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Global Warming and Forage Preservation

Global Warming and Forage Preservation

Climate change affects cow and silage bugs

Climate changes represents a real challenge for tomorrow’s global livestock production. Global warming is impacting farming at various levels:


Heat stress is a growing issue for dairy cattle in many parts of the globe, particularly for high producing cows. A cow’s comfort zone is between 5-20°C. We are talking about heat stress when environmental conditions exceed this comfort zone. External temperature is not the only parameter to define heat stress since relative humidity is also important. Heat stress level is monitored thanks to the well-established Temperature Humidity Index (THI) scale. Heat stress results in reduced feed intake and milk production.  Experts estimate that it can cause 10-35% decrease in milk production. It also causes health issues such as rumen acidosis, impaired immunity and reproductive performance are impacted, representing an important financial burden to the industry.

Figure : THI scale to evaluate heat stress level in dairy cow. Yellow: heat stress threshold (milk loss begins) ; orange: mild to moderate heat stress; red: moderate to severe heat stress; purple: severe heat stress.


Drought and flooding episodes represent major stresses for crops, impacting their development, yield and nutritional qualities.


Silage is a constant battle between “good”, acidifying bacteria and “bad” spoilage bacteria or fungi. As the cows, bacteria have their own thermal comfort zone. Each species has what we call its own “thermal death point”.  Typically, desirable epiphytes bacteria such as lactic acid bacteria are generally killed above 45-50°C, while the bad guys resist to higher temperatures. Clostridia and bacilli are spore forming bacteria and resist to high temperature. A shift of temperature within the silo can impact the microbial ecosystems within the silos, resulting in different fermentation profiles.


Epiphyte bacteria species Thermal Death Point Bacteria species Thermal Death Point
(+) Lactobacillus buchneri1 <45°C (-) Listeria monoctytog. 5 63°C
(+) Lactobacillus plantarum1 42°C (-) Brucella6 58°C
(+) Lactobacillus paraplantarum2 <43°C (-) Pseudomonas7 60+°C
(+) Pediococcus acidiactici1 65+°C (-) Fusarium8 60+°C
(+) Pediococcus pentosaceus1 <60°C (-) Aspergillus9 60+°C
(+) Enterococcus faecium3 50°C (-) Candida10 60+°C
(+) Lactococcus spp4 <45°C (-) Klebsielleae11 60+C
(+) Lactobacillus brevis1 <43°C (-) Salmonelleae12, 13 55-65°C
(+) Leuconostoc spp1


<55°C (-) Shigella spp12 50-65°C

(Table compiled from:  1) Bergey’s Manual of Determinative Bacteriology; 2) Milic, 2004; 3) Martinez, 2003; 4) Lahtinen, 2012; 5) Rowan, 1998; 6) Jones and Martin, 2003; 7) Spinks, 2003; 8) Bollen, 1969; 9) Dornsch, 1993; 10) Dumalisile, 2005; 11) Wilbey, 2012; 12) Bandres, 1988; 13) Feechearn, 1983).