Factors Influencing Individual Variation in Farm Animal Cognition and How to Account for These Statistically

Abstract

For farmed species, good health and welfare is a win-win situation: both the animals and producers can benefit. In recent years, animal welfare scientists have embraced cognitive sciences to rise to the challenge of determining an animal's internal state in order to better understand its welfare needs and by extension, the needs of larger groups of animals. A wide range of cognitive tests have been developed that can be applied in farmed species to assess a range of cognitive traits. However, this has also presented challenges. Whilst it may be expected to see cognitive variation at the species level, differences in cognitive ability between and within individuals of the same species have frequently been noted but left largely unexplained. Not accounting for individual variation may result in misleading conclusions when the results are applied both at an individual level and at higher levels of scale. This has implications both for our fundamental understanding of an individual's welfare needs, but also more broadly for experimental design and the justification for sample sizes in studies using animals. We urgently need to address this issue. In this review, we will consider the latest developments on the causes of individual variation in cognitive outcomes, such as the choice of cognitive test, sex, breed, age, early life environment, rearing conditions, personality, diet, and the animal's microbiome. We discuss the impact of each of these factors specifically in relation to recent work in farmed species, and explore the future directions for cognitive research in this field, particularly in relation to experimental design and analytical techniques that allow individual variation to be accounted for appropriately.

Keel bone fractures in laying hens: a systematic review of prevalence across age, housing systems, and strains

“…However, the limitation of this approach is that flock level information may be subject to ecological bias. Ecological bias occurs when conclusions about an individual phenomenon—in this case, KBF—are drawn based on group-level data such as flock prevalence ( Siegford et al, 2016 ; Bushby et al, 2018 ). For instance, all hens in a given housing system may have access to perches but drawing the conclusion that perch use affects KBF prevalence is only valid if we can prove that the hens that used the perches are the ones who developed fractures.…”

Pre-Exposure to an Electrical Stimulus Primes Associative Pairing of Audio and Electrical Stimuli for Dairy Heifers in a Virtual Fencing Feed Attractant Trial

“…There is considerable variation between individual beef heifers [6,10] and dairy cows [14] in associative learning of audio and electrical stimuli. This variation may be associated with the specific environment and events than an individual has experienced, particularly during the developmental period [15]. For example, dairy cattle are much more likely to have experience receiving an electrical stimulus than beef cattle, through their interactions with electric fencing.…”

“…In addition to prior experiences, temperament may affect cognitive processes through its influence on emotional state, and consequently attention, memory and judgement [15,21]. For example, fearfulness (i.e., high emotional arousal to a challenging situation; Finkemeier et al [22]) is a feature of animal temperament [23][24][25] that has been associated with impaired learning in calves [26].…”

Effects of Three Distinct 2-Week Long Diet Strategies After Transport on Weaned Pigs' Short and Long-Term Welfare Markers, Behaviors, and Microbiota

“…Whereas, the potential effects of diet on behavior in pigs has been described (21), it is only in the last decade that the link between the gastrointestinal microbial population and brain function has begun to be elucidated (22,23). We now know that the microbiome and the brain communicate bi-directionally via multiple suggested mechanisms, known collectively as the microbiome-gut-brain axis (24,25). The existence of microbiome-gut-brain axis, and its relationship with behavior, affective state, cognition and stress response, is reported for numerous animal species, primarily rodents and humans.…”