Breeding for | TSLN.com

Breeding for

The ability to select calf gender in a commercial livestock operation has obvious value from a number of angles: utilizing the most maternal cows to produce replacement heifers, or producing a pot load of steers versus a split load in those operations with 150 cows among them. But many questions regarding this relatively new technology also remain, and keep the majority of producers cautious when considering implementing sexed semen use into their AI programs.

Among those conducting research in an effort to answer if and how commercial cattlemen can best utilize sexed semen in an economically impactful way is University of Idaho Superintendent of the Nancy Cummings Research, Extension and Education Center John Hall and his crew.

"We were able to select a smaller number of cows – 60-70 versus 100-120 to develop replacement heifers out of. We would breed those cows one time to sexed semen, and then would clean up with maternal bulls. Right now, with that combination of one time breeding sexed semen and one cycle natural service, we are able to consistently get 65 percent female calves from that group of cows," began Hall, adding that 40-50 percent of those cows typically catch AI with sexed semen, with the balance being bull bred. Hall took advantage of being in a research center to do just that: conduct research on the various aspects of using sexed semen in a commercial setting. Additional incentive was provided by the potential benefit Hall could see as a result of utilizing sexed semen within the research center's own cowherd.

"We saw sexed semen as a way to generate more replacement females with a smaller number of cows. We calve about 325 cows annually, and being a research center means there are always a large number of people that need to utilize those cows, which resulted in the herd being made up of a variety of sources. So, in 2008 I thought we needed to become a more consistent Hereford/Angus cowherd, but at the same time we could not lose the ability of having those animals available for other research projects," explained Hall of the initial draw toward AI'ing to sexed semen in addition to researching its efficacy.

What was learned?

While the idea of utilizing sexed semen is exciting, and the potential benefits are easily identifiable, Hall said there was quite the educational curve ball attached to implementing it into his breeding program. He encouraged producers to educate themselves on the various factors unique to using sexed semen before beginning use on their operation.

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"Pregnancy rates are decreased 10 to 20 percent compared to conventional semen," Hall began of one of the major differences between AI'ing to sexed semen versus conventional semen.

Combining known lower pregnancy rates with a fledgling AI program is one thing Hall strongly suggested against. Instead, for those producers interested in using sexed semen who do not currently AI, he encouraged the use of traditional semen for the first few years until they become more comfortable with general AI practices, then implementing sexed semen into their breeding regime.

"We have also experienced a high degree of variability from bull to bull," he stated as another "need to know" aspect of AI'ing to sexed semen.

The current low number of inseminations per bull limits the ability to statistically differentiate AI pregnancy rates between bulls. This means it is currently unknown if conception rate variations are due to sorting damage, differences in bull fertility, or differences in the cows AI'd to a given bull. To combat this issue, Hall suggested using multiple sires initially, and identifying which performed best in an individual scenario before narrowing the field to one or two sires.

Fixed time AI systems work well with sexed semen, but Hall still encouraged use of estrus detecting devices to aid in maximizing conception rates.

"We suggest using an estrus detecting device or aide, such as the colored patches, and only putting sexed semen in those individuals who showed estrus prior to breeding. If she did show estrus, put sexed semen in her, if she did not show estrus, put conventional semen in her. We see a 10-15 percent increase in pregnancy rates of those individuals who have shown heat compare those who have not," explained Hall.

While cow and heifer conception rates are similar when using sexed semen, delaying insemination in fixed time AI systems will not improve conception rates in either class of females according to Hall's research.

What is next?

"The next practical application we've been working on to see if it's economically feasible is the question of whether we can use y-sorted semen one time with a fixed time AI protocol followed with natural service and convert a split load of calves into an entire pot load of steers," explained Hall.

At present, Hall is getting around 65 percent male calves, a level he calls good, but not good enough.

"For it to be economically relevant to a commercial cattlemen, that percentage needs to be closer to 70 percent steers. That's the point at which using sexed semen becomes worthwhile as an application for those cattlemen," he explained.

A "heifer heifer" system is another new aspect of utilizing sexed semen Hall is excited to begin implementation of this year.

"We are taking yearling heifers that we think would be good candidates as mothers of the next generation of replacement heifers, then we breed all of those heifers to x-sorted semen. The goal with this is two-fold – one is that by mating those heifers to x-sorted semen, we know we will get calves that have lighter birth weights than their bull calf contemporaries, which will hopefully reduce dystocia. The second is that we hope to shorten the generation interval through having our replacement heifer's produce the next generation of replacement heifers," explained Hall.

Regardless of use, sexed semen's greatest limitation from a commercial-use standpoint remains the expected 40-50 percent conception rate compared to 60-65 percent conception rates with traditional semen. However, Hall is confident that next three to five years will change that limitation dramatically.

"My opinion is that the technology and research has and will continue to validate the use of sexed semen in the commercial beef industry. Work is continuously being done to improve current pregnancy rates. If a producer is on the fence a little bit, I would suggest watching to see what the next couple years bring. I believe they will result in an increased amount of success to the degree that this tool becomes a viable option for any producer who has a quality AI program in place," stated Hall.