Use this checklist as a starting point to minimize the effects of heat stress and improve your day-to-day management.
Review Feeding Strategies and Timing. Consider feeding protocols that accommodate cows during hot weather. For example, slowly shift feeding schedules so that fresh feed is offered very early in the morning and/or very late in the evening to encourage feed intake. Depending on cooling in the holding pen, milking may be moved to occur during the coolest parts of the day as well.
Increase frequency of bunk push-out/clean out, particularly if feed line soakers add moisture to existing feed in bunks.
Rework your Ration. Visit with your nutritionist to evaluate rations. For example, potassium is in high concentrations in sweat and as temperatures rise, cows lose a significant amount through sweating, panting and urination. Increase potassium to 1.8 to 2% of the total ration dry matter to buffer the rumen and raise DCAD levels to +35 to +45 when cows need it most. Use the safest and most consistent source of potassium during hot weather by including DCAD Plus® Stabilized Potassium Carbonate in your ration.
Dietary sodium can be raised to a maximum of 0.8% of total ration DM to adjust DCAD as needed. Also, depending on the severity of decline in dry matter intake (DMI), you may have to increase ration nutrient density to offset the decline.
Reducing fermentable energy in the ration by feeding rumen inert sources like MEGALAC® Rumen Bypass Fat as a partial substitute for starch can help minimize the effects of heat stress as well. Minimizing rumen degradable protein and maximizing rumen undegradable protein to account for reduced starch in the rumen can be beneficial, too.
Watch Stocking Rate and Feed Space. Cooling tools can only go so far if animals are overcrowded. It’s recommended not to exceed 100% stocking rate for close-up, fresh and high-producing cows. Furthermore, these cows should have at least 30 inches of feed space to ensure adequate DMI.
Mid- to late-lactation cows and far-off dry cows can withstand a little more overcrowding, but try not to exceed 110%.
Table 1 shows the effects of stocking rate on space per cow for area, feed and water in pens with two or three rows of freestalls.
Table 1. Effect of stocking rate on space per cow for area, feed and water in pens with 2 or 3 rows of freetstalls.
Don’t Skimp on Water. Cows need plenty of water as temperatures and humidity rise. To ensure adequate water availability, barn waterers should provide 3.6 inches of drinking space per cow. It’s also highly recommended that cows have access to water troughs at milking parlor exits.
Offer Shade. All groups of cows must have access to shade, and it is especially important over holding areas. In dry lots, allow 45 square-feet of shaded area per cow. The ideal orientation for shade structures is north/south.
Properly Ventilate Facilities. All facilities, even those that feature natural ventilation, can benefit from fans when the weather gets hot. The goal is to keep air moving as much as possible. Cooling systems should be set to kick in at 68º F. to keep cows’ internal temperatures low.
Keep in mind that not all fans are created equal. The University of Illinois provides independent testing and performance ratings.
Make Sure Soakers Actually Cool Cows. The purpose of these systems is to soak the cow to her skin and, in conjunction with fans, allow for evaporative cooling. Soaking a cow that is already wet provides little additional cooling. Likewise, inadequately soaking a cow can create an insulating effect and unintentionally increase heat stress. Therefore, the more wet/dry cycles per hour, the more cooling can be achieved. The optimal wetting frequency will change based on the temperature humidity index, the type of soaker nozzle and water pipe diameter.
Don’t Forget to Cool the Parlor. Since cows spend a good part of their day in the holding area and milking parlor, don’t neglect heat stress abatement in these two critical areas. Fans in these facilities also need to be properly spaced and maintained for maximum effectiveness. Check your system to make sure it’s activated at the proper temperatures, and increase soaking systems frequency (if you have them) similar to those over feed bunks.