Keeping cattle cool and comfortable is important for maintaining weight gain, milk production and reproductive performance. The temperatures that cattle prefer, 40 and 65oF, are cooler than what humans prefer, which means cattle display signs of heat stress even in what we would call “cool” temperatures. Signs of severe heat stress can range from slobbering, high respiratory rate (panting), open mouth breathing, lack of coordination, and trembling. Dairy cows can exhibit decreases in milk production due to heat stress at temperatures as low as 72o F and 45% humidity while beef cattle can begin to show signs of heat stress at 77o F. In Kentucky, beef cattle can display signs of heat stress in early spring while dairy cows may show signs much earlier. Cattle need a period of time to acclimate to the ambient temperature.

Heat stress has many negative effects on cattle which result in significantly decreased animal performance. Heat stress affects the reproductive performance of females and males. It takes six weeks after removing the effects of excessive heat for the animal to recover reproductively. Cows often show decreased conception rates, decreased duration and intensity of estrus, decreased calf birth weight, and increased early embryo mortality when experiencing heat stress. Milk production and weight gains are also considerably decreased. Heat stressed cattle spend less time grazing resulting in less feed consumed which partially explains the observed reduction in performance. Any and all operations can be negatively impacted by heat stress. It is important to look ahead in early spring and prepare to reduce heat stress for the grazing season.

Cattle should not be worked during times of extreme heat, and during the summer months they should only be worked during early morning while it is cooler. Even when temperatures cool off in the evening, it is not a good idea to work cattle because their core body temperature peaks two hours after the high for the day and it takes cattle at least six hours to dissipate the heat load gained. For instance, if the peak ambient temperature is reached at 4:00 pm, cattle will not have dissipated their heat load until midnight or later. Cattle worked in the early evening will have a greater chance to overheat.

Cattle grazing endophyte-infected tall fescue can experience more intense heat stress than cattle grazing other forages. Blood flow to peripheral tissues or skin is reduced which diminishes the animal’s ability to dissipate body heat. A rough hair coat and failure to shed winter coats are common symptoms of fescue toxicity. Body temperature and subsequently respiration rates are increased, increasing maintenance energy needs. Taking steps to reduce fescue toxicity, such as removing livestock from endophyte-infected fescue fields during periods of extreme heat, can also help reduce the severity of heat stress in the herd.

Dairy producers often have fans in their barns and holding pens that circulate air and help keep cattle cooler. These fans can be put on a thermostatic switch where they are activated at a certain temperature, and several producers have already seen those fans come on this year. These fans accompanied with sprinkler systems are effective ways in helping keep cattle comfortable while being confined in a barn. These sprinkler systems are designed to wet the cattle’s hair coat completely within 2 minutes and remain off for the remaining 12 to 15 minutes of the sprinkler cycle and fans run continuously to help evaporate the water from the cow’s hair coat. A “mist”-type system is not recommended in Kentucky because with our humidity the mist creates a steam bath effect which increases heat stress.

Allowing cattle access to shade, and cool water at all times is vital to reduce heat stress. Trees are a valuable source of shade that is inexpensive to producers. Cattle need a minimum of 20 to 40 square feet of shade per animal to be comfortable. The height of artificial shade structures should be at least eight feet tall to allow sufficient air movement under the shade. Another option is to turn cattle out to pastures without shade at night, and allow access to pasture fields with shade during the day. Reducing heat stress in the herd will increase animal performance and overall profitability. For more information on fan and sprinkler systems see http://www2.ca.uky.edu/agc/pubs/aen/aen75/aen75.pdf

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MASTER GRAZER an educational program to improve grazing practices in beef, dairy, goat and sheep herds

There is no debating that this spring has shown the stranger side of Kentucky weather. The cool weather just refused to go away, surprising us with multiple April snow days. But hopefully we can put all that in the rearview mirror and focus on the work at hand now that the weather has improved.

As I’m sure is the case with most everyone else, we got our fertilizer spread late this year. The first cutting hay crop looks to be short and thin compared to normal, but hopefully we continue to get some moisture throughout the summer and the second cutting can make up for it.

Calving season went well again this year despite all the mud in February and March. We ended up with an AI conception rate of 66% for the first calf heifers, and 60% for the cows. We also had 68% of the calf crop on the ground in the first 30 days of the calving season. The main calving season lasted 50 days, not counting the handful of stragglers that always have to drag it out. Despite the muddy conditions, this years calving was a success.

Due to the muddy conditions we had to divide the cows up into more groups than we normally do to be able to spread the mud out and not tear up each feeding location quite as much. This meant that there was a lot more manure to clean up than usual. Last year we hauled around 40 loads of manure onto hay fields, and this year I would estimate that we have close to double that amount that needs spread. We also worked on repairing a lot of damaged areas that needed reseeded. We lightly disced the areas and then drilled in rye grass to try to get some quick cover on them. With the cooler weather they have not germinated as quickly as I would have liked but I am still hopeful.
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As spring time get kicked into full gear I hope that you find enough time to get everything accomplished. It is a challenging time with so many task demanding your attention, but if it means winter is over, then I am up for the challenge.