2. • Many studies of animal feeding show that
animals can recognize the energetic value of
foods and can take account of the energetic cost
of obtaining food when organizing their feeding
behaviour so it is clear that they have an appetite
for energy.
• This does not mean that energy intake is always
paramount in determining how feeding will
occur, however.
• Nutrient quality, other functional systems
including water balance, predator avoidance and
social factors also influence feeding.
• The termination of feeding can occur because
ingested food releases hormones
3. • The energy intake is reduced, however, if
energy intake has been higher than normal.
• Domestic animals require a variety of nutrients,
often obtained from different sorts of food.
• Taste has an effect on food selection.
• There are no regulatory ingestive systems for
specific deficiencies of minerals or essential
organic substances, but animals can learn that
certain foods reduce illness.
• Animals can compensate for deficiencies and
provide for special needs.
4. • The absence of most nutrients in the diet of farm
animals is not recognized directly, and the animals
must use trial and error learning to attempt to
compensate for dietary deficiencies.
• Mineral deficiencies can lead to pica, the seeking
out and eating of objects and materials that are
not normally food; for example, the chewing of
wood, bones, soil, etc.
• Pica is a notable feature of phosphorus (P)
deficiency in cattle. Even when given free access to
bonemeal, deficient animals still do not change the
pica to selective ingestion of the appropriate
foodstuff.
5. • When P-deficient cattle can eat such
bonemeal they seldom eat enough to correct
completely a deficiency great enough to have
caused the pica.
• Horses have been found incapable of
correcting mineral deficiency when given free
access to a digestible mixture rich in the
necessary mineral.
• In obtaining food, animals not only have to
obtain sufficient energy and nutrients but they
have to contend with the defences of the food
animals and plants.
6. • Animals deal with poisons by recognizing that a
poison has been ingested and getting rid of it
from the gut, developing enzyme detoxification
mechanisms or by learning to avoid consuming
an amount that poisons them.
• If new foods are eaten it is important to the
majority of animal species to be able to deal
with poisons.
• The simplest method for avoiding poisons is to
avoid eating any new food
7. • The desirable behavioural characteristics are:
• (i) consume only small quantities of new food;
• (ii) have a good memory for different food
characteristics;
• (iii) be able to seek out special foods;
• (iv) sample foods while eating staple foods;
• (v) prefer familiar foods;
• (vi) prefer foods with small amounts of toxic
compounds;
• (vii) have a searching strategy that compromises
between maximizing variety and maximising
intake.
8. • Given the opportunity, all grazers are selective
in their diet, but this selection depends upon
net energy return from each plant species as
well as on any toxic substances that might be
present.
• Preferences for particular plants over other
occur both when food is plentiful and when
herbage availability is low.
• The senses used in selection of plants from
pasture are sight, touch on the lips, taste and
smell but sight seems to be the least important
sense, in this respect
9. The Effects of Disturbance
• The times of starting and stopping feeding and
the rate of feeding can be considerably affected
by climatic conditions, predators, insects and
competitors.
• Animals may refrain from eating during the
hottest part of the day because they must seek
shade at this time or may cease eating during
heavy rain or high wind because the normal
feeding movements are difficult in these
conditions
10. • If an animal detects the presence of a predator
it will stop feeding, and all domestic animals
maintain some vigilance for potential
predators.
• A chicken or a sheep that spends much of its
time looking out for possible predator attack
may be unable to consume an adequate
amount of food and may feed in a different
way when it does feed.
• Insect attack may have very large effects on
feeding behaviour.
11. Social Facilitation
• Many domestic animals are species that live in
social groups, and members of a pack of dogs
or a flock of sheep are often observed to eat at
the same time as other group members.
• If cattle, sheep or pigs are taken from their
group and housed individually they eat less.
• This could be a response to lack of companions
in general or to lack of companions at feeding
time. Even when food is continually available,
social animals usually synchronize their feeding
12. • chickens in cages synchronized their feeding much
more often than would be expected by chance.
• As a consequence of such effects, the duration of
grazing is much more constant when animals graze
in a herd than when they graze individually.
• This is part of the general phenomenon of social
facilitation.
• Social facilitation is behaviour by an individual that
is initiated or increased in rate or frequency by the
presence of another individual carrying out that
behaviour.
• This is a more specific definition than the mere
social enhancement of a behaviour in the presence
of other individuals
13. • The rate of feeding is also affected by the
presence of one or more companions.
14. Competition and Feeding Behaviour
• Individuals competing for food may be
successful because of their fighting ability, or
because of threats that provide some
information about their fighting ability.
• This is not the only ability that might lead to
success, however, for competition for a food
item is often resolved by the faster-moving
individual acquiring it.
15. • If a limited amount of food is available, the
faster eater often obtains more than slower
eaters.
• Even at pasture, animals graze at faster rates
when they know that the herbage available is
limited.
• In wild ungulates, high levels of competition
for a particular food resource often lead to
individuals moving to another source in the
same area or to a new area but farm animals
often cannot do this.
16. • Unable to feed at one time should be avoided
whenever possible.
• Feeding troughs should also be designed to
minimize any fighting or threats at the time of
communal feeding.
