HEAT STRESS DURING DRY
PERIOD AFFECTS CALVES

Cows that experience heat stress during their dry period produce less milk, are more prone to disease, and are more difficult to breed back than cows that do not suffer from heat stress just prior to calving.  These negative impacts of heat stress on cows are well known.  But what about the calves these cows are carrying?

In the April 2013 issue of Penn State's Dairy Digest, Coleen Jones, research associate, discusses a recent study conducted at the University of Florida that offers some new insight in calves born to cows that experienced heat stress during the dry period.  The study was published in the December 2012 issue of the Journal of Dairy Science.

Some important findings include:

*  Calves born to heat-stressed dams weighed 13 pounds less at birth and 28 pounds less at weaning than calves born to dams with access to cooling.

*  Colostrum lgG content was not affected by heat stress.  However, calves born to heat-stressed dams were less efficient in absorbing lgG from colostrum and had lower serum lgG concentrations for the first 28 days of life than calves born to cooled cows.

*  Calves exposed to heat stress before birth also had a compromised T-cell response, as measured by the number of monocytes in circulation at 7, 28, 42, and 56 days of age.

These results confirm that calf body weight can be significantly impacted by heat stress during the final weeks of gestation.  In addition, both passive transfer and cell-mediated immunity were compromised in calves exposed to heat stress.

Wtih summer just around the corner, now is the time to evaluate our cooling strategies.  Don't forget about your dry cows!

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DAIRY INDUSTRY BRIEFS (DIBS)

Plummeting prices in the dairy industry are creating critical cash-flow and long-term survivability issues on Ohio's 3,328 dairy farms.  Cost-cutting decisions must be made with full awareness of both short and long-term production and economic consequences.

OSU Extension's Dairy Working Group, a collaboration of OSU Extension and OARDC faculty is identifying and addressing critical issues in five areas:

• Nutrition and feed costs
• Reproduction and health
• Calf and heifer management
• Business issues
• People and stress management

New DIBS (Dairy Industry BriefS) have been posted at http://dairy.osu.edu/DIBS/dibs.html and will continue to be posted regularly.  Please check this web site for up-to-date news and information.