Ruminant colostrum management is of increasing importance in published literature due to its influence on youngstock future health and productivity outcomes, but also for its applicability as a therapeutic and metabolic parameter. The highlighted collection of recently published papers relates to ruminant colostrum and transition milk (milkings 2–6 postpartum) and reflects growing interest in this field. The collection touches on colostrogenesis (McDermott et al., Reference McDermott, Shi, Kennedy, Hogan, Brennan, O'callaghan, Egan, Nolan and Prado-cabrero2024; Stojić et al., Reference Stojić, Ilić, Kovačić, Gvozdić, Stajković, Vejnović, Savić and Fratrić2020), comparison of diagnostic testing (de Oliveira et al., Reference de Oliveira, Cunha, Ítavo, Roma Júnior, Teixeira and Dos Santos2025; Hue et al., Reference Hue, Williams, Petrovski and Bottema2021; Pisello et al., Reference Pisello, Forte, D'avino, Pisano, Hyatt, Rueca and Passamonti2021), colostrum bioactive components (Finot et al., Reference Finot, Boutinaud, Quesnel and Chanat2025; Yamagishi and Kawashima, Reference Yamagishi and Kawashima2026) and bacteriology (Denholm, Reference Denholm2026; Sun et al., Reference Sun, Wang, Hosseini Ghaffari, Lv, Xin and Ma2025).
Traditionally, publications have focussed on colostrum immunoglobulin concentration as the main measurement of colostrum quality; however, colostrum is rich in myriad bioactive compounds such as oligosaccharides, cytokines, vitamins and minerals, as well as non-specific antimicrobial peptides such as lactoperoxidase, lactoferrin and lysozyme. The beneficial function of these bioactive compounds is just beginning to be characterised. Work in the highlighted collection used flow cytometry to measure stem-like cells in colostrum in a preliminary descriptive study (Finot et al., Reference Finot, Boutinaud, Quesnel and Chanat2025). The absorption profile and effects of these stem-like cells on immunity and development of the neonate, as well as establishment of the cellular mechanisms underlying the passage of these cells into mammary secretions, remain unknown and should be the focus of future work.
As first lactation secretions transition to whole milk, the gradual change and decline in the aforementioned immune and bioactive compounds has also been the target of much recent work. Providing transition milk (or indeed extended feeding of colostrum) for the first few days of life may provide the neonatal ruminant with additional support for immune function and improved vitamin status (McDermott et al., Reference McDermott, Shi, Kennedy, Hogan, Brennan, O'callaghan, Egan, Nolan and Prado-cabrero2024). Preserving immunological and bacteriological quality may be achieved through several means, including cold temperature storage and chemical additives, all of which present practical challenges on-farm and which are captured in a review article in this highlighted collection (Denholm, Reference Denholm2022). Serial testing is paramount to understand the dynamic shifts in composition between colostrum and transition milk, and descriptive work should be supplemented with more investigation into the function of these various bioactive components both in vitro and in vivo. Optimal duration of feeding of colostrum and transition milk (including optimal immunoglobulin and bioactive concentrations) beyond the first day of life has yet to be elucidated. Furthermore, applicability of colostrum to treat neonatal ruminant diseases such as diarrhoea and especially respiratory disease should be the subject of future investigations.
Clinical applicability of indirect testing methods for immunoglobulin concentration in colostrum has been an area of much scrutiny. Individual country silos of research are commonplace, and a more ‘joined-up’ approach to research is challenging across country borders, leading to much research lacking in novelty (Haggerty et al., Reference Haggerty, Mason, Ellis and Denholm2021; Hue et al., Reference Hue, Williams, Petrovski and Bottema2021; Pisello et al., Reference Pisello, Forte, D'avino, Pisano, Hyatt, Rueca and Passamonti2021). Brix refractometry, in particular, offers a low-cost, easily accessible tool for indirect estimation of colostrum immunological quality and has been the subject of much country-specific work. Often redefining cutpoints depending on breed or geographical location makes comparison of prevalence of low-quality colostrum difficult and is therefore counterintuitive. Using reference direct testing to more accurately measure immunoglobulin and to act as a comparison for indirect methods is often lacking in published work (de Oliveira et al., Reference de Oliveira, Cunha, Ítavo, Roma Júnior, Teixeira and Dos Santos2025). Risk factors for poor colostrum quality or indeed low serum immunoglobulin concentrations in neonates are also dependent on individual country management practices, influencing the external validity of the research findings (Haggerty et al., Reference Haggerty, Mason, Ellis and Denholm2021).
