Control of feed and water intake in poultry

Control of Feed and Water Intake in Poultry

Plan of Talk

Control of food intake – Appetite control– Feeding rhythms – Factors determining appetite

Control of water intake

Plan of Talk



Nervous Control

1. Ascending signals are originated from:– The food itself such as color, shape and smell.– The intestinal tract following ingestion of food via receptor cells

sensitive to such parameters as taste, osmotic pressure, mechanical pressure and some metabolites.

2. These signals are transmitted to the hypothalamus. 3. Descending signals arise from the hypothalamus to transmit

information to digestive system organs as gizzard, liver, intestine and pancreas.

Appetite Control

There are many different mechanisms which are implicated in the control of appetite;1. Feeds shape2. Feed smell3. Feed color4. Feed taste5. Physical signals6. Metabolic signals7. Osmotic pressure

1- Feed Shape

Birds are sensitive to feed shape. Once they have become used to one particular form of

presentation of food, a certain amount of adaptation is necessary if another is provided. – A bird fed on pellets will need a few days acclimatization before being

able to eat the same quantity of food if it is changed to meal or whole grains.

2- Feed Smell

Birds are less sensitive to smell, or at least less than mammals.

Some experiments demonstrated that birds are able to discriminate between feeds they prefer, and those they do not, through the odor.

This phenomenon could explain certain instances of inappetance and could be used in experiments in the detection of anti-nutritional factors.

3- Feed Color

Color seems to have little influence in birds.

4- Feed Taste

Amongst ascending signals originating from the intestinal tract, the initial one is based on feed taste.

Generally, birds are less sensitive than mammals to those substances capable of increasing (sugar, aromas) or, on the other hand, decreasing (bitter) intake.

One of the best known examples is that of rape seed meal, where the bitterness will have a far greater effect with pigs, cattle and rodents than with birds.

5- Physical Signals

There are number of receptors allocated within the crop and, to a lesser extent, the remainder of the intestinal tract.

These receptors are sensitive to the physical pressure to which they are subjected.

Once stimulated, messages sent to the brain are integrated into the signal for satiety.

6- Metabolic Signal

In addition to physical signals, some metabolic signals are also present.

The best known metabolic signal is glucose, which has given rise to the glucostatic theory of appetite; 1. Hypoglycaemia stimulates a nervous centre for intake (hunger)2. Hyperglycaemia stimulates a centre for satiety. – These centers are located in the hypothalamus.

Cont. …

Some metabolites also have a role, including:1. Amino acids 2. Non-esterified fatty acids

These metabolites role seems to be less important than that of glucose.

Deficiency of some amino acids, particularly tryptophan, has a major effect on appetite by limiting food intake.

Similar responses are obtained with some excessive imbalances.

7- Osmotic Pressure

Infusion of solutions with high concentrations of potassium chloride or sorbitol into the crop or the duodenum slows down the rate of food intake.

Plan of Talk



Feeding Rhythms

Domestic birds consume their food regularly throughout the day, they do not eat discrete meals.

This behavior is related to lightening, although birds may be able to consume modest amounts under dim conditions.

Slight increase in feed intake is recorded at the beginning and the end of the light period.

Under continuous lighting conditions, the pattern of intake is constant whatever the time.

Cont. …

In laying hens, a peak in feed consumption is observed at the end of the day which is particularly pronounced if the hen is in the phase of calcification of the egg to be laid the following day.

In practice it is essential that calcium is supplied separately at the end of the day or, in the case of restriction, the compound diet is offered at the end of the day.

Plan of Talk



Factors Determining Appetite

1. Energy; feed concentration and bird requirements2. Bulk of the diet3. Protein Concentration in Feed4. Minerals 5. Vitamins6. Feed particle size

1- EnergyConcentration : Requirements

Appetite of birds is closely linked to their energy requirements. – This is explained by the fundamental role played by metabolic signals,

for example hypo and hyperglycaemia. Birds attempt to consume quantity of food necessary to meet

their energy requirements. Factors that will increase or decrease energy balance will

definitely increase or decrease appetite.

Cont. …

As a consequence, one of the characteristics of the diet which has the greatest effect on intake is its energy concentration. – A diet low in metabolizable energy will therefore increase

consumption. – The reverse is seen when energy concentration is high.

