This article presents the results of a "cow cooling project", in northern Mexico, characterized by long hot and dry summer months, with the extreme conditions of heat stress in dairy cows. The farms where the cooling project took place are considered as large scale dairy farms, with high-yielding cows from the Holstein breed. The dairy farmers are aware of the existence of a negative effect on the indices of summer production, reproduction and health of the cows and the economic losses caused to them and show a great willingness to take the necessary actions and spend what it takes, to deal and solve the problem.
Summer 2014 was the first summer of the project, set to "Summer Learning", which explored the best way of activating the cooling conditions in the barns. The findings from the first year helped us to establish the "strategy of cooling" for the dairy farms in the region and implemented in large scale dairy farms (1200 to 3600 dairy cows per farm, milking 3 times per day for a total of almost 21 hours), in summer 2015. One of the limitations for cooling cows in these farms is the fact that milking parlors there have high speed milking capacity and therefore, the duration of cows to be cooled in the waiting yards before each milking sessions is very short and do not allow provide cows the time needed for proper cooling. The cooling in the feeding line of these farms is also limited, mainly due to side winds in a large number of hours a day, which negatively affects fans and sprinkler systems.
The cooling solution we have reached for this kind of farms was to build "special cooling-yards", placed near the waiting yards and milking parlor. These special cooling yards were used as sites where cooling treatment can be extended for all the cows around milking time (before and after milking sessions), as well as to cool the milking cows between milking sessions.
In summer 2015, we implemented this concept, combining cow cooling by wetting and force ventilation in the special cooling yards and waiting yards, in five large scale dairy farms in the region. Cows were cooled for 6 cumulative hours per day, 3 treatments of one hour before and after each milking session, and 3 times of one hour each, 4 hours after each milking session. Each cooling session consisted of fans operating continuously and wetting for 30 seconds every 5 minutes. To monitor the effectiveness of cooling, we used "vaginal data loggers" inserted to a sample of representative cows, throughout the summer.
Following, some pictures from the cooling sites in the project farms.
The climatic conditions prevailing during the summer of 2015, expressed as number of hours a day with different THI (Temperature Humidity Index) values are presented in Figure 1.
Figure 1 - Average number of hours per day with different Index of Temperature and Humidity values in 2015, in northern Mexico (black line represents the number of hours a day with the heat load over the value of 68 which is considered as a heat stress borderline).
From the presented in Figure 1, it can be seen that in the regions where the project took place, temperature humidity index values above the critical level recorded for 24 hours a day in four months per year (June - September), when in March, April and October, Heat stress conditions prevailed over the critical level in part of the daytime.
Milk production -
The intensive cooling the cows in the project farms in summer 2015 contributed to a significant reduction in the drop in production, which occurred in previous years, when no cooling was provided to the cows in the summer.
Figure 2 describes a typical lactation curve (monthly averages of per cow daily milk production), in a 3600 cows dairy farm participating in the project). As can be seen, lactation curve for the period between 2011 and 2014 is where no cooling was provided, is significantly inferior to that of 2015, with intensive cooling.
Figure 2 - Average daily milk production per cow (liters) in a typical dairy farm, intensively cooling the cows in summer 2015.
The ratio between the milk produced in the winter months (January - March) and summer (June - August) in the 5 dairy farms in the project is presented in separate for the years 2011 and 2015 in 2011 is presented figure 3. From the presented in this figure, it can be seen that the gap in production between winter and summer averaged 4.6 liters per cow per day in 2011 and dropped to only 0.7 liters per cow per day in 2015. The average summer to winter production ratio was 0.87 in 2011 and rose to 0.98 in 2015, which means that summer drop in milk production almost disappeared in the year when cows were intensively cooled.
It should be noted that the results obtained in the project in Mexico, are quite similar to the results obtained in a survey conducted with the ICBA (Israel Cattle Breeders Association) and published internationally in 2003. In our survey, we compared the average daily milk production in dairy farms with minimal cooling the cows in summer as compared to those that cooled their cows intensively. Milk production of cows in farms with minimal cooling in the summer (July - September), dropped by 3.5 liters per day, compared to the winter months (January - March), and the summer to winter ratio of milk production was 0.89. In contrast, dairy farms with intensive cooling in the summer, dropped by only 0.6 liters per day between the two seasons and summer to winter production ratio reached 0.98.
