. From here on, things only depend on you!