The summer heat stress is one of the largest causes of economic losses to dairy farms in the world. In particularly hot regions, a drop of more than 1,500 liters par lactation from cow’s potential is reported, with a loss in potential annual net income of about $ 600 per cow. Optimizing cow cooling can reduce the annual production loss to less than 200 liters, and the financial loss to almost $ 100, improving per cow profitability by 500 $, annually.
In recent years, we started using intra-vaginal data loggers to evaluate the effectiveness of the cooling treatments recommended to the dairy farms. The intra-vaginal data loggers are inserted into the cow’s vagina by using CIDR device, originally used on TIME IA protocols. To start using this technology, data loggers are “activated” through special computer software and inserted into the cow’s vagina by special applicator. Data loggers are usually placed in a sample group of cows comprising of about 10% of the number of cows in the group and remain in the cow’s vagina for 24-72 hours, at a reading frequency of every 10-15 minutes. After that time, data loggers are pulled out and information is downloaded into a graphical software that shows the findings (see pictures below).
The use of data loggers in the dairy sector began in Israel about ten years ago and, since then, its use has expanded considerably. I use this technology in each of the projects I am involved, in different parts of the world. Usually, data loggers are used to characterize the current state of the farm in coping heat stress and to provide recommendations for installation and operation of cooling means. Subsequently, this technology is used to monitor the effectiveness of cooling means, already in operation, and make adjustments and improvements to obtain the best result possible.
The way data loggers allow us to improve cooling treatment and achieve better results is presented by the two figures below, taken from a project I did with large dairy cooperative in northern Mexico. The data is taken from a dairy farm with 3000 cows and high production level. In summer 2016, “special cooling yards” were built in the front of the waiting yard, so cows could be cooled combining wetting and forced ventilation for one hour, before each milking session (a total of 3 cumulative hours per day).
As shown in Figure 1, it can be seen that cooling the cows every 8 hours did not allow cows to maintain normal body temperature throughout the day, and cows spent a great part of the day above 39 C. In contrast, as can be seen in Figure 2, cooling the cows for 6 cumulative hours a day (as I currently recommend), and at intervals of no more than 4 hours between one cooling session and another, completely prevented the increase in cow’s body temperature, so cows could be in thermal comfort conditions 24 hours a day.
Due to the intensity of the cooling, the conception rate to inseminations provided in summer 2016 (June - October) was more than 30%, and did not differ from the conception rate in winter months, as compared to conception rate of around 15% in same summer months in 2013-2015. The average daily milk yield per cow in this farm was 4 liters higher in summer 2016, as compared to previous summers.
Based on my experience in recent years using data logger in projects I am involved in various countries, I can say that the results obtained in north Mexico are close to the maximum that can be obtained from cooling treatment in commercial farms. In most cases, as can be seen below, there is a difficulty in such farms, with high level of milk production and warm climate, to achieve complete prevention of the increase in body temperature, as we have achieved in Mexico.
Recently, a group of researchers from the Israeli Agricultural Research Organization conducted a survey in 18 dairy farms in Israel with an annual yield of 12,000 kg or more, located in different parts of the country. In each farm, the vaginal temperature of 32 cows was monitored, over two 72-hour periods and twice per summer (July - September). To the findings of the above mentioned survey, I have added data from the “summer to winter ratio report” that is produced every year for every farm in Israel. The farms in the survey were divided into 3 different groups, based on the number of hours throughout the day where cow’s body temperature exceeded normal. The results are presented in Table 1.
From the data presented in table 1 it can be clearly seen that, under Israeli conditions, no farm out of the 18 studies could maintain its cows in normal body temperature throughout the entire day in the summer. It can be also clearly seen is that there is big variation between farms in the number of hours per day cows suffer heat stress. The explanation to this variation can be an extremely high level of production in some of these farms (close to 14,000 kg annually), the degree of heat stress in the region farm is located and insufficient intensity of cooling procedures used in the specific farm. Cows in the farms of the “short time” group (where cows probably received the best cooling treatment), spent an average of 4.3 hours per day in heat stress and no more than 5 hours per day. The cows in “long time” group (where probably poor cooling was provided), spent in an average 9.2 hours a day in heat stress, more than double the time of the “short time” group cows.
The “summer to winter ratio” for milk production (an index calculated in Israel for every farm at the end of each year), averaged 0.96 in the “short time” group herds, compared with the ratio of 0.92 in the “long time” one. Conception rate to first inseminations done in summer months were 43% and 30% in the “short time” and “long time” farms, respectively.
Conception rate to all inseminations in same farms were 33% and 21%, while the gap between winter and summer conception rates between 12 and 20 percentage units in these farms, respectively.
It must be taken into account that the numbers presented in the table above, are only averages and hence indicate only a trend. Within each group there is a minority of exceptions. In the “short time” group, there are a limited number of farms with relatively low summer performance and, on the other hand, farms with relatively good summer performance in the herds of the “long time” group. It must be understood that the number of hours a day in which body temperature of the cows is above normal does not necessarily indicate their ability to achieve a good level of performance in the summer.
The conception rates to the first and to all inseminations were significantly higher in the “short-time” group compared to the other two groups. However, even in this group, the conception rates reached in the summer was 12 percentage points lower than those obtained in the winter. Throughout the years in which we elaborate the “summer to winter ratio” report in Israel, we have not seen yet conception rates in the summer, similar to those obtained in the winter, even when it comes to farms with a summer to winter milk production ratios of 1.0, or close to it.
It is true that in our project in Mexico, the cows maintained normal body temperatures throughout all the day in the summer and, in same time, a summer conception rates of above 30%, similar to those obtained in the winter. Anyhow, these numbers were 10-15 percentage units below those expected in commercial farms in the winter. Most probably, the cows in this farm suffered from relatively low fertility traits, due to reasons which were not related to summer heat, that limited them to fulfil their conception potential in both, winter and summer. The only case where high summer conception rates could be achieved, was in an experiment we conducted in the middle of the eighties in the experimental dairy farm of the ministry of agriculture in Israel. In this study, intensively cooled cows were capable to maintain normal body temperatures throughout all the day along all the summer and reached summer conception rates of 50%, similar to those obtained at that time, in commercial farms in the winter. Unfortunately, since that study, no such results could be reached in commercial dairy farms in Israel.
The increasing number of commercial farms in Israel and the world, using data loggers as a management tool, can give us the opportunity to improve and optimize the cooling treatments provided to the cows. From one side it will allow us to verify if, in cases of achieving normal body temperature throughout the day in the summer allows them reach conception rates of 40% and more in the summer, as they do in winter, and evaluate if the investment required to reach this goal is economically justified. From the other side, confirming the possibility of obtaining milk yield in the summer, similar to those achieved in the winter, even when cows spend several hours per day beyond the normal temperature, can have its economic importance, as it will allow us set the time limits for cooling, allowing economic optimization of the cooling process.