Beyond the traditional investigation into colostrum immunoglobulin concentration as the primary measure of quality, bacteriology is increasingly under the spotlight. Pen side testing to determine colostrum bacteriology and promote hygienic harvest, storage and feeding practices would be a useful addition to the research field (Denholm, Reference Denholm2026). In addition, measurement of viable colonies both in colostrum and in the gut is crucial to understanding the interaction between ruminant host and gut microbiome. The optimal ruminant neonatal microbial gut profile has yet to be defined, and future work should focus on measurement of relative abundance of viable colonies rather than bacterial genetic material (which may or may not be active). Work highlighted in this series measured relative abundance of bacteria in microbial colonies in goat colostrum and transition milk by amplicon DNA sequencing, revealing predominance of Proteobacteria, Bacteroides, Firmucutes and Actinbacteria, together with an interesting shift in microbial profile between colostrum and transition milk (Sun et al., Reference Sun, Wang, Hosseini Ghaffari, Lv, Xin and Ma2025). This shift was hypothesised to be linked to the transition of the neonate from passive immunity to active metabolism with stage-dependent milk-associated bacteria, although the biological importance of this has yet to be determined.
Manipulation and optimisation of colostrogenesis or colostrum composition often includes research into various supplementations or dietary manipulations (McDermott et al., Reference McDermott, Shi, Kennedy, Hogan, Brennan, O'callaghan, Egan, Nolan and Prado-cabrero2024; Stojić et al., Reference Stojić, Ilić, Kovačić, Gvozdić, Stajković, Vejnović, Savić and Fratrić2020). The external validity of these data depends on the particular systems in which they have been deployed. Pasture-based animals, for example, may respond differently than indoor-housed animals to any attempted nutritional or supplemental manipulation of colostrum profile. This collection explores selenium (McDermott et al., Reference McDermott, Shi, Kennedy, Hogan, Brennan, O'callaghan, Egan, Nolan and Prado-cabrero2024) and zeolite (Stojić et al., Reference Stojić, Ilić, Kovačić, Gvozdić, Stajković, Vejnović, Savić and Fratrić2020) supplementation of dairy cows, with mechanisms hypothesised but not fully elucidated. Cost-benefit analysis of various interventions would also be a useful addition to this field.
While it is acknowledged that randomised controlled and prospective studies with large sample sizes on multiple farms are expensive, they are necessary to improve our understanding of colostrogenesis and colostrum management. It would also be useful for colostrum investigations to use, where possible, fresh rather than frozen samples to characterise composition and pH, particularly its link with bacteriology as investigated in one of the papers highlighted in this series (Denholm, Reference Denholm2026). It is acknowledged that this is not always possible within the confines of research resources and practicalities. In fact, much colostrum research is opportunistic in nature, employing small sample sizes and ‘leftover’ samples, which has implications for clinical applicability.
Small ruminant research is less popular than bovine work, despite many countries predominantly growing and ingesting caprine and ovine products. This could reflect funding shortages in this field, and is an area which could benefit from increasing attention. Work highlighted in this collection characterises immunological, lipid and microbial changes in a small number of frozen samples from Guanzhong dairy goats (Sun et al., Reference Sun, Wang, Hosseini Ghaffari, Lv, Xin and Ma2025), noting increases in specific fatty acid profiles (primarily stearic and palmitic) in transition milk compared with colostrum.
The findings described in the collection highlight opportunities to optimise colostrum quality measurement (especially bacteriology) and explore colostrogenesis in more detail, with a more ‘joined up’ approach from colostrum researchers in individual country silos. The highlighted work also touches on colostrum as a metabolic parameter of calcium homeostasis, which adds a new dimension and perspective to colostrum utility (Yamagishi and Kawashima, Reference Yamagishi and Kawashima2026). In general, the field is shifting from broad evaluations of bovine colostrum as a nutritional supplement toward more targeted investigations into specific bioactive components, mechanisms of action, and clinical applications. Progress will depend on well-designed, adequately powered randomised controlled trials and integration of advanced molecular science.
In conclusion, this series of collected colostrum papers provides a broad slice of the direction of colostrum research internationally. The papers emphasise the importance of understanding and characterising colostrum quality beyond immunoglobulin concentrations as well as optimising pen-side testing strategies. They further highlight the need for focused work in the small ruminant sector with larger sample sizes and purposive study designs. The collection can be found at https://multimediafluids.uam.elogim.com/core/journals/journal-of-dairy research/collections/ruminant-colostrum-research
