Chilly stress will increase a cow’s power requirement and might pull down her physique situation. Skinny cows may end up in weak calves being born within the spring and/or poor breed up. Winter storms have already swept throughout the Plains, giving indications this may very well be a protracted, chilly winter for cows already skinny on account of summer time drought stress.
The edge at which cattle have to begin utilizing power to keep up their physique temperature is known as the decrease essential temperature (LCT). Cows in good situation (BCS 5.0; 1-9 scale) which have a heavy winter coat that’s dry don’t want to make use of power to keep up physique temperature till the wind chill index is beneath 19°F. Offering wind safety can lower power wants by eradicating wind as an element. If cows have safety from wind, then the ambient temperature can be utilized to find out power wants. So, offering wind safety within the winter could be big for lowering supplementation wants on account of chilly within the winter.
To determine how way more power a cow wants, you’ll take the cow’s LCT minus the wind chill index (if no windbreak is offered) or ambient temperature (if wind break is offered) and that will let you know the % improve in power requirement. There’s a 1% improve in power wants for each 1° beneath the LCT. As an illustration, if ambient temperature is 21°F and wind velocity is 10, the wind chill index (WCI) is 11°F. For a BCS 5 cow with a dry winter coat with a LCT of 19°F, then 19 LCT- 11 WCI = 8% improve in power wants. You may search for the power wants of varied lessons of cattle right here. A 1200 lb dry cow in late gestation has an power requirement of 13 lb whole digestible vitamins (TDN) and the chilly described above elevated this want by an extra 8% which is the same as 1 lb of TDN for a complete of 14 lb/d.
Skinny Cows: A Snowball Impact
It is crucial that producers assess physique situation rating now, as many cows got here by means of the autumn skinny (< BCS 4) and winter has had an early begin in lots of areas. Physique situation is a danger administration technique and impacts the LCT. A skinny cow with a BCS 4 with a dry winter coat has a LCT of 27°F vs the 19°F of a cow in BCS 5. Thus, if the wind chill index was 19°F, a cow in BCS of 5 wouldn’t be utilizing any power to remain heat and a cow with a BCS 4 can be utilizing 8% extra power to remain heat. So, getting cows into good situation early within the winter could be helpful for managing danger of dangerous climate in that they’ve situation they will lose but additionally as a result of cows with greater BCS will lose much less with the identical quantity of power consumption than these with decrease physique situation. A 1200 lb gestating cow can solely eat about 31 lbs of medium high quality hay which is about 26 lbs DM. When you fed medium high quality hay (53% TDN on DM foundation) to a cow that was in a BCS of 4 when the windchill was 19°F, she wouldn’t be capable to eat sufficient hay to fulfill her power wants and can be dropping pounds whereas the BCS 5 can be gaining just a little situation. A sensible administration technique could also be to think about placing skinny cows in a bunch along with your first calf heifers as each have greater power requirement within the winter, which may enable for strategic feeding of upper high quality forage or supplementation when out grazing.
Moist Hair Coats End in Large Power Loss
Additionally it is vital to grasp {that a} moist hair coat forward of a snowstorm exacerbates the state of affairs. A moist coat will increase the LCT of a cow in good situation to 53°F. Thus, primarily anytime a cow’s coat is moist within the winter, they are going to be utilizing power to keep up physique temperature. Due to this fact, in winters with extra precipitation, particularly freezing rain, we frequently see larger decreases in BCS.
Assembly Cow’s Power Wants Throughout Chilly Stress
It’s not advisable to alter rations day by day however for prolonged chilly and/or moist durations take into account feeding extra of the identical ration, assuming cattle can eat extra of the everyday ration. If not, then offering a complement is a good suggestion. When feeding decrease high quality hay, dormant vary grazing or corn stalk grazing, extra feed might be wanted. One possibility is to alter to feeding the next high quality hay supply, if obtainable. Free alternative top quality hay (58 to 60% TDN) can work right down to temperatures of 34°F beneath the LCT of the cow (or -15°F for cows in good situation with dry hair or 19°F with moist hair). If cows are grazing, then supplementation with a excessive power feed could also be fascinating. Whereas corn can be utilized to offer extra power, it comes with danger. Feeding greater than 2 to three lbs/hd can lower forage digestion, particularly if the forage is decrease in protein. Feeding corn with some alfalfa on low protein forges can mitigate this subject. With 3 lbs of corn one might make up the distinction of about 15 levels F between the LCT of the cow and the wind chill index temperature, which for a cow in BCS of 5 with a dry coat, corn supplementation would cowl the elevated power requirement down to five°F or for a cow with a moist hair coat to solely about 38°F.
Distillers grains are another choice. Distillers is an efficient supply of power. It has extra power than corn, and since it’s excessive in protein, it doesn’t trigger as a lot of a substitution impact (won’t lower consumption of the forage a lot). Within the instance above the place the cow wanted an additional 1.2 lbs of TDN, feeding 1.2 lbs (as-fed) of dry distillers would supply the additional power wanted. Within the case of distillers and gestating cows, the kilos of TDN wanted to account for power used on account of chilly stress can be equal to the kilos of dry distillers that will have to be fed. Limitations on the quantity of distillers that may very well be fed can be extra primarily based on budgetary issues than digestive results.
When wind chill temperatures are extraordinarily chilly or the cow has a moist hair coat, a number of complement can be wanted to make up the larger power wants and preserve physique situation. As an illustration, if the wind chill was -10°F and the cows had a moist hair coat, then 8.9 lbs of dry distillers can be wanted to account for the elevated power requirement. Nonetheless, feeding these ranges is probably going impractical. A greater strategy can be to offer a smaller quantity of supplemental feed and to proceed to feed the additional feed after the climate has moderated to permit cows to regain power misplaced in the course of the storm.
Additionally it is vital to keep in mind that lactating cows have a a lot larger power requirement than pregnant cows. Given this, the mix of chilly stress and lactation can pull down BCS shortly. If lactating cows are additionally subjected to chilly stress, growing their power consumption previous to observing lack of situation is advisable.
Searching for extra data? Try the webinar Caring for Cattle in Chilly Climate.
