Watch for Short- and Long-term Effects of Drought on Cow Herds

BROOKINGS, S.D. -- The drought could affect the reproductive performance of cow herds this year and in the 2003 breeding season, a South Dakota State University specialist said.

Don Boggs, head of the SDSU Department of Animal and Range Sciences, said there are both short-term and long-term concerns producers should keep in mind.

Short term: "We have two factors that are really working against us as far as reproductive efficiency this year. One obviously is trying to breed cows in a time frame when the feed quality is going down. Normally we breed in the early to mid-summer, when the feed quality is increasing and availability is increasing. This year we have the opposite," Boggs said. "As those cows are coming into the breeding season, they're actually losing weight, or in what we'd call a negative energy balance. It's not a good way to get cows bred. We could be looking at lower reproductive performance."

Boggs added there is also the possibility that hot weather could affect bulls.

"If a bull goes sterile from getting too hot, you're looking at approximately 60 days or so before that bull will be fertile again. It really is an important consideration to watch and manage those bulls and make sure they don't get too warm during the summer," Boggs said. "If you suspect that you've had a problem and the bull might have gotten hot on you, you definitely need to get the bull checked and maybe get a replacement in there."
Both those factors could result in more open cows than usual, Boggs said. He said SDSU recommends that producers this fall do pregnancy testing on their herds early.

"Those cows that are open are certainly some to be identified as the ones to get moved out as soon as possible if you're trying to identify cows to sell. Open cows aren't going to be producing for a while, so it would be very important to identify them as early as possible and get them on a sell list."

Long term: Cows that have lost a lot of weight this summer call for special care to get them back into a moderate condition score before next year's calving season, Boggs said.

"If we have a cold winter, they're going to have a higher energy requirement due to being thin. Those cows need to have some body condition on them as they enter next year's calving season. Following calving, they're going to be losing weight from heavy lactation and again, not having those body energy reserves to pull on. We could see a carryover effect of the drought this year, even if we get recovery and have grass next year, from thin cows resulting in lower conception rates in 2003."

Boggs said early weaning can help, referring to a past research study in which cows under poor forage conditions lost two pounds for every pound gained by nursing calves.

"If your cows are getting thin at this point in time, early weaning those calves is the quickest way to get those cows back into shape. That calf nursing that cow really accentuates her requirements for both quantity and quality of feed." Early weaning lowers the cow's nutrient requirements, letting the cow have a chance to gain some weight and condition back prior to winter.

Contact: Don Boggs, (605) 688-5166

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Lance Nixon, Editor
AgBio Communications Unit
South Dakota State University
ACC, Box 2231, Rm 200
Brookings, SD 57007
Telephone: (605) 688-4653
Lance_Nixon@sdstate.edu