The dairy industry is important for economic and food security in most countries of the world. Millions of producers around the world raise about 280 million dairy cows and produce close to a billion tons of milk a year. Global economic expansion in the last fifty years is reflected in lifestyle changes in many countries, which are also reflected in the increase in demand for milk and its products, and this is especially true for “emerging countries”. Global milk consumption is expected to increase by about 60% by 2050, mainly in China and Southeast Asia, with many new consumers and governments promoting milk consumption through dietary guidelines and school milk programs.
China is currently the largest importer of milk in the world, and recently imported a quantity of milk that is 120 times larger than that imported in the 1960s. Milk imported to China today accounts for almost a third of the country’s total milk consumption and the Chinese government is making great efforts to increase domestic milk production and reduce that imported.
There are clear signs that the growth of milk production in China is stabilizing, and recently there have even been reports of a decline. Heat stress is one of the main reasons for the reduction in milk production in China. This is due to global warming on the one hand, but mainly due to the increase in per cow yield, which means an increase in the amount of metabolic heat produced by the cows and should be dissipated to the environment. Between 2008 and 2016, the extent of the decrease in daily yield per cow in the summer, as compared to the winter, increased from 0.7 to about 4 kg per cow per day. It is expected that if this trend continues, and no management measures taken, the decrease per cow will reach 6.5 and 7.2 kg per cow, in 2050 and 2070, respectively.
For the past twenty-five years, I have been giving lectures on how to cope with heat stress, to Chinese professionals, in the framework of courses held in China and Israel. I was recently invited to give a virtual lecture for the technical staff and managers of the large dairy farms of a Chinese dairy company, which is one of the three largest dairy companies in China and among the twenty largest dairy companies in the world.
As I do before giving lectures to people from different dairy industries in the world, I addressed the company people before the lecture, and asked them to fill out questionnaires that would allow me to examine the state of milk production in their farms, from the aspect of summer impact on cow performance and production. Most of the dairy farms that supply milk to the company are located in northern China (temperate climate and few warm months a year), but the company also has dairies and dairy farms in southern China (hot tropical climate and multiple months of the year). To get a picture of the effect of summer conditions in the two regions, I asked for and received data of two dairy farms, with about 3000 cows in each, one located in the north and the other in the south. Based on the questionnaires and Excel forms, filled out and sent back to me, I was able to draw graphs and examine the extent of the effect of summer heat in both regions. Chinese dairy farmers, like their counterparts around the world, have been exposed in recent years to knowledge about how to install and operate means for cooling cows, and every year they are getting better. The data sent to me from both regions and presented in this article describe a snapshot for 2021. According to the reports submitted by farm managers, cows in both farms were cooled in summer of 2021 by a combination of wetting and forced ventilation, given to cows in the waiting yard before each of the three milking sessions, and in the feed line, when cows return from milking parlor, as well as in feed line, between milking sessions. Cooling treatment was given to the cows in lactation, dry cows and late pregnant heifers.
The daily milk yield per cow in different months of 2021, in the two dairy farms is shown in Figure 1. The average number of days in milking in same periods is shown in Figure 2.
Figure 1 - Daily milk yield per cow (kg) in the different months of the year 2021 in dairy farms located in northern and southern China.
Northern = Blue, Southern = Orange
From the presented in figure 1 one can clearly see the decrease in the average yield per cow in cows from both farms. As expected, the decline is greater in the southern farm, as compared to the northern one. Cows in the northern farm decrease in summer by 15% in milk production, as compared to the winter, while a 40% decrease was observed in the southern farm.
It is worth noting that the average summer to winter ratio of all dairy farms in Israel is of 0.95, and the ratio in those farms that fail in coping with summer heat stress is 0.85 (like that of the farm in northern China, where summer is usually “lighter” than in Israel).
Figure 2 - Average “days in milk” (DIM) in different months of 2021, in dairy farms located in northern and southern China.
Northern = Orange, Southern = Blue
The data presented in figure 2 explains great part of the decrease in the daily yield per cow, observed in figure 1. The average number of days in milk in the two farms was relatively low in the winter months and increased considerably in the summer months. This is probably due to the decrease in cow’s conception rate in inseminations given in the summer. Here, too, as expected, the gap between the seasons is greater in the southern farm, and also the absolute number of days in milk is greater in this farm, explaining, at least in part, the gap in the extent of the summer decline between the two regions. In any case, it is interesting to see that even in a relatively comfortable climatic region, like northern China, with short summers and cool nights, there is a marked decrease in cow performance in summer, nothing to talk about cows in the south! The data presented in this article indicate that, although the knowledge and experience gained by farm managers in properly cooling the cows and despite the large investment they make, by installing and operating cooling equipment, the results are still poor, and cause the farms heavy economic losses every year.
Here comes the interesting and important stage in my consulting work, which I hope will start with the Chinese company soon. This is, to find out what was done wrong, which prevent farms reach the expected results. Is it the quality of the wetting?, the intensity of the ventilation?, the total hours per day, cows receive the cooling treatment and its distribution during the day?. Are the cows overcrowded?, are the cows exposed to direct and indirect solar radiation, and if so, a for how many hours a day?, do cows have sufficient space in feed manger and water trough? Are food and water served properly? Next, comes the testing phase of physiological and behavioral parameters, such as monitoring body temperature and respiratory rate during the day (if possible, using tools already available today in most dairies and farm management software). Only after receiving the full picture, comes the recommendations phase and follow up program, until the expected result are achieved.
From my experience in many projects I have done in different parts of the world, I have learned what a “proper cooling” is, and that success or failure depends on the small details. We know today what needs to be done, in order to give cows a proper and adequate cooling treatment, and significantly reduce the decline in cow’s performance and the economic losses in the summer, all described in the various articles I have published. I hope that Chinese company management will “lift the glove”, so we can achieve these good results with them as well.