Spaying heifers is a management tool that’s nearly a century old. It involves surgical removal of the ovaries — the primary source of estrogen and progesterone in females — thus eliminating estrous cycles and pregnancies.
For heifers destined for beef production rather than calf production, spaying has distinct advantages. Spayed heifers can be grazed or fed with steers without riding activity or worrying about the neighbor’s bull coming through a fence. Plus, heifers guaranteed as open and non-cycling draw premiums from some feedlot buyers.
Daryl Meyer, a North Platte, NE, veterinarian, spays tens of thousands of heifers in several states each year. He says spayed heifers generally are calmer than their intact counterparts. “They handle more like steers. They also gain better. If everything is equal, spayed females outperform intact heifers.”
Research indicates that spayed heifers’ performance advantage extends to both pasture and feedlot. “Some feedlot managers say spayed heifers stay on feed more consistently, more like steers. Even when feeding melengestrol acetate [MGA] to intact heifers to halt cycling activity, there’s variance in feed consumption. Spayed heifers, with more consistent intake, get more consistent feed conversion.”
Like steers, spayed heifers can be implanted, and respond better to implants than intact heifers. In fact, spayed heifers that are implanted tend to have more lean tissue and deposit less fat. One study showed average daily gain response to implants was four times greater in spayed vs. intact heifers. And grazing studies indicate a 5.5% gain advantage for spayed, implanted heifers over implanted, intact heifers, Meyer says.
"A combined average of studies over a seven-year period on spayed yearling heifers showed a 2.5%-3% gain advantage, and a 0.1-0.3 lb/day gain advantage for spayed, implanted heifers, if everything else is equal,"