Artificial Insemination Offers Opportunity to Rapidly Increase Genetics
By Scott Lake, UW Extension Livestock Specialist
Advantages of AI?
As calving season starts to wind down, the days begin to warm up and the grass begins to green, it’s time to start making plans for the upcoming breeding season.
Decisions regarding bull purchases have either already been made or are quickly forthcoming. However, artificial insemination (AI) is one of the fastest and most economical ways to improve the genetics of the cowherd. Utilizing AI allows managers to select for genetically superior animals that would be cost prohibitive to buy. AI also allows producers to select proven bulls with much greater accuracy than yearling bulls, an important consideration for heifers. In addition to low birth weights, it is possible to select for those “curve bender” bulls that combine both calving ease with high growth and carcass potential.
The majority of beef producers that do utilize AI do so only on their heifers. However, the real value of AI lies within selecting superior bulls for a mature cowherd. This requires additional management complications (separating cows and calves), however, AI-ing the mature cows provides an opportunity to select for high performing bulls without being as concerned with birth weight.
One of the major advantages of synchronization and AI is not only calves with superior genetics, but they are also born earlier in the breeding season. Research from Virginia Tech University has reported that for every day later in the calving season a calf is born, it costs the producer between $1.50-1.65/head/day (depending upon markets). Additionally, it’s hard to put a value on the uniformity of calves, but when 65 percent of the calves are conceived on the first day of the breeding season, and the majority of the remaining calves are conceived within the next 21 days, because cows were synchronized and given a jump start with progesterone, a tighter calving interval results in a more uniform calf crop, which should be sought after by cattle buyers.
Additional advantages of AI are the reduction in bull power required on the ranch. This not only reduces the total amount of money spent on bulls, but also the yearly cost of maintaining and feeding bulls.
Disadvantages of AI?
For all the benefits of using AI, there are some disadvantages, as well, such as adequate working facilities, easily accessible pastures, increased handling of cattle, technical expertise and increased time and labor. For most AI protocols, cattle must be worked at least three times within a fairly short period of time (10 days). This requires adequate handling facilities to work cattle quickly, efficiently and in a low stress environment.
Labor is usually the biggest reason that producers do not AI cattle. It takes significant labor to work cattle numerous times within a short period of time. Probably the most time consuming portion, however, is heat detection. To properly watch heat, it takes commitment. If your heat watch routine is to watch for an hour first thing in the morning and again last thing in the evening, then you will probably not achieve the success in your AI program that you would like. Research has shown that over 50 percent of heifers may come into heat in the middle of the night or at midday. Therefore, heats should be checked the majority of the morning and the majority of the evening. For many combined farming and ranching operations, heat detection and AI occurs at one of the busiest times – during field preparation, planting and early irrigation runs.
Arguments are made that suggest synchronizing the herd will result in a need for additional bulls because those females that did not breed will all start cycling again within a short period of time. Most reproductive physiologists will tell you that a bull can breed the same number of cows in a very short period of time as he can over a longer, normal breeding season. However, the limiting factor will be the size of the pasture. Will he be able to cover the ground needed and find those “heats” in a short period of time, and will he breed one cow and move on, rather than stay with that one cow.
Timed AI
To reduce labor and eliminate the need to heat detect, timed AI protocols have been developed. The theory behind a timed AI protocol is that the majority of your females will be synchronized to ovulate within a short window of time that will allow for a mass breed without the hassle of watching heats. Recent advancements in synchronization protocols have improved so much that timed AI can be nearly as effective as breeding off of heat synchronization
There are many options for synchronizing estrus in heifers or mature cows. This article is not meant to be a comprehensive list of protocols, so I will briefly discuss what types of options you have.
For beef heifers, there are several options that can deliver acceptable results. For very well developed heifers that are cycling, a two-shot prostaglandin protocol is inexpensive and requires relatively low labor. However, we highly recommend that a progestin (melengesterol acetate or MGA, progesterone releasing intravaginal device or CIDR) based protocol is used with heifers. The exogenous progesterone supplied by these protocols can help jumpstart heifers that may not have started cycling yet. The most common progestin used in heifers is MGA. One fall back with the MGA protocol is that it usually requires planning for a 33-day period. MGA will be fed for two weeks, followed by a shot of prostaglandin 19 days later, with three days of heat detection and breeding.
Acceptable conception rates can be achieved using MGA protocols, however, a concern with MGA is that, because it is mixed in the feed, it is impossible to be sure that each heifer consumes the required amount.
Other progestin-based protocols utilize a progesterone-releasing intravaginal device (CIDR). The advantages of CIDRs are that each animal is inserted with a CIDR, therefore, each heifer/cow gets its full dose of progesterone. Protocols that utilize CIDRs vary from five to seven days with three days of heat detect and AI. Therefore the entire protocol can be completed within eight to 10 days.
Both MGA and CIDR protocols use GnRH and prostaglandin to help synchronize estrus. The biggest difference between an MGA protocol and a CIDR based protocol is time and money. It takes much longer and more planning to feed MGA, however, it is more expensive to use a CIDR (~$10/head).
For producers who are interested in breeding heifers or cows off of heat, good results can be obtained with any number of protocols (MGA, seven-day Co-Synch + CIDR, five-day CIDR). It probably makes the most economical sense to synchronize with MGA if you plan on breeding off of heat. However, if you will breed cows/heifers from a strict timed AI protocol (no heat detection), using protocols that more tightly synchronize estrus response will yield greater results. In our experience, the five-day CIDR protocol consistently delivers the best results in a timed AI protocol.
Synchronization without AI?
Some producers would like the advantage of synchronizing cows to tighten calving intervals and jumpstart their cows without the hassle of AI. There are certainly advantages to simply having a more uniform calf crop, regardless of genetics, as discussed above. We would recommend an MGA-based protocol to minimize expense, while still gaining the advantage of utilizing a progestin based protocol. A simple and inexpensive approach is to give one shot of prostaglandin and turn bulls out. Because of the nature of the estrus cycle and prostaglandin, roughly 33 percent of the heifers/cows will not respond to one shot. Much better results will come from a two-shot prostaglandin protocol (given 10 to 14 days apart) with bulls turned in following the second shot.
One final note
Success in any of these protocols will depend, to a large degree, on how strictly the protocols are followed. Make sure to administer the proper doses of prostaglandin, MGA or GnRH. Make sure schedules are followed, and if breeding off of heats, make sure plenty of time is allotted to watch for signs of estrus.
No matter how well you follow protocols, which type of protocol you use or how good of an AI technician you are or hire, nothing will make up for under-nutrition. Cows should be fed to have a body condition score between a 5 and 6 at breeding. Lower than a 5 and greater than a 7 will result in reduced conception rates.
For more information on the value of AI or to discuss specific protocols in depth, contact either Scott Lake at scotlake@uwyo.edu or Steve Paisley at spaisley@uwyo.edu.