• Feeding places with a place for each animal to
put its head are provided, there should be
enough of these places for each animal in the
group.
• More space per animal is required if no barriers
of any kind are provided.
17. Hunger, Starvation and Inability
to Obtain Food
• When an animal is not able to obtain any
food, at a time when feeding would normally
occur, the motivation to search for food
increases.
• If food is not found, further attempts to obtain
food will gradually be replaced by the changed
behaviour associated with reduced energy
availability.
18. • In a previously well-nourished individual, the
first metabolic change during a period of food
deprivation will be utilization of food reserves.
• This will be associated with the increased
presence of the metabolites of the food
reserves in the blood.
• Once the readily available food reserves have
been used up by the food-deprived animal,
other body tissues such as muscle will be
broken down, in order to provide the energy
required for survival
19. • An animal making great efforts to conserve
energy because of food deficit or to obtain food
is said to be hungry.
• The more the individual tries to do either of
these, the hungrier it is considered to be.
• Hunger may change behaviour because of the
changes in motivational state, so that greater
risks are taken in attempts to obtain access to a
feeding place, or prey in the case of predators.
20. • During a period of food deprivation, when does
starvation start?
• A useful threshold point is that starvation starts
when the animal starts to metabolize tissues
that are not food reserves, but are functional
tissues.
• If the animal starts to metabolize muscle that is
needed for effective body functioning, the
welfare is poor because there is less ability to
cope with the environment.
21. • Neglect in providing food for domestic animals, or
deliberate provision of no food or of too little food,
can also lead to hunger and subsequently, perhaps,
starvation.
• The most widely used method of detecting hunger is
to assess the level of motivation to obtain and ingest
food. One method of recognizing starvation is to
assess body condition.
• If the individual has no areas of fat, muscles are
reduced in size and bones such as the ribcage very
readily seen, it is clear that starvation has occurred.
• Early recognition of starvation involves detecting the
metabolites of muscle and other tissue breakdown.
22. Cattle
• Cattle have to rely for food intake on the high
mobility of the tongue, which is used to encircle a
patch of grass and then to draw it into the mouth,
where the lower teeth and the tongue are used to
hold the bound grass while it is broken by a head
movement.
• The nature of a cow’s eating process is such that it
is virtually impossible for the animal to take pasture
plants closer than 1 cm from the ground.
• After taking a series of bites, the cow manipulates
the plant material, chewing only two or three times
before swallowing
23. • Many studies of cattle in field situations show that
they graze mostly during the hours of daylight and
cover, on average, about 4 km/day.
• The distance travelled increases if the weather is
hot or wet or if there is an abundance of flies
around.
• During the season of hot weather, more grazing
may be done at night than during the day.
• The time cattle spend grazing during the 24 h
period is 4–14 h.
• The number of drinks taken per day is between one
and four, and the time spent lying down is usually
in the 9–12 h range.
24. • Cattle prefer to lie down during rumination
except in bad weather.
• Rumination starts in young calves of 4–6 weeks
of age after they have eaten solid, fibrous food
such as pasture plants.
• The duration of rumination increases with the
amount of solid – especially fibrous – food eaten.
• During the 24 h cycle rumination takes place
about 15–20 times, but the duration of each
period may last only a few minutes or it may
continue up to 1 h or more.
• The time spent ruminating amounts, on average,
to three-quarters of the time spent grazing.
25. Sheep
• Grazing activity by sheep is largely confined to
the daytime, and the onset of grazing is
closely correlated with sunrise.
• Grazing is punctuated by ruminating, resting
and other activities.
• The number of grazing periods over each 24 h
cycle averages four to seven and the total
grazing time usually amounts to about 10 h.
26. • The number of rumination periods may amount
to 15 during the 24 h cycle.
• Although the total time of rumination may be
from 8 to 10 h, the length of each period varies
from 1 min up to 2 h.
• Where 3–6 l of water are consumed, the number
of urinations and defaecations total
approximately nine to 13 and six to eight,
respectively. It
27. Poultry
• Pecking and swallowing is the main, minor ingestive
behaviour of the fowl.
• Free-range poultry, when they grasp a large food
object in the bill, may run with it while calling.
• Again on free range, the domestic hen typically
makes two or three backward scratching
movements with alternate feet before stepping
back one pace to peck at the area of ground that
has just been disturbed.
• Poultry typically peck at their food with jerky head
movements directed like small hammer blows.
28. • Laying birds tend to eat more at the end of the
day than non-layers, and non-layers more in
the morning.
• Reproductive state appears to be the most
important single factor causing variation in
feeding patterns.
• The type of feeding pattern shown depends
mainly on how much is stored in the crop at
the end of the day and how hungry birds are in
the morning.
29. • With non-laying birds, an increase in feeding at
the end of the day depends on an ability to
predict the onset of darkness, but with laying
birds it can also be a direct consequence of the
timing of oviposition or egg formation.
• Poultry drink frequently each day, and some
studies have shown that fowl will visit a
drinking fountain in their pen 30–40 times per
day.
• As birds get older and, usually, crowding
increases, fewer, longer-volume drinks are
taken.
