Breeding Protocol Considerations

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Source: Nebraska Cattleman Magazine

By Steven Hughes, DVM, AETA Certified, Nebraska Veterinary Services

Cattle producers have many options when it comes to breeding their cows. They can use natural service, turning the bulls they have carefully selected out with the cows that will benefit most from the genetic pairings. They can use artificial insemination (AI), allowing for a more careful and specific pairing of cows or heifers to bulls. They can also use estrus synchronization to assist in narrowing the breeding season (and the subsequent calving season) as well as to concentrate their labor inputs. When choosing a protocol, it’s important to consider time, labor, skill, cow condition and cost. Below are some considerations for each of these protocols and pointers for having the most success in your breeding season.

Synchronization Considerations

There are many protocols for estrus and ovulation synchronization. (See the sidebar for outlines of these protocols.) Most protocols require the use of hormones and specific administration timing of these hormones. Once estrus is synchronized, heat detection is important. The heat detection protocol with the lowest cost is natural heat detection using heat patches. For assistance with synchronization, consult your veterinarian or a qualified breeding service.

Conception Considerations

Natural breeding usually gives the best conception as live semen is better than frozen semen, and the bull is much better at heat detection than any human. However, natural breeding does not typically allow a producer the flexibility of using multiple sires in one group of cows. Bull-to-cow ratios vary based on pasture terrain, stocking density and bull age, with younger bulls covering fewer cows.

Poor conception rates can be very frustrating for producers and can result from poor quality semen, stress at breeding, stress at embryo implantation (15 days after breeding) or heat stress. If a cow’s body temperature climbs to 105° F for 5 minutes, fetal loss may occur. Many of the estrus synchronization protocols will bring a thin, non-cyclic cow into heat, but poor body condition may prevent pregnancy. Vaccination with a modified-live vaccine within 20 days of breeding can also negatively affect conception.

Semen Quality

Semen quality is extremely important when trying to get the best results from AI. Many producers do not have the equipment to determine the quality of a straw of semen prior to breeding. Veterinarians can determine semen quality prior to breeding a large group of cows or heifers. Semen quality varies among bulls, and young bulls often have lower quality semen compared to older bulls.

Handling techniques can also play a role in semen quality. Exposing a straw of semen to air between canes or between nitrogen tanks negatively affects semen. Many canes do not have the name of the bull on the cane top, so often, a straw is pulled out of the cane, frost wiped off to read the name and then placed back in the goblet. This action thaws the majority of the semen, then refreezes it back in the goblet. The potential result is a significant decrease in live, viable semen.

There is a very simple method to be able to safely check your semen or transfer it from one cane to another. Buy a 1-liter Igloo drink cooler and a plastic tweezer from your semen salesperson. Carefully fill the Igloo cooler with liquid nitrogen from your tank. You can now place your semen cane in the nitrogen and use the tweezer to remove the straw, look at the name on the straw while it is submerged in nitrogen, and replace it or move it to another cane. Using this method, the semen straw never leaves the liquid nitrogen and semen quality is maintained in the frozen straw.

 

Side Bar – Synchronization Protocols

Simplest Hormonal Method

  • Inject with prostaglandin and observe for heat. AI 12 hours after heat is observed.
  • Approximately two-thirds of the cows should come into heat on days 2 to 5 (72 hours most common), and heifers on days 1 to 5 (48 hours most common).

Select-Synch Method

  • Inject gonadotropin-releasing hormone (GnRH) at day 0.
  • Inject prostaglandin at day 7 with heat patches applied for heat detection.
  • Expect an average 60 percent conception on timed AI, depending on semen quality and technician skill.
  • Two injections add expense and time to the protocol but may reduce time to breeding with lower expense than other protocols.
  • If semen cost is high, timed AI may be too expensive, making heat detection a better choice.

Synchronizing Heifers

  • Option 1: Feed melengestrol acetate (MGA) for 14 days, then give prostaglandin 19 days after MGA removal. Heat check heifers or use timed AI.
  • Option 2: Use concentrated intra-vaginal drug release (CIDR) placed on day 0 and removed on day 14. Give prostaglandin 16 days after CIDR removal. Heat check heifers or use timed AI.
  • Expect an average 75 percent conception, depending on semen quality and technician skill.
  • Both protocols require more time and preparation.
  • MGA intake may vary between heifers, causing inconsistent results.
  • CIDRs may cause vaginitis or adhesions in small heifers, also leading to inconsistent results.

7-Day CO-Synch+CIDR Protocol

  • Has become the gold standard for cow synchronization.
  • Inject GnRH on day 0 and place CIDR.
  • Remove CIDR on day 7. Give prostaglandin injection.
  • Timed AI heifers at 50 hours and cows at 60 hours post CIDR removal.
  • Provides approximately 80 percent response from cows.
  • Conception similar to other protocols.

7 and 7 Synch Protocol

  • Relatively new protocol, adding 7 days to previous protocol.
  • CIDR placed on day 0. Give prostaglandin injection.
  • Give GnRH on day 7.
  • Remove CIDR on day 14. Give second prostaglandin injection.
  • Timed AI heifers at 50 hours and cows at 60 hours post CIDR removal.
  • Inject second GnRH at breeding.
  • Can provide up to 95 percent response from cows, higher than most other protocols.
  • Expect 60 to 70 percent conception, depending on semen quality and technician skill.
  • Requires the most time from initiation to breeding and multiple trips through the chute.
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