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Summer Heat 2015


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How to avoid the summer slump?

Although we cannot change the weather, key is to manage the cows as best as you can which means catching cows, especially fresh cows, with high SCC counts as quickly as possible. Second, monitor production levels and discuss making ration changes, timing of feeding and increase access to water. Third make sure to catch cows that lost a pregnancy as quick as possible so you can breed these cows as quickly and minimize the loss in days open. And don't forget, milk samples can provide important diagnostic information too.

AgSource provides several tools that will help you manage through the summer months:

  1. Continue to test during the summer months
  2. Use the Udder Health Management Summary to catch new and fresh cow infections and address chronic infected cows.
  3. Additional milk based diagnostics such as PCR and Cultures that can help you and your veterinarian determine the appropriate treatment for your cows
  4. Use the AgSource Milk pregnancy test during the summer and fall month and identify cows that may originally have been confirmed pregnant however lost their pregnancies.
  5. Remember a milk sample can also be used to monitor Ketosis and Johne's problems associated with stress!

Click here to learn more about KetoMonitor.

Click here for more about Johne's Milk ELISA testing.

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Monitor, Manage and Improve

Management information from regular monthly DHI testing can help  -

o Monitor side effects of heat stress on udder health, production, and
o Keep losses from heat stress to a minimum
o Better evaluate your heat stress reduction strategies

How well are the new sun screens, misters and ventilation systems working to minimize cow stress and maximize cow comfort in extreme weather? Did the modified rations and feeding schedules benefit production?  AgSource products and DHI test day information provide a means to monitor production, udder health, and fresh cow management challenges during the summer heat, but only if test day intervals remain constant. 

Direct Impact on the Bottom Line

Managing udder health and reproduction has a direct impact on the bottom line. Research has shown that increases in SCC Linear Score can be associated with decreases in production and higher costs associated with treatment of cows.  For example an increase of one linear score on 1st lactation cows reduces lactation milk production by 275 lbs and 2nd and greater lactation cows by as much as 575 lbs. 

Increased days open has a negative impact on production as well. The losses associated with longer days open on 1st lactation cows is ~$2/day and for 2nd and greater lactation cows as much as ~$6/day. Below is an analysis of data obtained from all AgSource herds showing how the summers of 2012 and 2013 impacted several areas of herd management and steps you can take to manage the impact of the summer heat.

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Seasonal Impact on Production

Herd production levels measured as MLM dropped by as much as 6 lbs from 84 lbs in May 2012 to 78 lbs in July of 2012, SCC rose from 195,000 in January 2012 to 258,000 in August.  Similar observations took place in 2013 where MLM dropped by 6 lbs from a peak in May 2013 to a low in September 2013. SCC levels increased from a low of 215,000 observed in December 2012 to a high of 277,000 in July 2013.

Track herd production using the Herd Summary. To see an example report, click here.

Figure 1 shows the seasonal impact on SCC and Management Level Milk  (MLM is standardized milk production to a second lactation cow, 150 days in milk with 4.0% Fat and 3.3% Protein)

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Seasonal Impact on Udder Health

New cow infections generally increase by 3-4% while fresh cow infection rates increase by about 5-6%.  Although herd size has an impact on the overall value, the increases seen in infection rates and during the summer months impact herds of all sizes.

Keep a close eye on your fresh and transition cows with the Fresh Cow Summary report - Click here to see an example report.

Figure 2 shows the impact season has on New and Fresh Cow infection rates by month.

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Seasonal Impact on Reproduction

Not only does the summer heat play a role in production and udder health, AgSource data shows it has an impact on reproduction as well.  Figure 3 shows the impact seasonality has on days open and services per conception.  Data is shown based on when each cow calved.  Cows calving in the spring months and bred during the summer months show higher days open and higher services per conception rates compared to those cows that were bred during the cooler months.


Cows calving spring of 2011 versus fall of 2011 show a difference in 18 days open while cows calving in spring 2012 versus fall 2012 showed a 16 days open difference. Cows calving spring 2013 also saw an increased days open. To see an example of the Herd Summary, click here.

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What is heat stress? Signs and repercussions of heat stress       

Managing Heat Stress using DHI Records by Robert Fourdraine

Strategies to Improve Dairy Cows' Feed Intake during Heat Stress

The Value and Use of DHI Somatic Cell Counts National Mastitis Council

Economics of Heat Stress: Implications for Management

Milk Quality University of Wisconsin website - great resource!