Ol’ Man Winter is a Thief!

– Jeff Lehmkuhler, PhD, PAS, Beef Extension Specialist, University of Kentucky

Last winter we had a dramatic increase in the number of cattle deaths compared to previous winters. Excessive rain contributed to these losses and led to wet haircoats and mud conditions in the fields. In the midst of last year’s muddy conditions, we did a series of meetings discussing the effects of rain and mud. I discussed the impacts of wet haircoats on lower critical temperatures and increases in energy for maintenance. When I looked back over a 110-day period that spanned November into February, the local Mesonet station had recorded precipitation 50 of those days. I think Ol’ Man Winter has stolen our winter weather and your profits heading for warmer weather to relax.

How big of an impact is this weather on cattle? Not much research has been conducted under the exact conditions many of you may be dealing with on your farms. We have to interpret the research that is available and make educated guesses on how much the energy needs of cattle increases due to these conditions. This said, you should plan on greater energy needs of cattle outside and closely monitor cattle body condition and health.

I like to show the old foot in the box research in meetings. Ag engineers published work in the 1970’s looking at the impact of mud depth and moisture on the energy needed to lift a leg. These researches obtained a cattle leg from an abattoir and fixed an eye screw to the top of the leg bone. The foot was placed into a box and surrounded by mud of varying depths and moistures. At 1” of mud depth, about five pounds of force was necessary to lift the leg. As depth increased, force required to lift the leg out of the mud increased. The force needed to lift a leg from 8” of mud ranged from approximately 25 pounds to over 105 pounds. That is a 5 to 20-fold increase in the energy needed to lift a leg to take a step. In another paper, researchers reported that during the winter when forages in pastures were limited, cattle activity from traveling or walking accounted for about 20% of the daily energy expended. Collectively this would mean that walking through mud could potentially increase energy needs 100-400%. I don’t feel mud alone will increase energy needs 4-fold as cattle simply won’t walk as much through mud reducing activity. However, this research illustrates why you find it so hard to pull that boot up out of the mud.

The equation 0.077 *(shrunk body weight, kg)0.75 is assumed for cattle to determine the megacalories (mcal) of energy required for maintenance per kilogram of live body weight under thermoneutral conditons. A 1,200-pound animal would require approximately 8.4 mcal of maintenance energy daily. Feedlot researchers in Colorado followed cattle after severe weather conditions experienced during the winter of 2006-2007. The monitored live weights and feed intakes over this period of severe weather. Cattle performance was negatively impacted by extreme winter weather. They determined the net energy for maintenance equation that explained the observed cattle performance was 0.1919 mcal * (shrunk body weight, kg)0.75 or 21 mcal/d. These cattle had a 2.5-fold increase in maintenance energy needs for that period of extreme winter weather conditions in Colorado.

We may not know exactly the impact of the environmental conditions on cattle maintenance requirements, but it is safe to say that energy requirements are increased. Providing 3-4 pounds of a commodity feed would increase the energy intake of a beef cow by approximately 20%. This can help offset the increased maintenance needs during periods of time such as the past 3-4 days when it has rained constantly with daytime temperatures in the mid-30’s to low 40’s.

Providing cattle the nutrients they require to maintain body condition will provide benefits in the long run whether through enhanced cow immunity, calf vigor at birth, greater passive immunity to the calf or greater conception rates early during the breeding season. I would encourage you to test your hay and work with your local county extension office or nutritionist to develop a winter feeding program. Best of luck keeping your boots out of the mud and tell Ol’ Man Winter to bring us some colder, drier weather.