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Tough Weather Conditions Continue for Cows in the South

March 3, 2014

The winter seems relentless with another blast of cold area dipping into the south in early March. Now is the time cattle producers are looking for 50F+ daytime temperatures with just enough rainfall for cool-season grasses to kickoff spring growth. This latest system brought much needed moisture into the state; yet, the cold is continuing to put pressure on hay based diets to meet the nutritional demands of cow herds that have started calving.

The graph below, representing the northern one-half of Arkansas, shows how often the wind chill temperature fell below beef cow lower critical temperature (LCT) since December 1, 2013. For the most part, the winter period has been dry across Arkansas. Just over 80% of the days have been dry. While ranchers need soil moisture to improve, the lack of winter precipitation has been beneficial to cow comfort. As noted in a blog in early December, cows with a winter hair coat are within their ‘comfort zone’ at temperatures as low as 32F. This comfort zone is even lower for cows with a heavy winter coat. However, very cold temperature has made its way into the deep south on several occasions, creating cold stress for cow herds, despite having a dry hair coat. While conditions vary across the state, analysis of weather data from a reporting station in northern Arkansas showed 3 periods (9 to 15 days in length) of conditions 15F below LCT. Nearly one-half the month of February across the state was below cow LCT, a period when cow nutritional needs are increasing as calving approaches or begins. As a reminder, cow energy needs increase 1% for each degree below LCT. Cows on marginal quality hay diets with little to no supplemental feed are showing the impact of this cold stress through loss of body fat (condition score).

cow lower critical temp arkansas witner 2013-14

With calving season underway for many herds and breeding season to begin in a few months, here are a few management considerations.

  • Separate cows into feeding groups according to body condition. Cows that are excessively thin, especially young females, may not recover in time for spring breeding; therefore, the financial aspect of feed management for extremely thin females must be considered.
  • Ramp up supplemental feeding programs as cows begin calving. This is particularly important for herds without spring pasture.
  • Producers using tubs and liquid feeds for supplements will need to provide supplemental grain/byproduct high energy feeds as lick feeds don’t supply enough supplemental energy for lactating cows or for periods of cold stress.
  • Do not allow cows to graze spring pasture until there is sufficient forage accumulation to support heavy grazing activity. If hay supplies are limited, substitution of grain for hay may be necessary until pasture forage becomes readily available.
  • Feed magnesium to cows that will be calving during March on cool-season grass pastures.
  • Regularly evaluate cow body condition from now through breeding. As breeding season approaches, evaluate the feasibility of ramping up feeding of moderately thin cows and the feasibility of short-term (48h) calf removal. These practices do not guarantee significant improvements in breed-up but may be worth trying as labor and finances permit.
  • Use early pregnancy detection methods (ultrasound, blood test) to determine further management of cows that did not breed back.

As a final reminder, body condition at calving is critical to calving interval or overall pregnancy rate for a short breeding season. Winter weather in Arkansas is inconsistent; so, be vigilant at paying regular attention to cow condition and 5 to 7 day forecasts. Loss in body condition this winter may have partially been avoided or rate of condition loss slowed by good nutritional management (feeding gestating beef cows high quality hay or moderate quality hay with 3 to 5 lbs grain during cold stress). Most of the temperature departures that created cold stress was associated with cold air, not cold air plus a wet hair coat. In addition, 60% of winter days had substantial windchill (> 5 MPH wind) with an average daily temperature of 40F during those days; therefore, access to wind barriers could had made a difference as well.

Prepared by: Shane Gadberry, Associate Professor

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