The first calves of the season hit the ground Sunday on the EJE Ranch.
We haven’t had February calves for a long time. When I was a lad we calved in January and February. That was the common practice at the time. We raised cattle and grew crops, so it made sense to calve in late winter so you could be in the field in the spring.
Sometime after I joined the Navy we quit farming, planted crop fields back to grass, and went to an all-cattle operation. Since there was no longer any spring farming to do, it made sense to calve in April and May, when the weather was nicer. I’m guessing the last time we had February calves was about 1980.
Last fall when I was battling a bone infection and couldn’t do a proper job of animal husbandry we sold the cow herd. I got better in January and we bought a group of bred cows. They were due to begin calving March 1 and continue for 70 days.
Nature doesn’t care much about human math, though, and it’s far from uncommon to have early calves. So Sunday we had the first two. It was cold and clear and fairly calm, so pretty good calving conditions for February.
It’s far from uncommon to get questions about how cattle are able to survive outside in the cold of winter. A lot of folks assume that cattle need to live in the barn in winter, just as people need to live in houses. And there are places where cattle are housed during the winter. This is just not one of those places.
So, cattle and cold. Cattle are mammals, as are humans. Like humans, cattle are endothermic and homoeothermic – they regulate their body heat via internal metabolism and have to keep that level of body heat within a pretty narrow range to survive.
In mammals the autonomic nervous system is in charge of maintaining body heat, the process of which is called thermoregulation. To do this the ANS has clever sensors distributed everywhere in the body, measuring all kinds of parameters; temperature, blood pressure, heart rate, blood chemistry, and so on..
When the body begins to lose heat, the hypothalamus, which is in charge of the ANS, recognizes the situation by “reading” the bodies distributed sensors. It then coordinates a series of neural and hormonal commands, which cause the body to do things to compensate for heat loss and to generate more heat.
Neurologically, it causes goose bumps and shivering. Goose bumps don’t do much for people, but in most other mammals, who happen to have fur coats, goose bumps actually erect the hair to trap an insulating layer of warm air. Involuntary shivering generates muscle heat to help replace warmth lost to the cold.
At the same time hormonal commands cause enzyme cascades, which in turn ramp up cellular metabolism throughout the body. As the cells increase their activity they generate more heat. They also require more nutrients, so other hormonal/enzymatic cascades free up carbohydrates (sugars) and lipids (fats) to stoke the cellular fires.
If the body continues to cool, other neural signals cause blood vessels closest to the skin to constrict. This serves to keep warm blood away from the relatively colder surface of the body, thereby conserving warmth around the vital organs in the core of the body.
A well-nourished mammal can usually strike a balance between heat loss and heat manufacture and retention. Mammals are designed for this and they (we) do it all the time. We can survive and thrive in very cold temperatures.
There can be complications though.
If a human’s clothing gets soaked it loses much of its ability to insulate. The same is true of a mammal’s fur coat. Heat is lost that would otherwise be conserved. Add in some wind and prodigious quantities of heat will be wicked away. This can be a recipe for disaster.
Even when cold and wet though, so long as the body can generate heat a bit faster than it’s lost, all can be well in the end. Eventually body heat will dry clothing or fur, and things will return to a livable balance.
But for the body to generate heat, it must have enough stored energy to metabolize.
Mammals can survive remarkable extremes of cold. We humans usually don’t have to do this because we have ways of keeping our immediate environment warm; furnaces, car heaters, etc. But lacking these, so long as we’re properly nourished, clothed and sheltered from wind and wet we can easily survive extended exposure to sub-zero temperatures.
And that is, in a nutshell, how cattle survive the cold. My job as a rancher is to make sure they are nourished and have a way to shelter from extremes of wind and wet. In those situations where there is too much cold, wind and wet, and not enough nutrition, cattle will die. Fortunately, those situations are rare and cattle are incredibly tough and adapted to living in nature. It’s seldom a big problem.
Things are a little bit different when it comes to newborn mammals. I’m talking specifically about cattle, but there’s really not a lot of difference between newborns of any mammalian species. We’re accustomed to human babies being born in hospitals with incubators and fetal monitors and lots of staff rushing around, but there was a time, not so very long ago, when human babies were born at home with the mother often the one to coordinate assistance. And not long before that, home might have been a tent or a cave or a clearing in the forest. The fact that humans survived as a species in the absence of hospital delivery tells us that there is probably something innately survivable about unassisted parturition.
When mammals are born they experience a huge environmental and metabolic change. In the womb thermoregulation is taken care of by the mother’s body. Oxygen and nutrition are provided via the placenta and umbilicus. Many of the fetus’ organs are functioning, such as the heart and circulatory system and brain and nervous system. But many of the organs are dormant, such as the respiratory system and the digestive tract.
At birth the newborn has to begin regulating its own body heat, begin breathing, begin metabolizing stored energy, and begin to take in and digest food to fuel the process.
When a calf is born in the cold it has to do all of these things pretty quickly.
It’s born wet and begins to shed warmth immediately. The calf’s autonomic nervous system immediately kicks into high gear. Muscles under the skin erect still-wet hairs (goose bumps) and deeper muscles begin to shiver. Its diaphragm begins to expand and contract, air rushes in and out, oxygen and carbon dioxide begin to be exchanged.
It takes a lot of energy to do these things. The first dose of energy comes from carbohydrates -- blood sugar already present and circulating. But that’s a limited source. At the same time the calf’s cells are burning glucose, hormonal and enzymatic cascades begin the process of metabolizing adipose tissue. Some of this is white fat, and some is brown fat. In very simple terms, white fat becomes ATP (adenosine triphosphate, a form of chemical energy used by cells) while brown fat is metabolized rather directly into heat. Metabolizing fat is far more complex than that, but it’s a good first approximation.
Just as blood sugar is limited in the neonate, so is the quantity of available adipose tissue. So the newborn calf must very quickly struggle to its feet, totter to the udder, and begin to ingest colostrum. This is the first milk that the mother produces and it’s loaded with sugar, fat and immune factors.
Once the calf gets dried off and begins digesting and metabolizing a belly full of colostrum it’s in good shape. But it only has limited time and internal resources to accomplish this first, vital task.
If the calf doesn’t get up and nurse, it will die. And even if it does get up and nurse, if it loses heat faster than it can make heat, it will die.
Fortunately, there are things the rancher can do to help. Chief among these are to provide good nutrition for the gestating cow, arrange for appropriate calving shelter, and when needed, help the calf dry off, provide supplemental colostrum via a bottle or stomach tube, and provide an external source of heat to slow or halt the rate of heat loss.