Can Single Layer Centrifugation with a low density colloid replace antibiotics in extenders for bull semen?
Project overview
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Short summary
The purpose of the project is to investigate whether centrifugation of bull semen through a low density colloid can remove three bacteria that are of particular concern for bovine reproduction, namely Campylobacter, Mycoplasma and Leptospira.
Background
Artificial insemination (AI) is used extensively for livestock breeding, particularly for dairy cattle and pigs. It allows rapid genetic progress, more effective use of semen from superior males, and helps to prevent the spread of disease. However, semen can be a source of bacteria since the mucosa of the reproductive tract is colonised by bacteria from the animal itself and from the environment. Therefore, regulations are in place governing the addition of antibiotics to semen extenders, stating which effective concentrations should be used e.g. EULex 2020.
Use of antibiotics – a One Health concern
However, there is growing concern about the extensive use of antibiotics in semen extenders for artificial insemination (AI), which represents a non-therapeutic use of these agents. Recent studies in our laboratory have shown that these antibiotics are associated with changes in antimicrobial resistance in the cervical microbiota of inseminated sows (Kellerman et al., 2021) and the vaginal microbiota of inseminated mares (Malaluang et al 2022, 2023), as well as an increase in stallion sperm DNA fragmentation (Al-Kass et al, 2019). The latter may be linked to early embryonic loss. Therefore, alternatives to antibiotics are needed.
A new alternative to antibiotics in semen extenders
Spermatozoa can be separated from bacteria in semen samples by colloid centrifugation(Single Layer Centrifugation, SLC) in several species e.g. boars (Morrell & Wallgren 2011), stallions (Morrell et al., 2014; Al-Kass et al, 2017, 2019) and dogs (Luño et al., 2020 ), but some spermatozoa are lost during this process. To minimise this loss, a lower density colloid can be used (Morrell et al., 2019; Deori et al., 2020; Cojkic et al, in preparation). In a comparison of low and high density colloids for bull semen, almost all of the bacteria were removed with the high density colloid and the majority could be removed with the low density colloid. Thus, these results suggest that SLC could be a good alternative to antibiotics in semen extenders. However, in this experiment, the semen samples did not contain three microorganisms that are of particular concern in cattle, namely campylobacter, leptospires and mycoplasmas.