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Nutritional strategies to mitigate heat stress of dairy cows
Dairy cows are in their comfort zone when the temperature- humidity index (THI) is lower than 68, which corresponds to a combination of temperature and relative humidity below 26°C and 45%, respectively. However, these conditions are hardly maintained all along the year in hot or tropical areas.
T
emperate regions are also facing increasing extreme hot temperature-events because of climate change and related increasing world temperature, pushing the cows outside of their thermoneutral zone of comfort.
Performances of dairy cows subject to heat stress may be severely affected. Milk yield decreases linearly by 3 to 4 kg/d per 20 additional points of THI (Bernabucci et al., 2010). Cows with high potential milk production are even more affected as increasing milk production from 35 to 45 kg/d reduces threshold temperature for heat stress by 5°C (Berman, 2005).
Heat stress can also affect reproduction performances (Rensis and Scaramuzzi, 2003). The lack of energy as a result of lower intake, lower energy metabolism and higher energy spent to maintain body temperature compromises the uterine environment. Pregnancy per service would be reduced by 10% at a THI level of 80 compared to 70 (Mellado et al., 2013).
When accounting for mortality, production and reproduction performances losses, heat stress would cost approximately $1 billion annually only to the North American dairy industry (St-Pierre et al., 2003).
How can Evonik’s solutions support the health and performances of cows under heat stress?
Mepron® as a solution to leverage energy metabolism, inflammatory status and oxidative stress The direct negative effect of higher environmental temperature on the appetite would explain only 35% of the reduced performances, the rest being attributed to a reduction in energy metabolism (Rhoads et al. 2009). When transition cows were fed Mepron®, the most efficient rumen-protected methionine source for ruminants, several enzymes involved in hepatic gluconeogenesis (Krebs cycle) were stimulated, supporting the energy production of dairy cows (Vailati-Riboni et al., 2019).
Heat stress promotes inflammation and oxidative stress in dairy cows. Supplementation with Mepron® alleviated inflammation and oxidative stress and improved neutrophil function during the periparturient and early lactation periods in Holstein dairy cows (Batistel et al., 2018). Modified concentration in several acute phase proteins indicated a reduced inflammation status with Mepron® supplementation. Moreover, higher concentrations in antioxidants such as glutathione and lower concentrations in reactive oxygen species clearly demonstrated the beneficial effect of Mepron® on oxidative stress.
The dual purpose of K-pron®: additional potassium and rumen buffering effect Increasing the dietary electrolyte balance (DCAD) to 450 mEq/kg DM can be beneficial for ruminants exposed to high temperatures (INRA, 2019). Supplementation with the potassium carbonate source K-pron® can help reaching this target. Potassium supplementation to dairy cows in hot conditions increased milk yield by 3 to 15%.
The additional potassium compensates the mineral loss in sweat and ensures proper biological functions of essential cells. Indeed, water evaporation by sweating can double between a lactating cow kept at 18°C or above 30°C, inducing severe losses of essential electrolytes such as potassium (Khelil-Arfa et al., 2014).
As the cow experiences hot temperature, her natural activity will reduce, including feed intake which further leads to lower rumination and rumen pH. But not only this factor contributes to the apparition of rumen acidosis during heat stress (Bernabucci et al., 2010): increased respiration rate (Lamp et al., 2015) and lower absorption of volatile fatty acids from the rumen also maintain low rumen pH and metabolic acidosis. Carbonate sources such as K-pron can prevent the apparition of rumen acidosis and improve rumen health.
For more information, see:
animal-nutrition.evonik.com/en/species/ruminants
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