Vaginal spaying is accomplished through the vagina. Vaginal spaying is much faster and less stressful on heifers. It also reduces the risk of infection or other complications associated with flank spaying. In addition, many more animals can be safely spayed in a day's time using the vaginal technique, which lowers overall labor costs. As with any surgery, the experience and proficiency of the surgeon is critical.
The Ovarian-Drop method involves a small-diameter, stainless-steel rod with an arrowhead-shaped end open in the middle. When the ovaries are excised, they're allowed to drop into the abdominal cavity for absorption by the body. Harvest examination of numerous groups of heifers has revealed no re-attachment of excised ovaries within the abdominal cavity. Losses due to pregnancy
A pregnant heifer calving in the feedlot costs the feeder $150-$200 due to calving problems, infection, and decreased gain, carcass quality and yield.
A 1984 survey of feedlots and packers found almost 15.5% of feeder heifers were pregnant at feedlot arrival. The total cost to pregnancy-test and abort, or inject all heifers to abort those pregnant, averaged 5.29% of the purchase price of the heifer. This includes added charges for observation, managing dystocias, retained placentas and treatment. Unfortunately today, the incidence of pregnant heifers entering feedlots is still in the 10-15% range.
Meat packers estimate the average loss in carcass yield for pregnant heifers is 3.3%. Data on more than 10,000 heifers shows an average carcass yield decrease of 5.6% on pregnant heifers. Based on carcass weight gain, pregnant heifers gained 12.6% less and had a 13.3% higher feed conversion rate than non-pregnant heifers.
Research trials indicate spayed heifers in the feedlot — implanted and marketed at the correct time — have a 2% gain advantage compared to implanted intact heifers. The advantage is based on a combined average of studies over a six- to seven-year period on spayed yearling heifers shipped to feedlots.
The spayed heifer will reach optimum grade sooner than her intact counterpart. Cattle, both steers and heifers are being fed 130-150 days now in the feedlot phase to get them much bigger than in previous years.
It's clear that spayed heifers implanted and marketed at the proper time will outperform their intact counterparts. Feedlot operators realize these figures, coupled with potential problems of abortion, calving/dystocia problems and increased labor costs of pregnant heifers, make pregnant heifers a definite feedlot liability.
Spaying also eliminates the visual exposure of heifers calving in a feedlot setting, which can harm public perception of both the individual feedlot and the overall industry regarding animal welfare and care.
Performance after spaying
It's been reported previously that spayed heifers had a performance disadvantage compared to intact heifers. Those studies, however, all involved heifers spayed with the flank method and no use of growth promotant implants.
This isn't the case when comparing implanted spayed and implanted intact heifers. For spayed heifers, the source of progesterone and most of the estrogen source has been removed. Therefore, it's important to implant spayed heifers.
Studies show spayed heifers respond more positively to implants than intact heifers. Spayed heifers can be grazed, fed and implanted in a manner similar to steers.
One study showed the average daily gain response to implantation was four-fold greater in spayed than in intact heifers. Heifers spayed and implanted tended to deposit more lean tissue and less fat during this experiment.
Other grazing/growing studies have shown an overall 5.5% gain advantage (0.12 lbs./day) for spayed implanted heifers vs. implanted intact heifers.
Just my personal opinion after working around LOTS of cattle working facilities.
- Daryl G. Meyer, DVM