Dairy cows can’t take the heat

Source: Donna Amaral-Phillips, extension dairy specialist

The heat of summer is here and livestock are definitely feeling the effects. The following article from UK specialist Donna Amaral-Phillips provides some good information for dairy producers to help lessen the effects of high heat and humidity on the dairy herd.

Heat stress is hard on livestock and especially dairy cows. Dairy cows will first start to experience heat stress when the temperature-humidity index (THI) exceeds 68. You may notice them breathing heavily and panting in the early stages.

Cows are much less heat tolerant than humans. Lessening heat stress is extremely important to any dairy business, because heat stress decreases cow comfort and health, and most importantly decreases reproductive performance and milk production.

Some research indicates that the detrimental effects of heat stress on reproduction may start at a temperature-humidity index of 55 to 60. The THI is a combination of temperature and humidity that measures the degree of discomfort cows experience.

Some key points dairy farmers should consider regarding lessening heat stress include:

• Fans: Are your fans installed and maintained properly for maximum air movement and when temperatures are at or above 72 degrees Fahrenheit?

A temperature-humidity index of 68 is equivalent to a temperature of 72 degrees with 45 percent relative humidity. You should run your fan cooling systems continuously once the THI exceeds 68, especially covering the feed bunk, holding areas and resting areas. You should have enough fans to guarantee that there are no areas in the barn where air is not continuously flowing.

A general rule of thumb is to space box-type fans no more than 10 times the diameter of the blades at a 20-degree angle downward towards the bottom of the next fan. For example, if the blade diameter is three inches, your fans should be no more than 30 inches apart.

Fans spaced more than 10 times their diameter lose effective velocity and, as a result, cows will not be adequately cooled. Fan blades and housings should be cleaned at least yearly for improved performance.

• Sprinklers: Do you use a sprinkler system for your herd at the feed bunk and the holding pen?

You should have low-pressure sprinklers that wet the cows’ hair coat in areas like the holding pen and feed bunk, where the floor can become wet without consequence. Your sprinklers should come on for one to three minutes every 10 to 15 minutes to coat the cows hair and skin. Fans run continuously to allow for evaporation of the water.

• Barn Ventilation: Does your housing facility provide adequate natural ventilation and contain properly designed ridge openings or caps in the roof?

Ridge openings and open sidewalls allow for air removal from the barn. A ridge opening should be three inches wide for every 10 feet of building width. Ridge caps generally are not recommended, but if you use them, they should be at a height equal to 0.75 times the ridge opening.

Overshot roofs should allow three inches for every 10 feet of building width. These roofs are less desirable because they assume that air always blows in the same direction.

In addition, the roof slope should be 4/12, four inches of rise for every 12 inches of run. You should orient new facilities with the long axis of the barn placed east-west to minimize sun exposure inside the building during the summer months.

• Rations and Water: Do you need to make ration and water modifications?,Cows under heat stress will eat less often and consume less dry matter. To get cows to eat more, you should feed during cooler parts of the day, such as morning and evening.

Mix feed twice daily to prevent or minimize heating of the feed. During heat stress, water intake increases tremendously.

Make sure that your watering containers provide enough water for your herd and are cleaned daily. Watering containers should be placed throughout the barn so all cows can reach them.

In summary, we realize that the dairy business is one that requires a lot of attention to detail. If you put effort into minimizing heat stress, it will lead to improved herd health and increased milk production. To get the pay off, you must follow these key principles and put them into practice on your farm.

For more information on dairy heat stress and other agriculture, food and environment topics, contact the Clinton County Cooperative Extension Service.

Educational programs of the Cooperative Extension Service serve all people regardless of race, color, sex, religion, disability or national origin.

Upcoming Meetings:

Grain producers meeting at

Wayne County Extension Office

Area grain producers are invited to a meeting at the Wayne County Extension Office located at 255 Rolling Hills Blvd. in Monticello, Kentucky on Thursday July 24th at 1:30 p.m. CST. Representatives from Tyson Foods purchasing department will be at the meeting to discuss purchasing grain for the new feed mill located here in Albany.

Grain storage meeting at

Clinton County Extension Office

A grain storage meeting will be held via Microsoft Lync at the Clinton County Extension Office on Tuesday July 29th at 8:30 a.m., as part of a grain series program conducted by the UK Extension Service.

Sam McNeil will present information on factors that should be considered when storing grain. All area grain producers are invited to attend. For more information please contact the Clinton County Extension Office at 606-387-5404.