Ludovic Calandreau

Background: While epigenetic variations can contribute to shaping phenotypic diversity, it can be challenging to isolate and quantify the portion of trait variability under non-genetic influence. In this study we compared the phenotypic responses for different traits of two epilines of Japanese quails ( Coturnix japonica ) across three generations, using a large sample size. These epilines were built in parallel following (epi +), or not (epi -), an initial genistein ingestion in the ancestors' diet and were maintained to harbour a similar genetic structure. Results: Linear models were fitted to extract the fraction of variance allocated to multiple factors such as family, sex and epiline. The latter was found to be significantly associated with body weight. The contribution of the epiline to phenotypic variability progressively increased from the first generation (G0) to the last (G2), leading—for example in body weight at slaughter—to an average difference for adult males and females in G2 of 9 g and 14 g respectively, between epi + offspring and controls (epi-). Conclusions: Although these findings suggest genetic drift, they could also reveal a possible transgenerational effect of the initial diet disruption. The analysis of other phenotypes displayed rare significant effects of the epiline. This innovative experimental design offered a unique opportunity to better understand the evolution of phenotypic variability and the parameters constituting it across three generations following or not an environmental change.

The ability to perceive and interpret emotions from others provides clear evolutionary advantages for social animals. Domestic animals live in close contact with humans, making human emotional cues particularly relevant for them. Understanding how these animals recognise, memorise, and respond to human emotional signals is therefore crucial to investigating their cognitive capacities and their active role in interspecific social interactions. Thus, this study investigates whether cows can discriminate between human expressions and use this information to guide their behaviour in a subsequent choice test. Thirty-nine cows were shown two 30-second videos: one of an experimenter expressing joy and another expressing anger through facial and vocal cues. Afterward, both experimenters simultaneously presented themselves to the cows in a choice test. During video exposure, cows looked longer at the anger video and showed a left-eye bias, suggesting right-hemisphere processing of negatively valenced stimuli. They also displayed more behaviours indicative of a negative perception. In the subsequent choice test, cows spent significantly more time close to the experimenter who had previously expressed joy. These results demonstrate that cows can discriminate and remember human emotional expressions and use this information to guide their choices in future social interactions. This highlights their role as active participants rather than passive observers in interspecific relationships, and provides insight into contexts where such abilities may be expressed, with potential implications for enhancing human–animal relationships and welfare.

Variation in mitochondrial aerobic metabolism has been suggested to underlie variation in interindividual performance. Mitochondrial efficiency quantifies, directly or indirectly, the amount of adenosine triphosphate (ATP) produced relative to O ₂ consumption. High mitochondrial efficiency is theoretically beneficial by providing more ATP per amount of resource consumed, but may come at the cost of increased reactive oxygen species (ROS) production damaging tissues through oxidative stress. Mitochondrial efficiency is a plastic trait but how it changes through postnatal development remains unknown. We hypothesized that strong selective pressure could lead to an increased mitochondrial efficiency to support fast growth but incur an oxidative cost. We tested this hypothesis by quantifying mitochondrial aerobic metabolism, efficiency and ROS production through postnatal growth in Japanese quail ( Coturnix japonica ), in two highly aerobic tissues: skeletal and cardiac muscles. Mitochondrial efficiency was indeed higher during peak growth in both tissues, but this was surprisingly associated with markedly lower ROS production. This high efficiency was likely achieved via both a lower proton leak and a higher contribution of complex I to respiration. These results show that enhancing mitochondrial efficiency may be important to support growth, but suggest the presence of unexpected ROS mitigation processes during early-life growth.

Social recognition has been studied and demonstrated in many species. In domesticated species, the long evolutionary history shared with humans has led to investigations into their cognitive abilities towards humans, particularly regarding discrimination and recognition of humans. The present study investigated whether cows are capable of visual discrimination and cross-modal recognition of familiar and unfamiliar humans. Thirty-two cows were exposed to two tests: a visual preference test, during which two silent videos were shown simultaneously - each displaying either a familiar or an unfamiliar human face - and a cross-modal test, during which the videos were accompanied by either a congruent or incongruent voice. During the visual preference test, cows looked significantly longer at the video showing the unfamiliar person (p = 0.025). In the cross-modal test, they looked significantly longer at the video that was congruent with the voice being played (p = 0.021). These two results show that cows are able to discriminate between familiar and unfamiliar individuals and form cross-modal representations of these people. Based on these results, future research should explore whether cows can adjust their behaviour depending on the person they are interacting with - a capacity that may reflect their agency in human–animal relationships.

Olfaction is the most widespread sensory modality animals use to communicate, yet much remains to be discovered about its role. While most studies focused on intraspecific interactions and reproduction, new evidence suggests chemosignals may influence interspecific interactions and emotional communication. This study explores this possibility, investigating olfactory signals in emotional contagion from the example of human-horse interactions. Cotton pads carrying human odours from fear and joy contexts, or unused pads (control odour) were applied to 43 horses’ nostrils during fear tests (suddenness and novelty tests) and human interaction tests (grooming and approach tests). Principal component analysis showed that overall, when exposed to fear-related human odours, horses exhibited significantly heightened fear responses and reduced interaction with humans compared to joy-related and control odours. More precisely, when exposed to fear-related odours, horses touched the human less in the human approach test, gazed more at the novel object, and were more startled (startle intensity and maximum heart rate) by a sudden event. These results highlight the significance of chemosignals in interspecific interactions and provides insights into questions about the impact of domestication on emotional communication.