Heat Stress in Cattle
1. Defining Heat Stress and its Implications:
The severity of heat stress is correlated to both the humidity level and the ambient temperature. The cow’s thermal comfort zone is approximately 12°C–25°C. Within this temperature range, the animal comfort is optimal, with a body temperature between 38°C and 39°C (Lefebvre & Plamondon, 2003). Above 20°C the cow suffers from heat stress: its health status and general performance are affected.
2. The Financial Impact of Heat Stress:
3. A Disrupted Energy Balance:
4. Acidosis Risks:
Strategies to Alleviate Heat Stress in Cattle
Water - Forgotten Nutrient
Ration Formulation for Heat Stress in Cattle
Fiber Level in Ration
Protein Level in Ration
Dietary Cation Anion Difference
Dietary cation anion difference (DCAD) is the difference between certain dietary minerals nominated as cations (Na, K) and anions (Cl, S) on the basis of charges they carry and is usually measured as milliequivalents of (Na+K) – (Cl+S) per kilogram of DM (Sarwar et al., 2007). Wildman et al. (2007) stated that keeping the DCAD at a healthy lactating level (200 to 300 mEq/kg DM) remains a good strategy during the warm summer months. Animal productivity is influenced more by the difference between these cations and anions than their individual effects when fed as a sole independent mineral source. In addition, Shahzad et al. (2007; 2008) reported that a diet having DCAD 330 mEq/kg DM has promoted feed consumption, water intake and resulted in greater milk yield and milk fat in early lactating cattle.<a< p=””> </a<>
- Provide high quality feeds like total mixed rations
- Increase the frequency of feedings
- Feed during cooler times of the day
- Keep feed fresh as much as possible
- Provide high-quality forage
- Provide adequate fibre
- Use of by–pass proteins can enhance the milk yield and protein content.
- Intake of sufficient cool water is probably the most important strategy for animals to undertake during heat stress.
- Use high-quality forages, and increase the energy density of the diet to reduce gut fill.
- Consider the addition of high-fat feeds, bypass fats or lower fiber feedstuffs.
- Alter feeding times to allow more feed intake at night, when it is cool.
- Utilize total mixed rations to reduce feed sorting by cattle.
- Ensure an adequate source of cool, fresh water. As temperatures rise into the mid-90s, dairy cows will increase their water intake by as much as 50 percent.
- Consider adding a nutritional supplement to help support normal immune function.