The use of artificial insemination has become an integral part of commercial and purebred cattle businesses for many years. To make that possible, cattle owners need frozen bull semen either from their own bulls or purchased from someone else.
Producers who own bulls with superior genetics often want to preserve that gene pool for as long as possible. Aside from letting him naturally sire calves on the farm or ranch those genetics can be preserved for later use through collection of semen for use in artificial insemination.
Rocky Mountain Sire Services, Inc. (RMSS) at Bennett, CO, is one of several companies in the livestock industry that collects, sorts, freezes and stores semen for bull owners. Located roughly 30 miles east of Denver, the facility houses a number of “resident” bulls as well as animals that come in for shorter periods of time between on-ranch breeding seasons. Here you will find semen for cattle from A to Z—Angus to Zebu, as well as for rodeo bucking bulls.
RMSS does not sell bull semen; it is a facility for collection, sorting, freezing and storing. Lee Creech, General Manager, said there are approximately 1 million units of semen stored onsite. He likened the business to a manufacturer where they “make” a product based on the need or orders from customers. RMSS is a privately-held company with a stated mission to “provide cattlemen with a place to get their bulls collected where they can expect the highest conception rate possible.”
Kent Gross, production manager at RMSS, told WLJ that prior to arrival owners of bulls will contact the company to discuss the number of units they would like. Additionally, they determine if health testing is necessary for domestic or international sales and shipment. RMSS follows protocols established by Certified Semen Services (CSS), a division of the National Association of Animal Breeders. These minimum health requirements are designed to protect the health of bulls already resident in stud and to ensure that semen collected from these bulls is not capable of transmitting any disease.
The bulls are separated in different areas of the facility depending on the health testing needs. Gross said depending on the owner’s need, bulls may spend four to six days at the facility while others have been “in residence” for several years.
Resident bulls are typically collected twice a week, Gross explained. This will include a Monday/Thursday or a Wednesday/Friday schedule with two collections taken each of those days.
After collection the process to test and separate the semen and put it in straws for delivery to farms and ranches begins.
This is where Lab Technician Sarah Rummel steps in. Collections are brought to her lab where they are placed in a water bath to keep them at the bull’s body temperature. A small sample is extracted and run through a spectrophotometer. She explained that the machine runs a beam of light through the sample and, based on the percentage of transmittance of the light, lets her know how many cells are in the sample. “We need to know that information because that volume and concentration will tell us how many straws we can produce from that collection,” she said.
Rummel also noted that the concentration can vary from bull to bull or even sometimes from collection to collection on an individual bull. It could be, for example, a billion cells or 400 million cells per milliliter of semen, she said.
The sample then gets a small amount of antibiotic added followed by an initial dilution with an extender. Rummel said the extender includes a Tris (a chemical) and egg yolk solution. Samples are then evaluated for motility and morphology.
An interesting side note on the egg yolks: WLJ asked if the yolks were sourced from special chickens, assuming special management practices were needed and that ordinary “grocery store” eggs would not meet the requirements. Creech said grocery eggs would, in fact, work in a pinch, but to meet the demand, RMSS buys egg yolks in cartons from food service distributor Sysco and uses about 15 1-pound cartons a month.
Motility examines how mobile or active the sperm are and morphology looks at the appearance, or physical shape. RMSS determines viability by a sample that contains 65 percent or better progressive motility and 75 percent or better morphology, or normal cells. While there are many abnormalities to watch for, these conditions are determined through a count of 100 cells under the microscope. Rummel noted that any sample that doesn’t meet the threshold is destroyed. Samples that are determined to be normal are placed in a cold room to begin cooling.
Because each specimen is fragile, it is handled with care along each step including the cooling. Reducing the temperature too fast could damage cells, so the collection is placed in a cup of water, again at the bull’s body temperature to help insulate it as it cools. Rummel said it takes about an hour-and-a-half to cool the semen to 9 degrees Celsius (48.2 F). It is then taken out of the water and left in the cool room for an additional 30 minutes.
After the semen is cooled, Rummel begins adding more of the extender dilution solution before putting it in straws. Most bulls are diluted to 40 million cells per straw.
Based on the volume and concentration determined earlier, she knows how many straws are needed. That information is given to a coworker at RMSS who uses a computer program and special machine to print the bull’s identification information on each straw.
The printed straws are placed in the cool room, Rummel explained. “We don’t want to take that semen that we just spent two hours cooling and put it in warm straws.” Next, a vacuum machine is used to draw semen into the straw and to seal them using ultra-sound technology—no heat is used on the seal.
Identification and records are vitally important. The recordkeeping begins with identification labels that go with the person doing the collection. The labels are cross-referenced throughout the process, Rummel said. “We are very meticulous about that because we don’t want to misidentify—ever.”
After semen has been put in straws and cooled it is ready to be frozen. Rummel conducts an additional motility and morphology test the day after freezing to ensure the semen survived the dilution, freezing and thawing process. Again, if abnormalities are found the semen from that collection is destroyed.
At this point RMSS is not producing sexed semen. Creech noted that the demand for sexed semen is primarily in the dairy industry. “Due to the high upfront cost and lack of demand in the beef industry this far we don’t have a sorting unit,” Creech said.
Brian Stumpfhauser has the job of putting the straws in canes. These are metal pieces that hold two “goblets,” each holding five straws of semen. Again, quality control is closely monitored to ensure the stamp on the straw matches the paper report that he uses.
The goblets are placed in large liquid nitrogen tanks, each capable of holding up to 99,000 units.
The semen is now ready for the bull owner to pick it up or to be shipped to farms and ranches. As noted, RMSS does not market or sell the semen; the orders come from individual breeders or companies like Select Sires.
RMSS has three sizes of shipping containers holding 120 to 2,700 units of semen. Stumpfhauser explained that the shipping tanks are just temporary storage but will keep semen frozen for 14 to 21 days. Once the shipping container arrives, the cattle producer moves the straws to a liquid nitrogen tank and returns the container to RMSS.
Owners of exceptional bulls can definitely extend a bull’s genetic life through semen collection and freezing. Additionally, older bulls that may be injured and no longer able to effectively “work” in the pasture can still be collected, ensuring his genetics will be available for years to come. — Rae Price, WLJ editor
