It can be a challenge to meet the nutrient requirements of dairy cattle during heat stress. This subject garnered a good share of attention during a symposium at the 2012 Joint Annual Meeting of the American Dairy Science Association, held July 15-19, in conjunction with four other animal science societies.
During the symposium, Greg Bethard, a dairy nutrition consultant based in Wytheville, Va., outlined goals that are important to keep in mind during heat stress:
1. Maintain rumen health, rather than try to cram extra energy into the diet.
2. Minimize pregnancy loss. Take a long-term perspective. The effects of heat stress are not limited to a two- or three-month window in the summertime. Think about how heat stress affects reproductive performance nine months down the road.
3. Keep cows as comfortable as possible. This is an obvious goal, but the importance of cow comfort and heat abatement can’t be stressed enough.
4. Minimize dry matter intake loss. Keep intakes consistent with good bunk management.
5. Minimize body condition score loss. Feeding fat is a strategy that can help with this.
6. Increase glucose precursors without breaking rule No. 1 above.
7. Minimize sorting. Sorting becomes a bigger issue during heat stress.
8. Don’t crowd close-up and fresh cows.
9. Minimize lock-up time.
10. Rethink the size of your transition facilities to accommodate changes in calving distribution that result from heat stress.
Drought conditions may cause some disruptions in water availability. For example, springs or surface water sources for grazing animals may cease to supply adequate water during drought conditions.
Emergency response plans should be developed to procure the water that animals need, points out Maurice Eastridge, professor and extension dairy specialist at The Ohio State University.
The approximate total water needs for the farm should be assessed, assuming the following: heifers 1 gallon per day per 75 pounds of body weight; dry cows 12 to 16 gallons per day; lactating cows, 8 to 10 gallons per day, plus 0.35 gallons per pound of milk.
Water deprivation severely limits animal performance and can be life-threatening in a short period of time, Eastridge says. Once water deprivation has occurred for an extended period of time, animals should NOT be given immediate free choice to the water. Overconsumption of water at this point can cause severe health issues. At first, animal exposure to the water should be limited, followed later with free-choice water.