While the number of dairy replacements sired by artificial insemination (AI) has increased by 86% since 2010, the actual number of animals sired by stock bulls, while declining proportionately, has remained static since then.

The purpose of this report is to objectively compare natural mating versus AI using a cost-benefit analysis.

Across both AI and natural mating, the revenue of a sire will be determined by his male and female progeny’s EBI.

Data for calves born in 2021 is presented in Table 1. The results clearly show a higher average EBI in the AI sires compared to that of the stock bulls.


Also, the average reliability of the EBI of AI sires is considerably greater. Average genetic merit for milk, fat, protein, calving interval and survival are superior in the AI sires.

An additional analysis was undertaken on the actual daughter performance of stock bulls or AI sires producing in Irish milk-recorded herds.

The data presented in Table 2 shows the milk production and calving interval of AI- or stock bull-sired first, second and third or greater lactation cows in 2021.

For a herd of 100 cows with a 25:22:53 first, second and third cow parity structure, the average AI-sired herd is expected to be €14,436 more profitable than the average stock-bull-sired herd (assuming a similar parity structure).

Artificial insemination

  • Semen cost: the costs assumed are €28 per insemination for the first insemination (including technician service) plus a callout fee of €7 per day for the first three weeks of the breeding season. Repeat charges are €12 per head including technician service. This amounts to a cost of €45.83/cow (including 0.25 heifers per cow) or €4,583 for a 100-cow, 25-maiden-heifer breeding season.
  • Heat detection: the recommendation is to observe cows at least three times daily (including each milking) with the aid of tail paint. Tail paint amounts to an annual cost of €7/cow. This amounts to a cost of €700 for a 100-cow, 25 maiden heifer herd. Thus, the annual cost of AI and heat detection is €5,283 in a 100-cow herd.
  • Stock bull

  • Capital and variable costs: an average price assumed for a stock bull is €2,500 which, spread over 18 months following a sale price of €1,200, amounts to €781.25/year assuming an annual interest rate of 7% on the purchase price. Feed costs were assumed at €400/year, with an annual veterinary/hoof-paring cost of €50/year. Annual overheads, labour and housing costs sum to €250, bringing annual costs to €1,481.25 for a stock bull.
  • On average, a stock bull will annually serve 30 cows (including repeats). This amounts to a cost of €49.38/cow but this is based on optimal efficiency in terms of bull-to-cow ratio.
  • Infertility: a large cost associated with stock bulls is the risk of infertility. Around 10% of bulls are expected to be infertile at some stage of the breeding season. Although such frequency is also possible in AI sires, each ejaculate is assessed for semen quality so the risk of infertility is minimised.
  • Safety: another cost associated with the stock bull is the associated danger, especially with older farmers and farmers with young families. From 2011 to 2020, stock bulls on Irish farms killed seven people. The level of non-fatal accidents caused by stock bulls is less accurately recorded but is undoubtedly high. No cost can be put on human life.
  • Biosecurity: the introduction of any animal into a herd increases the risk of introducing disease.
  • Lack of flexibility: the use of one stock bull does not allow for assortive mating. For example, a cow extreme in one trait may not be corrected if the majority of the herd are of the other extreme and the stock bull is chosen to correct the average of the herd. Using a dairy breed stock bull does not facilitate the mating of later-calving cows to a beef breed without also using AI or purchasing an extra stock bull.
  • In summary, the cost associated per cow with using a stock bull assuming a lifespan in the herd of two years, a purchase price of €2,500, salvage value of €1,200 and a bull-to-cow ratio of 100:4 in a 100-cow herd is €59.25.
  • This increases by 25% to account for the 25 replacement heifers reared to a total of 74.06 per cow or a total of €7,406 per annum.

    This may be considered a conservative estimate.

  • A recent analysis of stock bulls used in 2020 indicates that they are recorded as the sire of an average of 18.4 calves per herd per annum.
  • The cost may increase as the number of cows varies between multiples of 30, if the bull dies on farm, if the cost of the stock bull increases and/or the salvage value of the length of period of use decreases.