And I'm talking about research. Doesn't make any difference to me.
Here is the first research I found when doing a google search:
http://beef.unl.edu/impacts-of-cold-weather-on-calf-weights
The relationship also exists in cattle, according to a UNL study in the 1990's (Climate Affects Calf Birth Weights and Calving Difficulty,1999 Nebraska Beef Report, PDF 355KB). Researchers are still not clear why spring calving cows in colder winters have larger calf weights, but the study shows that for every 1 degree F decrease in average winter temperature, there is an increase in calf birth weights by 1 pound.
The UNL beef researchers studied the effect of colder than normal temperatures on calf birth weights. The six-year study found the coldest winter (11 degrees colder than the warmest winter) resulted in calf birth weights 11 pounds heavier when compared to the warmest winter. The exception was the winter of 1995-1996 when above normal average temperatures resulted in numerically (not statistically) heavier calf birth weights. One possible reason could be the colder than normal temperatures in January when the cows were in their last trimester (the cows calved in mid-February to April 1st).
AND ANOTHER:
http://www.iowafarmertoday.com/news/regional/cold-winters-bring-heavier-calves/article_8dd4c2c1-6fba-51d5-9788-ee62d71e82d7.html
As cold weather moves into the region, cattle producers may want to pay close attention to how far the temperature drops.
The severity of winter weather could cause calving problems come spring.
For years, Glenn Selk, Oklahoma State University (OSU) Extension cattle specialist, heard talk of large calves born after a harsh winter causing problems for cows and heifers.
Both heifer and calf genetics were the same each year and fed similarly before calving.
"Some ranchers and veterinarians alike believe that calves born after a very long, cold winter have larger calves than those born after warmer weather," he says.
Researchers from OSU and the University of Nebraska looked at the effect temperature during winter has on calf birth weights and difficulties in spring-born calves.
The University of Nebraska collected data on 400, 2-year-old heifers at its North Platte location over three years.
While calving difficulty can occur in heifers due to genetics and nutrition, researchers found that climate adds to the problem.
When a bred animal is exposed to cold temperatures, blood is concentrated internally to maintain its core body temperature.
Researchers found during prolonged periods of cold weather, the fetus might receive more nutrition because more blood flows to the uterus.
Selk explains, "During hot weather blood is shunted away from internal organs toward outer extremities to dissipate heat, while the opposite is the case in very cold weather with blood flow directed toward internal organs in an effort to conserve heat and maintain body temperature."
The result, he says, is the change in maternal blood flow may affect fetal growth in a small way, but "result in a measurable difference."
Other research from the University of Georgia attribute the increase in fetal weight during winter to increased feed intake from supplemental feeding by the cow.
Whether it is redirection of blood or supplemental feeding, or a little of both, researchers found calf weights did increase after a cold winter.
The Nebraska research shows calves averaged 11 lbs. heavier with a 22 percent increase in calving difficulty when temperatures and wind chills were 10 to 11 degrees colder.
To help cattle producers estimate potential problems associated to weather, the researchers concluded calf birth weights will increase one pound, and calving difficulty will increase by 2.6 percentage points for each 1 degree reduction in average temperature