Lecture 4 in Stress and animal health

The brain

The most complex organ in the vertebrate body and the most important organ when discussing stress and welfare.

What does brain size and composition reflect?

Processing power.

Why do we use brain size as a proxy for processing power?

Because larger brains are generally associated with greater cognitive abilities.

Domestication Syndrome

A set of traits including larger size, paler coloration, reduced fearfulness, and smaller brains in domesticated animals.

What is brain size often correlated with?

Sentience(Förmågan att känna, uppfatta och att vara medveten).

Spatial learning test

A test used to assess cognition in chickens by having them learn which alley leads to a food reward.

How did stressed chickens perform in the spatial learning test?

They needed more attempts to solve it.

Direct brain measures

Techniques that provide information about how animals perceive and respond to their environment, often difficult to perform without harm.

Examples of direct brain measures

Electrodes,

postmortem brain measures,

MRI.

What varies in gene expression?

Individual responses and behaviors, such as tail biting in pigs.

Brain lateralization

The specialization of the left and right brain hemispheres for different types of behavior and information processing.

What does the left hemisphere control?

Well-established behaviors in non-stressful situations.

What does the right hemisphere control?

Responses to unexpected stimuli and emergency behaviors.

How do cows respond to novel, fear-inducing stimuli?

They use the left eye, indicating fear.

What does left-eye preference in horses indicate?

Reactivity and coping style/personality.

What affects functional lateralization in chick embryos?

Light exposure during incubation.

Brain regression hypothesis

Suggests domesticated animals reduce brain size to reallocate energy to reproduction due to reduced functional needs.

Are brain size and body size genetically constrained in chickens?

No, they are controlled by separate genomic regions.

Cerebellum

The most neuron-dense brain region, involved in voluntary tasks and cognitive processing.

Are chickens smart?

Yes, they show mathematical ability, memory, logic, self-control, and complex social behavior.