Reproductive tools for cattle evolve over 50 yearsWritten by Saige Albert
Seidel is a distinguished professor in biomedical sciences at Colorado State University and has worked with reproductive biology for many years.
“If we look at the reproductive management of cattle early in the 20th Century, it only involved buying a neighbor’s bull that had a superior phenotype, but there was limited genetic information about that animal,” said Seidel. “I’m afraid that some beef producers still do that today. What is different is that the animal is likely genetically superior due to A.I. and a breeding season.”
The priorities of any reproduction program are getting the cow pregnant, improving genetics, increasing convenience efficiency and trying something new, according to Seidel, and reproductive technologies help to achieve those goals.
“More than 50 years ago, there was no frozen semen and nothing was disposable,” commented Seidel. “I washed lots of glass syringes and plungers, and we didn’t have disposable needles, so we reused and sharpened them. Even the sleeves for A.I. were rubber, and we washed them.”
“We didn’t have EPDs or estrus synchronization, we didn’t use embryo transfer, and we didn’t even have ear tags,” continued Seidel. “The top 10 reproductive tools that we use have evolved over the last 50 years.”
Seidel described artificial insemination (A.I.), electroejaculation, vaccination programs, cryopreservation for semen, body condition scoring, hormones for synchronization, EPDs, ultrasonography, sperm sexing and genomics as the top 10 routine reproductive tools.
“When I look at these tools, the most important ones and the ones that many of you are using are vaccination, electroejaculation, body condition scoring and EPDs for bulls,” said Seidel. “Without these foundational tools, the other razzle-dazzle reproductive tools aren’t very valuable,”
The “razzle-dazzle” tools that Seidel referred to are the niche research tools that are used.
“These niche tools may not be as important for production purposes, but as is obvious, the research niche tools progress to routine use,” said Seidel. “Some of these tools evolve slowly. For example, estrus synchronization took a long time to reach a practical use level. Some of these tools go from research to application quite rapidly, such as genomics in dairy cattle, however, took only about two years to the point that now you cannot sell a bull without a genomic profile.”
The top 10 research tools that Seidel sees are hormone assays, superovulation, nonsurgical embryo recovery and transfer, cryopreservation of embryos, invitro fertilization, splitting embryos, trans-vaginal aspiration, embryo biopsy, nuclear transfer cloning and transgenics.
“In my opinion, A.I. is the most powerful genetic tool when using genetically superior semen,” Seidel said. “The big combo is ovulation synchronization with hormones, plus A.I. with a superior semen.”
Seidel also noted that the term “estrus synchronization” is now largely obsolete, and rather ovulation synchronization is preferred.
Combining these tools with frozen semen, hormones to induce cycling in post-partum cows and heifers around puberty, EPDs and genomics gives producers the benefits of genetic superiority.
“The benefits of genetic superiority are that you get your cows pregnant earlier, you can select for convenience traits and concentrating calving,” added Seidel.
“There is also a place in some situations for induced calving,” said Seidel, explaining that by giving a cow dexamethasone, calving will occur within about 60 hours.
Seidel also sees ultrasonography as a powerful tool for pregnancy diagnosis and to sex fetuses, as well as to determin ovarian status and diagnose pathology.
Among the other niche tools Seidel described the ability to sex sperm, or determine whether they will contribute an X or Y chromosome to the egg.
“Sex is the most important genetic trait, and one of the things I have worked on over the last decade is sexing sperm,” said Seidel. “The equipment used is very sophisticated and impressive.”
To sex sperm, a machine produces 80,000 droplets per second, with about one in three containing a sperm. Detectors make 180,000 measurements per second, consecutively, to evaluate whether the sperm is X or Y bearing sperm.
“The detectors are making these measurements while the sperm go by at 50 miles per hour,” continued Seidel. “When you integrate all that information, the rates can exceed 5,000 sperm per second of each sex at about 90 percent purity.”
The end result is about 15 million sperm per hour. However, with a machine cost of over $500,000, Seidel noted that it is not currently economical.
“Sexed sperm costs about $20 more per dose and has a lower fertility. It requires excellent management, but the calves are normal,” said Seidel. “The pregnancy rates were 10 percentage points lower with sexed semen, meaning you have 20 percent fewer pregnant cows.”
Other reproductive technologies include micromanipulation of embryos, including transgenesis and embryo splitting.
“We can add genes, delete genes or correct genes with transgenesis,” explained Seidel. “Currently 90 percent of corn and soybeans are transgenic, but zero percent of cattle are. We have a great aversion from a national standpoint to applying these technologies to animals.”
Seidel noted that it could be very useful for encouraging more efficient growth or polling a strain of cattle by removing the gene for horns. There are also applications that may give cows the ability to produce pharmaceuticals in their milk.
Embryo splitting involves utilizing a micro blade to sever the embryo.
“We have developed a technique to literally chop embryos in half,” said Seidel. “We made two embryos out of one, and the big advantage is you have twice as many embryos, and we increase the number of calves produced by 50 percent. We also get identical twins, which are very valuable for research.”
There are a number of other technologies on the horizon based on reproductive technologies. Seidel described utilizing sexed semen and embryo transfer to eliminate the cowherd.
“If we do beef production without a cowherd, each heifer replaces herself with a female calf. We wean at three months and fatten, then you sell the cows,” explained Seidel. “You have the whole system with no cowherd and a huge opportunity for improving efficiency.”
Seidel commented that reproductive technologies are limitless and have the potential to dramatically influence the future of the cattle industry.