Cost and Other Risks Associated with Natural Service Sires

Posted: February 6, 2006

Based upon a survey of Pennsylvania dairy producers, the major reasons listed by those who do not use artificial insemination for their heifers are the perception of lowered conception rates with artificial insemination (AI), difficulty or time involved with estrous detection, location of heifers was inconvenient for reproductive management and lack of restraint facilities.

Estrous synchronization programs have been used for 25 years and are being refined to minimize time spent for estrous detection and to manage an AI program for heifers that are located some distance from the main dairy facility. Acceptable conception rates can be achieved with properly designed and implemented programs. For a relatively small investment most heifer facilities can be upgraded and equipped to provide restraint and handling facilities for heifers. In addition to administering treatments for estrous synchronization and insemination, such facilities can also be used for vaccination, deworming, pregnancy examinations, and perhaps embryo transfer. There are solutions to the major reasons dairy producers do not use AI for their heifers.

Artificial insemination of dairy heifers provides numerous advantages. Foremost is the opportunity to improve the entire herd's genetic merit. The use of AI-proven sires from major AI organizations generates a gain of $90-$110 in milk production per year by their offspring compared to use of natural service (NS) sires. Related to the genetic merit from the sire component is the fact that heifers born of AI matings are genetically the best animals in the herd. These AI-sired heifers provide more quality replacements and a greater opportunity to cull animals of lower genetic merit. Approximately 30 percent of calves born each year are progeny of first-calve heifers. Heifer AI has a major impact on genetic improvement of the entire herd. Furthermore, calving ease information is available for AI sires. Minimizing dystocia is a major advantage of AI.

By using AI sires, dairy producers can use semen from several sires to minimize the risk of obtaining progeny from one low genetic merit sire whether from a natural service sire or an AI sire whose genetic evaluation declined as more information became available. Also, breeding dates are more likely to be recorded, calving dates more accurately predicted and appropriate dry periods planned. In a pasture-breeding situation, heifers with reproductive problems are not identified until considerable time is lost. These heifers would probably not calve at the optimum age of 24 months, resulting in lost profits.

Merchandising is another advantage for AI-sired heifers. If quality AI-sired replacements are available, then dairy producers can sell heifers based on genetic criteria. In addition, heifers tend to be the most fertile females in the herd, thus they are more likely to conceive to AI. These advantages document the tremendous opportunity that exists with use of AI for heifers.

The fact that the AI sires are examined and tested for reproductive soundness and disease, and that semen quality and fertility are routinely monitored are additional benefits. Based on the results of breeding soundness examinations performed on sixty-six on-farm dairy bulls by one veterinary clinic in California, 26 percent of the bulls were considered unsatisfactory. Breeding to a subfertile or infected natural service sire will cause a significant delay in the interval to conception. Heat stress impacts bull fertility which can significantly setback herd reproductive performance.

The most frequently asked question is “what is the comparative fertility when lactating cows are bred by AI or NS?” As you can imagine, conducting well controlled studies to answer this question are difficult. However some comparisons from field studies have been summarized. Results from three studies conducted in Australia, Europe and California showed that AI breeding was equal or superior to natural service. In the European study, fertility of 20 pairs of cows bred either by AI or NS within a 600 cow herd were compared. After three years the AI group had a shorter calving interval of 18 days. In field study within one large California herd showed that 52% of the cows in the bull bred string (pen) were pregnant compared to 60% of the cows in the AI string.

Recently the results of a comprehensive economic partial budget analysis comparing costs associated with NS and AI was conducted using data from large western dairy herds (University of California Davis, reported in Theriogenology
64, 2006). The investigators included explicit and implicit costs. Explicit costs were defined as out-of-pocket or accounting expenses involving actual cash payments, i. e., daily feed costs. Implicit costs were opportunity costs of lost milk yield and genetic improvement. For the natural service herds, it was assumed bulls were used exclusively for reproduction and managed using a rotational system. Health costs included breeding soundness examinations (BSE), blood testing, vaccines, veterinary care and foot trimming. Feed and labor costs were included. The AI herds used a modified Presynch/ Ovsynch ovulation control timed breeding program. These herds used 25% young sires and 75% proven sires with the maximum Net Merit $ of $500. There were numerous other expenses included for both groups. The model estimated the use of natural service sires in these herds averaged approximately $10 more in costs per cow/year compared to the AI program. The analysis was run numerous times over a three year period to account for changes in costs. Approximately 60% of the time, AI was predicted to cost less than NS. It should be noted that the natural service sires received BSE and routine vaccinations.

Another index that is useful in comparing the economic merit of sires is Expected Net Return dollars, ENR$, developed by Dr. Gary Rogers$/. It is a tool that puts a dollar value of revenue for one unit of semen for a sire relative to a service from an average non-AI bull. ENR$ considers the cost of semen, relative conception rate, revenue and costs associated with daughters and future generations. It is also affected by a dairy producer’s level of herd management and milk market.

So here is the take home message: there are significant costs and risks associated with natural service that may not be realized and should be considered by dairy producers using natural service for heifers or lactating cows. Secondly, and most importantly, it is your responsibility to provide a safe working environment for your employees and family members. Bulls are dangerous.

Michael O’Connor, Dairy and Animal Science Extension