Economics of timed artificial insemination with unsorted or sexed semen in a high-producing, pasture-based dairy production system.

Discipline: economics Keywords: timed artificial insemination, sexed semen, bio-economics, stochastic model.

In seasonal-calving pasture-based systems, the effect of poor reproductive performance often manifests in an increased spread in annual calving, resulting in shorter lactations and suboptimal matching of pasture supply to peak feed demand. Additionally, the long-term genetic gain may be diminished in less fertile herds due to a lower selection intensity, as a greater proportion of heifer calves must be retained as herd replacements. Timed artificial insemination (AI) facilitates maximum submission rate on the first day of the breeding season of such systems, thus improving the subsequent calving profile, whereas the use of sexed semen can increase the selection intensity by decreasing the proportion of females required to produce a target number of dairy replacement heifers. However, the percentage of females that become pregnant from a single AI event resulting from sexed semen, has been shown to be consistently lower than that of unsorted semen, thereby increasing the costs associated with breeding and culling. Nevertheless, sexed semen and timed AI may complement each other, with timed AI removing the need for labour intensive and potentially erroneous oestrus detection, and sexed semen increasing the rate of genetic gain through increased selection intensity on the dam side. Therefore, combined application of both technologies could return a higher profit advantage compared with that achievable from using either in isolation. In a study by Dr D.P. Walsh and colleagues in Ireland, the outcomes and economics of timed AI with unsorted or sexed semen in a pasture-based system were further investigated. Their results were published in the Journal of Dairy Science, Volume 105 of 2022, page 3192 to 3208, the title of the paper being: Economics of timed artificial insemination with unsorted or sexed semen in a high-producing, pasture-based dairy production system.

In the study the authors used a simulation model to estimate the potential economic benefit of using timed AI in combination with conventional unsorted or sexed semen in heifers only, and in both heifers and lactating cows. These scenarios were compared with a conventional reproductive programme in which heifers and cows were inseminated with conventional unsorted semen after oestrus detection (Control). A sensitivity analysis was also used to estimate the effect of hormone costs from timed AI use on the profitability of each programme relative to the conventional.

The mean annual profit advantage over the Control of conventional unsorted and sexed semen with timed AI in heifers only, and in both heifers and lactating cows were 3.90, 34.11, 13.96, and 41.52 per cow, respectively (heifer in eventual cow terms). The combined application of both technologies showed a greater annual profit advantage on average compared with that achievable from timed AI alone. However, the risk of not returning a positive annual profit advantage varied across the scenarios with higher risk in conventional unsorted and sexed semen in heifers only, specifically a 24 and 18% chance, respectively, of not giving a positive annual profit advantage. The sensitivity analysis showed that when hormone costs increased by 10 per cow, the use in heifers of conventional unsorted and sexed semen had a 38 and 23% chance, respectively, of not returning a positive annual profit advantage. The range in profit advantage for all groups was most sensitive to the timed AI pregnancy rate and the heifers versus heifers and lactating cow groups were most sensitive to the relative fertility achieved with sexed compared with unsorted semen.

The results of the study suggested that timed AI and sexed semen are complementary technologies that can increase genetic gain and profitability in a pasture-based, dairy production system.