One of the most significant challenges in deer is the ability to maintain genetic diversity, avoiding inbreeding and sustaining population health and reproduction. Although our general knowledge of reproductive physiology is improving, it appears that the application of assisted reproductive technology (ART) will more efficiently advance wildlife conservation efforts and preserve genetic diversity. The purpose of this review is to present the most important results obtained with the use of ART in Neotropical deer. Thus, the state-of-the-art for estrus synchronization, semen technology, artificial insemination, and in vivo embryo production will be presented. In vitro embryo production (IVP) is also a biotechnology that is taking initial steps in deer. In this aspect, the approach with the proteomics of ovarian follicular fluid is being used as a tool for a better understanding of oocyte maturation. Finally, cell banks and the use of interspecific somatic cell nuclear transfer (iSCNT) as well as the use of stem cells for gametes differentiation are promising techniques.

In recent years the concept of genomic resource banks has grown as a way of maintaining the genetic variability of populations, while the quality of cryopreservation of the gametes determines the effectiveness of such banks. However, the absence of basic knowledge regarding the physiology of species and their semen characteristics hampers the establishment of reproductive biotechnologies. Thus, this paper aimed to determine certain physicochemical (volume, colour, appearance, pH and osmolarity) and microscopic characteristics (mass movement, motility, vigour, concentration, and sperm morphology and morphometry) of semen of the species Mazama americana. To achieve this, five males of the species were used, and three semen samples per buck (electroejaculation) were collected at intervals of 2 weeks. The volume, pH and osmolarity of the ejaculate were 0.39 ± 0.14 mL, 6.90 ± 0.74 and 297.74 ± 19.10 mOsm/kg, respectively, while the values obtained for mass movement, motility, vigour and concentration were 3.33 ± 0.82; 69.6 ± 8.92%; 3.53 ± 0.50, and 244.07 ± 98.65 × 107/mL, respectively. Regarding the colour of the ejaculate, five samples were classified as ivory, two as yellowish, two as whitish and six as white. Regarding appearance, seven samples were considered creamy and eight, milky. Morphology was analysed in a humid chamber under phase contrast microscopy and 73.50 ± 5.57% of cells presented normal morphology, 8.37 ± 3.15% presented major defects and 18.13 ± 6.46% presented minor defects. To determine sperm morphometry, an optical microscope (Leica DM 5000B) and the Leica Qwin image analyser program were used, resulting in 8.09 ± 0.40, 4.65 ± 0.30, 2.81 ± 0.44 and 30.25 ± 3.02 µm for length, largest width, smallest width and area, respectively.

In vitro production of embryos has gained prominence as a tool for use in wildlife conservation programmes in situ and ex situ. However, the development of this technique depends on steps that include ovarian stimulation, collection and oocyte maturation. The purpose of this study was to assess the feasibility of an ovarian stimulation protocol for follicular aspiration, the efficiency of videolaparoscopy for follicular aspiration and test a medium for in vitro oocyte maturation for the species Mazama gouazoubira. Five females were submitted to repeated ovarian stimulation (hormone protocol using controlled internal drug release), and estradiol benzoate on D0 and eight injections of follicle-stimulating hormone, once every 12 h, from D4 onwards at 30-day intervals. Fourteen surgical procedures were performed in superstimulated females, resulting in the collection of 94 oocytes and an average of 17.1 ± 9.1 follicles observed, 13.5 ± 6.6 follicles aspirated and 7.2 ± 3.7 oocytes collected per surgery. After collection, the oocytes were submitted to in vitro maturation for 24 h and stained with Hoechst 33342 dye to evaluate their nuclear status; 64.5% of the oocytes reached MII and 16.1% were spontaneously activated by parthenogenesis. The nuclear status of oocytes that did not undergo in vitro maturation was evaluated; 80.9% were found to be immature.

The Neotropical region is currently facing a critical period of biodiversity loss, with deer species (family Cervidae) being particularly affected by severe habitat degradation, genetic bottlenecks, and population fragmentation. In this context, germplasm biobanks emerge as strategic tools for conservation efforts. This article presents a comprehensive review of the Deer Research and Conservation Center germplasm bank, the largest repository of genetic material for Neotropical deer worldwide. We detail the diversity of species represented, the types and quantities of cryopreserved samples, and the operational costs associated with maintaining the biobank. Additionally, we discuss the main advantages of germplasm banking, such as preserving genetic diversity without the logistical challenges of managing large captive populations, as well as critical challenges, particularly those arising from ongoing taxonomic uncertainties that complicate species identification and sample management. Scientific applications and conservation actions already enabled by this resource are presented, alongside a discussion of future perspectives, including potential expansions of sample types and integrative genomic analyses. This review underscores the essential role of germplasm biobanks in preserving the genetic legacy of Neotropical deer and supporting long-term biodiversity conservation strategies.

Considering the taxonomic uncertainties of Neotropical deer species, as well as the threat status of many of them, new studies and strategies for their maintenance are urgently needed. Obtaining live cells is of great importance for the conservation of wild species in order to allow cytogenetic and molecular studies to be carried out and for the construction of genomic resource banks. In order to increase the genetic diversity stored in these banks, the possibility of collecting skin fragments from dead animals (e.g., run over, hunted, deaths related to disease or natural causes) becomes a valuable source and a last alternative for obtaining material from these individuals. However, the interval between the death of the animal and the collection of tissue can directly interfere with the quality of the sample obtained and it is therefore essential to identify the maximum time during which viable cells are still found. Thus, this study sought to establish a protocol for the collection, storage, cryopreservation, and cultivation of skin obtained postmortem from individuals of the species Subulo gouazoubira (gray brocket deer) and Mazama rufa (red brocket deer). The collection of tissue fragments at different postmortem intervals (0 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, and 11 h) was evaluated. The tissues were analyzed for fibroblast cell viability immediately after collection. Their ability to undergo cryopreservation was evaluated based on techniques that can be directly applied to samples obtained in the field and their subsequent thawing and success of cell cultures was performed in the laboratory. Regarding the genetic integrity of the cells, the number of metaphases was observed by the mitotic index. The cell viability presented by the samples always remained above 60%. It was possible to establish cell cultures even with the tissues obtained 11 h after the death of the individuals; however, they required twice as many days to reach bottle confluence compared to the cultures performed with the tissues obtained 0 h after the death of the individuals. The results suggest that the best rates of cell viability, time to reach confluence, and number of metaphases per cell (mitotic index) are found in skin fragments collected up to 5 h after the death of individuals when their carcasses are kept at room temperature.