“There are no more mid-seasons!” How many times do we hear it?
In fact, over the last 50 years, global temperatures have seen a significant spike and the lack of laws and regulations capable of countering this trend seems to be able to cause a further increase of +1.5°C by 2030-2050.
Let’s now examine the effects of increasing global temperatures on dairy cow welfare.
The effect of Global Warming has a significant managerial and economic impact on the primary sector, especially in agriculture and livestock farming.
The dairy cow is very susceptible to temperature changes.
As a matter of fact, the thermal comfort zone of dairy cows ranges from -5°C to 25°C, with slight variations depending on the physiological and productive state of the cow itself.
The negative effects of heat stress on cows can be divided into three categories, and it is important to highlight that these do not stop with the lowering of temperatures but can have effects for shorter or longer periods (see table on the side).
The exceeding of the thermal comfort zone in dairy cows is due to a combination of environmental factors (increased temperatures, relative humidity of the air) and the inability to stay cool. The combination of temperature and humidity can be measured through an index called THI – Temperature Humidity Index that allows defining stress thresholds in cows.
Is it possible to select for heat tolerance in dairy cow?
Several studies in the past have highlighted significant differences in sensitivity to heat stress between breeds and species. In particular, in the case of dairy cows, some researchers estimated genetic correlations ranging from -0.23 to -0.41 between resistance to heat stress and productive and reproductive traits (Ravagnolo et al., 2000, 2002).
This means that the exclusive selection for productive traits tends to select animals that are more sensitive to heat and humidity. Improving the functional traits of the herd will therefore indirectly increase the level of heat tolerance of the animals.
In December 2017, the first official index for heat stress resistance was published in Australia, a topic that soon became one of the objectives of the LATTeco project by ANAFIBJ. With the data release of April 2022, there will be significant news on this topic!