For southwest Saskatchewan ranchers Barry and Anne Wasko, switching the heifer-breeding program a few years ago to select for shorter-gestation bulls is producing smaller but vigorous calves while reducing concerns about calving difficulty.
By breeding their Hereford/Red Angus-cross heifers to Black Angus bulls selected for EPDs showing shorter gestation, heifers are calving about 10 days sooner than breed averages and producing calves weighing about 70 pounds.
“They are smaller but they are very vigorous calves,” says Barry, who along with Anne operates Bar 4 Bar Ranches at Eastend, southwest of Swift Current. Aside from the main cow herd, they run about 160 head of bred heifers. “The calves are up and nursing in no time. It is important they get that colostrum into them within the first hour or so.”
Larger calves and those perhaps stressed during an assisted calving can be slower off the mark to get up, moving and nursing.
As Wasko made the transition to shorter-gestation bulls about five years ago, cases of calving difficulty (dystocia) have all but disappeared. “We still watch the heifers, but we don’t have to be out there every hour checking,” he says. “And it’s rare that any heifers need an assist.”
Selecting bulls for the shorter-gestation characteristic has been around almost as long as there have been EPDs and it is only one factor in selecting bulls for reduced calving difficulty. EPDs for gestation length, birth weight and pelvic area are among characteristics to be considered.
And there is quite a range in gestation periods between and among breeds. The average of all breeds is 283 days, while the Continental breeds such as Charolais, Simmental and Limousin, for example, average about 289 days. Among British breeds such as Angus, Shorthorn and Hereford, their gestation periods range from 281, 282 and 285 days respectively. And even within a breed, the gestation period can vary an additional 12 days on either side of the breed average.
But beef research shows that every day counts for calf size, particularly in late gestation. Studies have shown in the last 10 days of gestation, the fetus can grow from one to 1-1/2 pounds per day. So if gestation is five to seven days longer, that could potentially increase calf size by eight to 10 pounds.
Research also shows that heifers experiencing difficult or slow deliveries require more days of postpartum interval to cycle and rebreed. Studies show if a calf is born at 275 days gestation versus the breed average of 283 days, the female will usually have an easier delivery and have an additional eight-day postpartum interval advantage.
Still further research shows among first-calf British-breed heifers, an 80-pound birthweight calf appeared to be the tipping point. As birthweight increased more than 80 pounds, so did calving difficulty.
Back at Bar-4-Bar Ranches, Wasko says he’s just happy to have healthy vigorous calves running around. With bulls out for a 45- to 50-day breeding season, he aims to start calving the main cowherd April 1. Heifers start calving about March 20.
While the heifers calve close into the yard, the cow herd begins calving on pasture of stockpiled forage. “We stop feeding cows when they start calving,” says Wasko, noting the winter ration is hay and greenfeed. “Come April 1st they are out on the stockpiled forage and we check them every day or so, but rarely is there any calving difficulty. The grass looks dry, but this prairie short grass has good feed value.”
Come fall, Wasko will select replacement animals from the cow herd heifer calves, while steers and anything not needed for replacements goes into the farm backgrounding yard for winter feeding, later to be sold as yearlings or off grass the following year.