Hunger and thirst Adroaldo J. Zanella ANS 305. Introduction 4 Freedom from hunger and thirst features as the first requirement that has to be satisfied.

Hunger and thirst

Adroaldo J. Zanella

ANS 305

Introduction

Freedom from hunger and thirst features as the first requirement that has to be satisfied in animal welfare codes/laws in many parts of the world.– Extreme– Mild deprivation

Background

Extreme nutrient and water deprivation causes death.

Failure to satisfy the animal’s requirement for essential nutrients leads to illness, poor performance and death.

Background

Mild deprivation of water and nutrients has little effect on health and vigor.

Ad libitum feeding of animals may lead to increase incidence of disease and poor reproductive performance.

Hunger & feeding motivation

The state of the animal in which it is stimulate to eat – Nutritional properties of the food– Physiological state of the animal– External factors

Problems I

Animals need to be hungry or thirsty in order to eat or drink.

Aristotelian concept of ‘telos’:– “All animals desire or strive to reach

the functional end for which they were designed”.

Problems II

A) Malnourished: conditions are limiting by being inappropriately balanced in relation to the animal’s requirements

B) Undernourished: conditions are limiting by being insufficient in relation to the animal’s requirements

A & B

Conditions

Harsh environments Hot temperatures Competitive environment Lack of feeder and drinker space Inadequate drinker & feeder design

Eating behavior

Sensory cues Nutrients in the diet Hormonal factors

Feeding strategies

Decision making processes are often overlooked.– Pigs are capable of balancing their diets– Food avoidance is common in many species – Grazers will not eat in a random fashion.

• Plant chemicals

• Feces

• Nutritional contend

Feeding patterns

Cows may graze from 4-14 h day and bite rates may vary from 40-80 minute.

Periods of high ingestive intake– Shortly prior to sunrise– Mid-morning– Early afternoon– Near dusk

Feeding patterns

Horse grazing behavior is affected by– Early experience– Quality of the pasture– Social facilitation– Temperature

Feeding patterns

Eating behavior in pigs is affected by:– Social hierarchy– Food quality– Temperature– Age– Genetic background

Measurements

A) Monitor food intake, rate of eating & time spent in food-directed activity.

B) Animal’s response to operant methodologies (e.g. the animal needs to work.

C) Trade food acquisition with aversive stimulus.

Sources of malnutrition

Unintentional:– Poorly balanced diets

Intentional– Veal calves are sometimes fed on

liquid diet deficient in iron.

Sources of undernutrition

Intentional:– Quantitative restriction

• Sows & boars (60%)

• Broiler breeders (25%)

– Qualitative restriction• Sows & boars

• Ruminants

Sources of undernutrition

Unintentional– Negative energy balance (poor

grazing conditions)– Restrictions imposed by other

group members– High temperature

• Amount eaten

• Feeding pattern

Thirst

Definition: It is a subjective sensation aroused by lack of water (Rolls & Rolls, 1982)– Physiological state– Diet– Temperature– Access to water– Water quality

Water=nutrient Adjustment of body temperature. Maintenance of mineral

homeostasis. Excretion of end products of

digestion & anti nutritional factors. Achievement of satiety. Satisfaction of behavioral drives

Secondary drinking

Hunger induced Schedule-induced polydipsia

Measurement

A) Monitor water intake, rate of drinking & time spent in drinking-directed activity.

B) Animal’s response to operant methodologies (e.g. the animal needs to work.

C) Trade water acquisition with aversive stimulus.

Water restriction

Intentional– Liquid & wet feeding (pigs)– Restricted to periods (broilers &

pigs)– Premarin farms

Water restriction

Unintentional– Blocked pipes– Inadequate flow rates– Drinker design– Water quality– Social competition

Welfare problems

Sheep will walk more than 25 km (16 miles) a day foraging

Free range sows will spent over 50% of their time foraging

Welfare problems

Expression of foraging behavior Failure to meet requirements (stress) Secondary illness associated with

nutrient (including water) deprivation

Behavioral problems

Abnormal behaviors– Tail biting– Wool-stripping

Redirected behaviors– Activity levels– Exploratory behavior

Food related stereotypies– Sham-chewing