What Is Cold to a Cow?11 February 2015
US - Cows in good condition will need their ration increasing in energy density by one per cent every degree Fahrenheit below the lower critical temperature, US beef producers have been told as a rule of thumb.
Lower critical temperature is influenced by both animal and environmental conditions, and, according to a Kansas State University Extension Agent, this includes hair coat and body condition.
Beef systems specialist Dr Justin Waggoner states in this months Beef Tips that the general rule of thumb for a cow in good body condition, (BCS = 5 or greater) is to increase the energy density of the ration by 1 per cent for each degree (Fahrenheit) below the lower critical temperature.
Cattle are most comfortable within the thermonuetral zone when temperatures are neither too warm nor too cold, writes Dr Waggoner.
During the winter months cattle experience cold stress anytime the effective ambient temperature, which takes into account wind chill, humidity, etc., drops below the lower critical temperature. The lower critical temperature is influenced by both environmental and animal factors including hair coat and tissue insulation (body condition).
The table below lists the estimated lower critical temperatures of cattle in good body condition with different hair coats.
In wet conditions cattle can begin experiencing cold stress at 59°F, which would be a relatively mild winter day. However, if cattle have time to develop a sufficient winter coat the estimated lower critical temperature under dry conditions is 18°F.
Cold stress increases maintenance energy requirements but does not impact protein, mineral or vitamin requirements.
The classic response to cold stress in confinement situations is an increase in voluntary intake. However, it has been documented that grazing beef cows may spend less time grazing as temperatures decline below freezing, which reduces forage intake (Adams et al., 1986) and makes the challenge of meeting the cow’s nutrient requirements even greater.
In many cases feeding a greater amount of low-quality hay may not provide sufficient energy. Therefore providing additional energy by feeding a relatively higher-quality hay or grain may be required.