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Animals

Animals is an international, peer-reviewed, open access journal devoted entirely to animals, including zoology and veterinary sciences, and is published semimonthly online by MDPI.
Indexed in PubMed | Quartile Ranking JCR - Q1 (Veterinary Sciences | Agriculture, Dairy and Animal Science)

All Articles (23,164)

  • Feature Paper
  • Article
  • Open Access

Olfactory Enrichment of Captive Pygmy Hippopotamuses with Applied Machine Learning

  • Jonas Nielsen,
  • Frej Gammelgård and
  • Cino Pertoldi
  • + 8 authors

The pygmy hippopotamus (Choeropsis liberiensis, Morton, 1849) is classified as Endangered by the International Union for the Conservation of Nature (IUCN). Compared to other large, threatened mammals, this species remains relatively understudied and new findings indicate potential welfare concerns, emphasizing the need for further research on the species welfare in zoological institutions. One approach to improving welfare in captivity is through environmental enrichment. This study investigated the effects of olfactory enrichment on three individual pygmy hippopotamuses through behavioral analysis and heat-map visualization. Using continuous focal sampling, several behaviors were influenced by the stimuli, with results showing a general decrease in inactivity and an increase in environmental engagement and interaction, particularly through scenting behavior. To further enhance behavioral quantification, machine learning techniques were applied to video data, comparing manual and automated behavior classification using the pose estimation program SLEAP. Four behaviors Standing, Locomotion, Feeding/Foraging, and Lying Down were compared. A confusion matrix, time budgets, and Kendall’s Coefficient of Concordance (W) were used to assess agreement between methods. The results showed a strong and moderate agreement between manual and automated annotations, for the female and calf, respectively. This demonstrates the potential of automation to complement behavioral observations in future welfare monitoring.

26 January 2026

Schematic overview of the indoor enclosures at Aalborg Zoo, showing enclosure layout, camera placement, and scent placement (locations where olfactory stimuli were applied). The female and calf enclosure includes separate wet and dry areas, whereas the male enclosure consists of a single integrated space containing both wet and dry features.

Organic Pig Farming in Europe: Pathways, Performance, and the United Nations Sustainable Development Goals (SDGs) Agenda

  • Vasileios G. Papatsiros,
  • Konstantina Kamvysi and
  • Georgios I. Papakonstantinou
  • + 7 authors

Organic pig farming in Europe is endorsed as a promising route to more sustainable livestock production, but its ultimate contribution to the United Nations (UN) Sustainable Development Goals (SDGs) is a contested matter. This study takes a critical perspective on the potential of organic pig farming to contribute to SDGs that may include SDG 2 (Zero Hunger), SDG 3 (Good Health and Well-being), SDG 8 (Decent Work and Economic Growth), SDG 12 (Responsible Consumption and Production), SDG 13 (Climate Action), and SDG 15 (Life on Land). Organic farming systems delivered better animal welfare outcomes and positive benefits for biodiversity, soil health, and rural employment. Continued improvements in sourcing feed, greenhouse gas emissions per unit of product, animal health, and market could improve their contributions to agricultural sustainability. This study concludes that organic pig farming does not represent a guarantee of sustainable livestock production, but it could represent credible sources of sustainable livestock innovation if sufficient policy, practice, cost accounting, and sustainable metrics are organized together to support organic systems. Organic pig farming focused on innovation and policy support can make it a role model for the transition of European livestock sector towards the 2030 Agenda.

26 January 2026

Evidence-based decision-making framework for sustainability monitoring, reporting, and benchmarking.

The critically endangered Asian giant softshell turtle (Pelochelys cantorii) is a national first-class protected aquatic animal in China, and artificial breeding is vital for its conservation. Given the pivotal role of substrate in captive rearing, this study aimed to investigate the effects of different substrate types on the growth, serum biochemistry, and behavior of juvenile P. cantorii. A total of 45 8-month-old juveniles [(121.11 ± 0.65) g] were randomly allocated to three groups (fine sand [FS], pea gravel [PG], and no substrate [NS]) for an 18-day rearing trial. Results indicated that the FS and PG groups exhibited significantly higher weight gain and specific growth rates than the NS group (p < 0.01). Serum malondialdehyde (MDA) levels were lower in the FS and PG groups than in the NS group (p < 0.05), with no significant difference between FS and PG. Notably, three individuals in the NS group exhibited symptoms of skin ulceration. No significant intergroup differences were observed in glucose (GLU), triglyceride (TG), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), or cortisol (CORT) levels (p > 0.05). Behaviorally, the FS group demonstrated the highest hidden rest frequency and duration (p < 0.01) and significantly lower active avoidance behavior compared to PG and NS (p < 0.01). In conclusion, substrate type significantly influences captive juvenile P. cantorii, with fine sand being optimal as it enhances growth, alleviates oxidative stress, and reduces maladaptive behaviors.

26 January 2026

Schematic diagram of aquaculture experiment barrel: (a) no-substrate group; (b) fine sand group; and (c) pea gravel group.
  • Feature Paper
  • Article
  • Open Access

Infectious endometritis is a primary cause of subfertility in mares. Many manuals and guidelines are available for administering intrauterine infusions of antibiotics and biofilm-disrupting solutions, detailing concentrations, vehicle solutions, and buffers. However, the stability of these combinations has not been documented. Therefore, our study investigated how factors such as storage temperature, concentration, buffer types, combinations of biofilm disruptors, and vehicle solutions affected pH stability over 24 h in uterine infusion preparations commonly used by veterinary theriogenologists to treat endometritis in mares. In experiment 1, amikacin, ampicillin, ceftiofur, ciprofloxacin, gentamicin, penicillin G potassium, penicillin G procaine, and ticarcillin clavulanate were diluted in saline and lactated Ringer’ s solution and stored at 5 ° C, 21 ° C, and 37 ° C for 24 h. Solutions were evaluated for pH and physical characteristics at 0, 1, 3, 6, and 24 h after storage. In experiment 2, 1- and 2-g doses of amikacin, ampicillin, and gentamicin were compared, evaluating the same volume at different concentrations and their stability over 24 h. Experiment 3 combined biofilm chelators (i.e., Tris-EDTA, hydrogen peroxide, and dimethyl sulfoxide) with antibiotic solutions and evaluated interactions among products. Experiment 4 compared the stability of each antibiotic diluted in saline and lactated Ringer’ s solution. Statistical analysis was performed using GraphPad Prism 9.3.0. Significance was set at p < 0.05. The results indicated that the stability of antibiotic solutions for uterine infusions in mares is significantly influenced by storage conditions and pH fluctuations. Solutions containing aminoglycosides showed an increase in pH over time, suggesting that buffering agents like sodium bicarbonate can enhance stability. In contrast, other antibiotics exhibited a decrease in pH, particularly at elevated temperatures, which may reduce their effectiveness. In conclusion, the pH stability of uterine infusions is affected by various storage conditions and vehicles, underscoring the importance of evaluating antibiotic treatments for quality control. While pH changes were observed, the potential impact on the overall stability or antimicrobial activity of the solutions requires further investigation.

26 January 2026

Comparison of amikacin solutions’ pHs between 1 g and 2 g concentrations across timepoints and temperatures. AMK + S, amikacin diluted in saline solution. AMK + R, amikacin diluted in lactated Ringer’s solution.

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Animals - ISSN 2076-2615