Whether the temperature will be subzero cold for the entire lambing and kidding season or only subzero for a portion of the season, it is important to ask how cold is too cold for newborn lambs and kids?
Research from Australia has shown that the greatest death loss in lambing occurs within the first 3 days of a lamb’s life. The issues we are worried about now are starvation and cold exposure.
Placental development begins d30 post conception (d30 gestation). Good placental development (remember all the nutrition the growing lambs receive comes through the placenta) is essential in producing healthy lambs that have good fat reserves at birth. Ewes that receive poor nutrition throughout gestation are more likely to have small, weak lambs that are lacking internal body fat.
Lambs are born with brown fat (an energy reserve) that helps them produce energy and heat post-birth. Eating frequently in the first few days of life is critical for lambs to maintain body heat. Hypothermia often occurs within the first 5 hours after birth. If the lamb has not been properly dried/licked off and has not nursed, it will have depleted its brown fat reserve within the first 5 hours of life. Colostrum is an important energy source (high fat) and good quality colostrum comes from well-fed ewes.
Why do lambs lose heat so fast?
The lower critical temperature for freshly shorn sheep is 50 degrees. Sheep with 2.5 inches of fleece have a LCT of 28 degrees. Goats are generally considered to have a LCT of 32 degrees. It is likely that sheep with a heavy fleece and goats with a heavy cashmere undercoat probably have lower critical temps than the above numbers, however, for the sake of this article we will go with what is listed.
Consider the changes experienced by a newborn lamb or goat kid: they are wet and were expelled from a warm environment to a cold one. If we think about a newborn lamb as a freshly shorn lamb and the lamb is born at 32 degrees, it is already 18 degrees below its critical temperature. In reality, the chances are it was born at a temperature much cooler than 32 degrees between the actual temp and any existing wind chill. These animals are in danger within minutes of being born, not hours.
Heat Loss occurs due to:
• Size – small lambs will chill faster than larger lambs, multiples will chill faster than singles, and lambs and kids have a large surface area to bodyweight ratio which allows them to lose heat quickly.
• Coat – the thickness of the coat matters, as well as the dryness of the coat. Also, goats seem to chill faster than lambs.
• Temperature – the cooler the temp is, the faster the lamb loses body heat.
There is no set amount of time a lamb or kid has before it will freeze to death in the cold winter. As mentioned above, quite a few factors play into the issue, including air temp, wind chill, whether the newborn has been dried off, multiple birth, goat kid vs lamb, and brown fat reserves. In all cases, the faster you can help newborns in distress, the better your chance of saving them.