Figure 3 - Average daily milk production per cow (liters), in winter (January - March) and summer (June - August), in farms which intensively cooled the cows in 2015.
The conception rate was chosen as a representative parameter to evaluate cooling effect on cow's reproductive performance. Conception rate to inseminations given in the summer of 2015, when cows were intensively cooled, was significantly higher in all the farms of the project, as compared to that obtained in summers of 2011-2014, without cooling the cows. The conception rates from all inseminations given in summer months in the typical farm, its production data presented above, are shown in Figure 4.
Figure 4 - Average conception rate (%), in a typical dairy farm, intensively cooling the cows in summer 2015
Figure 5 - Average monthly conception rate (%), in inseminations given in the winter (January - March) and summer (June - August), in farms which were intensively cooled in summer 2015.
Similar to the described for the production of milk, also, when it comes to fertility, the results obtained in the project in Mexico in summer 2015 are quite similar to the results of the survey conducted in Israel, where we also examined the effect of cooling on cow's fertility. Conception rates of inseminations given in winter months in Israel did not differ between farms with minimal or intensive cooling in the summer (near 45%). In difference from the inseminations given in the winter, conception rates of intensively cooled cows in summer 2015 was almost double of that reached in farms with minimal cooling (34% and 17%, respectively). The summer to winter ratio for conception rate was 0.72 and 0.40, respectively, in farms with intensive and minimal cooling in the summer.
What are the factors that contributed to achieving the good results in our project in Mexico?
In my opinion, summer 2015 was for the first time in the history of that region that cow's cooling procedures met the needs of cows, This includes the following:
- Cows were force ventilated and wetted in the recommended intensity and quality, according to the recommendations.
- "Space per cow" in the cooling sites was sufficient in order to prevent crowding and allow cows have proper cooling.
- Cows were provided sufficient "cooling time" during the day, through the entire summer.
- Cows were cooled many times per day (once every 4 hours), including at night time.
- Measurements of vaginal temperatures indicated that cows were in "thermal comfort", in most of day hours.
- Cooling treatment started gradually in late spring and ended in the same manner in late fall.
- Fresh foods and sufficient clean water were offered to the cows freely along all the summer days.
The economic aspects of cow cooling -
The Implementation of the cooling means in this project would involve considerable financial investment, for installing and running the cooling system.
In general, the investment in equipment for the construction and installation of cooling equipment in the special cooling yards ranged between $ 400,000, in relatively small dairy farms, to $ 800,000, in the largest ones (investment ranges from $ 200 to $ 250 per cow).
Running the cooling system during 150 summer days costs about $ 45 per cow, of which $ 30 for electrical power, $ 10 for manpower (six additional employees were hired and worked in three shifts per day), with the remaining costs (mainly maintenance) were $ 5.
Using a special computer program that I developed together with an agricultural economist from the Israel Dairy Board, I examined the cost-effectiveness of cooling cows under Mexican conditions. The software takes into account, on one hand, the investment required for properly cooling the cows (investment in equipment and operating costs). On the other hand, we took in account the additional annual milk produced per cow, the decrease in "days open" and the improvement in "feed efficiency" (conversion of feed to milk), as were obtained in these farms in summer 2015. Among the benefits raising from intensively cooling the cows I calculated a 10% increase in per cow annual milk production, 5% improvement in "feed efficiency", for 150 summer days and a decrease of 5 "open days" annually, with a value of $ 5 per day, due to the improvement in conception rate of cows inseminated in the summer.
I conducted the study for a dairy farm with 3000 cows, investing $ 800,000 to install the cooling system. The results of my calculation show that under the conditions mentioned, and actualized prices of inputs and outputs in Mexico, the additional income per farm due to the implementation of cooling the cows reached $ 200 per cow per year and $ 600,000 annually to the farm. Under these conditions, investment payback can be reached in less than two years.
World dairy industry moves towards the establishment of large scale dairy farms with high genetic merit cows in new regions, mostly in warm parts of the world and close to the centers of consumption. The knowledge and experience we gained in this project in Mexico, as well as similar projects, in Israel and other warm regions of the world, will help us cope with the problems caused by heat stress in these regions in the future.