- Behavioural traits are measurable characteristics describing how animals respond to people, other animals, their environment, and different situations. They are important in animal breeding because behaviour can influence animal welfare, handling safety, productivity, reproductive performance, health, adaptability, and overall management efficiency. Examples include temperament, docility, aggression, fearfulness, activity, social behaviour, maternal behaviour, grazing behaviour, feeding behaviour, exploration, and response to handling or environmental stress.
- Behaviour is influenced by both genetic and environmental factors. An animal’s observed behaviour results from interactions among its genotype, environment, physiological state, previous experience, learning, social conditions, and management. A simplified quantitative-genetics model can be represented as P=G+EP = G + E, where phenotypic behaviour is influenced by genetic effects and environmental effects. In practice, behavioural traits can also be affected by age, sex, reproductive status, health, nutrition, housing, stocking density, handling procedures, and social interactions.
- Many behavioural traits are complex quantitative traits controlled by many genes, each generally contributing a relatively small effect. Genetic variation can arise from additive genetic effects, dominance, and epistatic interactions. The additive component is particularly important in animal breeding because it contributes to differences that can be transmitted predictably from parents to offspring. The presence of additive genetic variation means that behavioural traits can potentially respond to selection, even when environmental influences are substantial.
- Temperament is one of the most commonly studied behavioural traits in livestock. It describes relatively consistent differences among animals in their reactions to handling, restraint, humans, novel situations, or stressful events. More desirable temperament can improve handling safety, reduce animal stress, facilitate routine management, and potentially improve productivity. However, the preferred temperament depends on the production system and should be defined in relation to animal welfare, safety, adaptability, and management requirements rather than simply selecting for one extreme behavioural response.
- Fearfulness and responses to humans are also important behavioural characteristics. Animals that show excessive fear during handling may experience greater stress and may be more difficult or dangerous to manage. Behavioural responses can be assessed using measures such as flight distance, movement during restraint, avoidance behaviour, novel-object tests, human-approach tests, and standardized handling scores. Because behavioural measurements can be influenced strongly by testing conditions, consistent protocols and trained observers are important for obtaining reliable phenotypic records.
- Aggression is another behavioural trait with genetic and environmental components. Aggressive behaviour may occur in response to competition, social interactions, territorial behaviour, resource limitation, or handling. In breeding programs, excessive aggression may create welfare and safety problems, while inappropriate selection against normal social behaviour could also have undesirable consequences. Behaviour should therefore be evaluated in the context of the production environment and the biological needs of the animal.
- Maternal behaviour is particularly important in species where offspring survival depends strongly on maternal care. Behaviours such as nest building, grooming, nursing, protection of offspring, and responsiveness to newborns can influence offspring survival, growth, and welfare. Maternal behaviour may interact with maternal genetic effects, milk production, litter size, birth difficulty, and environmental conditions. These relationships make behavioural traits an important part of broader reproductive and maternal breeding objectives.
- Feeding behaviour, grazing behaviour, activity, and exploration can also influence production efficiency. Individual differences in feeding patterns, time spent eating, meal frequency, grazing activity, and responses to feed availability may be associated with feed intake and feed efficiency, growth, body condition, and production. Behavioural measurements obtained from automated monitoring systems can provide large amounts of information for genetic evaluation, particularly when individual animals can be tracked continuously.
- Behavioural traits may also contribute to animal health and resilience. Animals differ in how they respond to heat, cold, social stress, handling, disease challenges, and changes in their environment. Behavioural indicators such as activity, feeding behaviour, lying behaviour, social interaction, and response to stress can provide information about an animal’s ability to cope with changing conditions. This creates potential genetic relationships between behaviour, health traits, disease resistance, survival and longevity, and resilience.
- The heritability of behavioural traits varies considerably among traits, populations, measurement methods, and production systems. Some behavioural characteristics show measurable genetic variation, while others may be strongly influenced by environmental conditions and previous experience. A low heritability estimate does not mean that a behavioural trait has no genetic importance. It means that a relatively small proportion of the observed variation in the particular population and environment is attributable to additive genetic differences. Accurate phenotyping and appropriate statistical models can improve the ability to detect genetic differences.
