Heat Stress During The Dry Period Has Lasting Negative Effects

Cows under a sprinkler.The negative effects that heat stress can have on a lactating herd are well known among dairy nutritionists and dairy producers, and heat abatement strategies for lactating cows are commonly employed on many farms in the Upper Midwest. But dry cows, a sometimes overlooked group, are also highly susceptible to heat stress. Importantly, the negative effects of heat stress during the dry period have a carryover effect into the next lactation that cannot be corrected by cooling the milking herd.

Several studies have examined the effects of heat stress on dry cows and cow  performance in the following lactation. On average, milk production is decreased 11 lb per day across the subsequent lactation for cows that experience heat stress during the dry period compared to cows that are not heat stressed during the dry period. Similar studies are summarized in the table below (adapted from Ferreira et al., 2016). Remember, all cows were cooled postpartum and the only difference is cooling or heat stress during the dry period.

In addition to lost milk production, cows that experience dry period heat stress have decreased fertility and decreased immunity through the subsequent lactation, as well as reduced birth weights and growth rates in calves from those cows. On average, calves born from heat stressed cows weighed 17 lb less at birth compared to calves born from dams that were cooled during the dry period. It is also important to note the lasting effects and delayed response of cows to heat stress. Each year the average lag time between the highest ambient temperature and the lowest milk production is consistently two months. Dairy cows experience heat stress when the Temperature Humidity Index (THI) rises above 68. The figure below illustrates the average THI for the Minneapolis area in recent years.

Respiratory Health and Safety

Dust exposure in the field agriculture is inevitable and most will encounter concentrations of dust during normal work. As a safety concern, dust concentrations from activities such as loading/unloading product or grinding/mixing grain, hay, or silage can affect health as exposure increases. Most people will have some reaction to dusty conditions. These reactions can range from a runny nose, chest tightness or wheezing, sore/irritated throat, nasal/eye irritation, or feeling of being congested to even bigger health problems such as “Farmer’s Lung” which can also develop. Exposure and health symptoms are complex, but you can take steps to keep safe & healthy. Simple actions such as staying in the cab with the door closed when unloading or using the wind to your advantage rather that standing directly in a cloud of dust any time grain is being moved or feed products are being mixed can be used to decrease your exposure to dust and benefit your health. Practicing these types of safe actions are important to keep in mind. For a full list of tips and information on maintaining respiratory health and safety in agriculture please visit: goo.gl/QSy7Tp.

It’s Winter in Wisconsin — Here Are Tips for Mitigating Cold Stress in Your Herd

  1. Provide an adequate quantity and quality of additional feed and clean, temperate water.
  2. Provide additional energy and electrolytes to ensure meeting the metabolic call for additional nutrients.
  3. Cow bedding and housing areas should be dry and free from manure with fresh bedding provided daily.
  4. Teed dips that include skin conditioners like glycerin and lanolin can help prevent frostbite and bacterial infections.
  5. Windbreaks in outside holding areas supply protection.

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