Summer will soon be upon us, bringing with it intense heat and humidity. This heat and humidity is particularly stressful for the lactating dairy cow because of her high production potential, adding to the heat load she must dissipate during hot weather. Because of heat stress, the lactating cow suffers reduced feed intake and milk yield, resulting in lower profitability. Heat stress is a factor for five to six months of each year, so by reducing its effects there is potential for significant gains in productivity over a substantial period of time. One needs to prepare for hot weather before it arrives. Modifying the environment of the cow to minimize the effects of heat stress will help the cow adapt to weather changes, and will help minimize the sharp drop in production we often see when hot weather starts.

Following is a list of practices one can implement which can help alleviate the effects of hot, humid weather.

ENVIRONMENT

Provide shade for cows at all times to reduce the effect of radiant energy from sunlight. This includes loafing areas, holding pens, feeding areas and water troughs.

Sprinklers to wet the cows and fans to speed evaporation provide substantial cooling for the cow and increase feed intake. Cooling at the feed area and in the holding pen is beneficial. If cows are wet in the holding pen, make sure they are dry before milking.

To minimize potential for mastitis, do not let cows have access to muddy areas or stag- nant water. Fill the areas, concrete them, or fence them off.

Do not crowd cows into holding pens or force them to crowd under limited shade. This only adds to the heat stress.

Total mixed rations minimize selection by the cow and minimize reductions in forage intake which may occur in hot weather.

Balance rations to account for reduced intake during hot weather. This means increasing the concentration of nutrients such as protein and energy.

Balance minerals for hot weather feeding. Research shows greater milk yield with potassium above current recommendations. Have potassium at 1.2-1.5%, sodium at .3-.4% and magnesium at .3-.35% of the diet dry matter.

Deficiencies or excesses of certain nutrients make the cow less efficient. Make sure the ration is balanced for all nutrients.

Consider reducing the fiber content of the diet. Be careful, because too little fiber causes digestive problems and lowers fat test. Go no lower than 18-19% acid detergent fiber.

Use very high quality forages. High quality forages are more palatable and will help maintain intake during hot weather.

Consider a dietary buffer such as sodium bicarbonate. Buffers help to maintain intake as well as fat test, especially in low fiber diets.

Add fat to the diet. Fat has a high energy density and will help maintain energy intake during reduced feed intake. Whole cottonseed, soybeans and commercial fat products are options.

MANAGEMENT

Feed cows during the cooler hours of the day when cows are more comfortable and likely to consume more feed.

Feed cows frequently to stimulate intake and minimize heat load from digestion of a large meal.

Clean water troughs frequently and provide unlimited fresh water. It may pay to keep cool well water cool using insulated waterers or by shading the trough.

Minimize social stress by minimal regrouping.

Move cows during cooler evening hours and avoid moving cows long distances, especially during the hottest part of the day.

Remember to protect your dry cows too. Research shows that simply shading dry cows during the summer increased production during the following lactation.

Consider these practices to encourage greater feed intake and milk production during the hot, humid summer months. It is important to be ready for hot weather before it arrives, because it is difficult to regain milk production after it has been lost to heat stress. Management to reduce the effects of heat stress will minimize "summer slump" and improve profitability.