- Behavioural traits are often difficult to measure because behaviour can change according to context. The same animal may behave differently during routine handling, isolation, group housing, transport, feeding, reproduction, or exposure to a novel environment. Repeatability is therefore useful for evaluating whether behavioural differences remain reasonably consistent across repeated observations. Reliable behavioural phenotypes are important for estimating genetic parameters and predicting breeding values.
- Some behavioural traits are recorded as continuous measurements, such as activity level or flight distance, while others are recorded as categorical or binary outcomes, such as aggressive versus non-aggressive behaviour or calm versus excitable temperament. Appropriate statistical models are needed for different types of behavioural data. When traits are categorical or threshold-like, threshold models may be useful for separating an underlying liability from the observed category.
- Behavioural traits can be genetically correlated with economically important traits. Genetic correlations may occur between temperament and growth, feed efficiency, fertility, health, survival, production, and reproductive performance. For example, selection for production without considering behaviour could potentially produce correlated changes in behavioural characteristics. Conversely, incorporating behaviour into a balanced breeding objective can help breeders improve productivity while maintaining desirable welfare and management characteristics.
- Environmental effects are particularly important for behavioural traits. Nutrition, housing, stocking density, climate, handling, transportation, social group structure, and management practices can substantially influence observed behaviour. Genotype–environment interaction may occur when animals with different genetic backgrounds respond differently to the same environmental conditions. Therefore, behavioural breeding values may be most useful when the evaluation environment and target production system are clearly defined.
- Modern animal breeding programs can use estimated breeding values (EBVs), BLUP, and genomic selection to evaluate behavioural traits. Genomic information can increase the accuracy of breeding-value prediction, particularly for young animals that have limited individual behavioural records. Genome-wide association studies (GWAS) and quantitative trait loci (QTL) analyses can also help identify genomic regions associated with behavioural variation, although behaviour is generally influenced by many genes and complex gene–environment interactions.
- Technology is creating new opportunities for measuring behaviour on a large scale. Automated systems using cameras, accelerometers, microphones, electronic identification, activity sensors, and other precision livestock farming technologies can continuously record animal activity and behaviour. These data may provide more objective and frequent measurements than occasional human observations. However, automated measurements still require biological validation and appropriate interpretation before they can be incorporated reliably into genetic evaluations.
- Selection for behavioural traits should be part of a balanced breeding objective rather than based on a single behavioural measurement. Improving temperament or reducing undesirable behaviour can provide benefits for animal welfare, worker safety, management, and productivity, but extreme selection may produce unintended consequences. Behaviour should therefore be considered together with health, fertility, production, growth, feed efficiency, survival, longevity, and other economically and biologically important traits.
- Behavioural traits are also closely connected to animal welfare. Behaviour can provide important information about fear, stress, comfort, social functioning, motivation, and adaptation. Genetic selection may contribute to welfare improvement when it reduces excessive fear, harmful aggression, poor adaptability, or other undesirable behavioural characteristics. However, genetic improvement should complement appropriate nutrition, housing, handling, health care, and management rather than replace them.
- Behavioural genetics also contributes to understanding evolution and natural selection. Behaviour affects survival, reproduction, social interactions, resource acquisition, and adaptation to changing environments. Genetic differences in behaviour can therefore influence fitness and may change in frequency through natural selection. In managed animal populations, artificial selection can similarly change behavioural characteristics over generations.
- Overall, behavioural traits are important components of modern animal breeding because they connect genetics with animal welfare, health, productivity, reproduction, management, and adaptation. Understanding genetic variation in behaviour allows breeders to incorporate desirable behavioural characteristics into breeding objectives and selection programs. When combined with accurate phenotyping, genetic evaluation, genomic information, and balanced multi-trait selection, behavioural genetics can contribute to animals that are healthy, productive, adaptable, manageable, and well suited to their production environment.