Cont. …

This homeostatic mechanism of consumption is rarely perfect; – Laying hens can adjust their energy consumption as a consequence of

dietary energy concentration. – Broiler breeders are unable to reduce their intake adequately when

dietary energy concentration increases. There are other dietary factors which have a role;

– In the species Gallus, it is the smaller birds that are most capable of maintaining energy intake constant with fairly large variations in dietary energy concentration.

– On the other hand, heavy genotypes tend to maintain intake constant irrespective of dietary energy concentration.

2- Bulk of the Diet

The physical presentation of feed and its effect inside the gastro-intestinal tract has a significant.– The presence of large amounts of plant cell wall constituents within

the feed explains the effect of bulk on the limitation to intake. – On the other hand, feed presentation in the form of pellets will reduce

this effect and allow a more accurate adjustment to energy consumption.

3- Protein Concentration in Feed

The concentration of protein in the feed has a little effect on intake.

In this context, it is essential to distinguish between:1. Productive birds (laying hens, young growing birds) 2. Adults at maintenance. 3. Growing birds

Cont. …

Productive birds Any change in dietary protein concentration might alter the

level of production and, as a result, change energy requirements, and therefore intake.

Cont. …

Adults at maintenance Concentration of dietary protein has no effect on appetite

even if it approaches zero. High levels of protein can lead to inappetance. This effect may be explained by the saturation of the

mechanisms of degradation of amino acids which result in excessive levels of uric acid.

Cont. …

When offered a choice between feed with different levels of protein that are very low or very high, most birds prefer the very low even if it is protein free.

Certain amino acids imbalances (deficiencies or excess) may influence appetite

Cont. …

Growing birds When energy requirements are met, an excess of dietary

protein will result in a moderate reduction intake without altering growth rate.

4- Minerals

Minerals may also influence appetite. Deficiencies as well as excesses of sodium, chloride and

calcium will reduce intake significantly. Between these two situations, these minerals do not seem to

have any effect. Deficiencies in trace minerals will not affect appetite unless

they are prolonged.

5- Vitamins

Growing birds Most vitamin deficiencies will reduce feed intake.

Adult birds Vitamin deficiency has no effect in adults as long as other

effects of the deficiency are not apparent.

6- Feed Particle Size

Texture as well as pelleting may influence intake. If the diet is offered as a meal, consumption will diminish in

young bird when particle sizes are small. If the mean diameter is below 800 microns, this response

becomes clearly noticeable. The depressive effect is proportional to the reduction in mean

diameter of the particles; – On average each reduction of 100 microns is associated with a

decrease in intake of 4%. Finely ground feeds are poorly consumed by poultry.

Plan of Talk



Water : Feed Intake

Water restriction There are close links between drinking and food intake.

– A restriction in water provision is associated with a reduction in food intake.

Water restriction should not be used as a means of limiting food intake because of the variable response between individual birds and the risks of alterations in renal function.

Cont. …

Feed restriction Feed restriction is often associated with an increase in water

intake, after a few days of acclimatization, which may result in a deterioration in rearing conditions as wet litter. – Thus it might be necessary to limit the amount of water available if

food restriction is being considered.

Control of Water Intake

Water intake is controlled by the hypothalamus through the osmotic receptors. – These receptors are located in the anterior region of the

hypothalamus in the preoptic region. Endogenous opiates control water intake through an

inhibitory effect whilst an antagonist such as naloxone stimulates water consumption.

Serotonin and dopamine do not appear to be implicated.

Cont. …

Birds possess the specific physiological ability of re-absorbing water from urine; this travels back up the colon, which is the site of water re-absorption resulting in the precipitation of uric acid in the form of urates which are whitish particles recovered in the excreta.

Cont. …

Water consumption and feed mineral content Water consumption may be influenced by the nature of the

diet offered to birds. – High dietary concentrations of sodium or potassium are associated

with increased intake. – Diets containing 0.25% sodium will increase water consumption by

10% compared with those containing only 0.14%. – Manipulation of dietary mineral levels is therefore a practical means of

controlling litter moisture content.

Cont. …

Water Consumption and protein concentration Dietary protein levels may equally modify water intake;

– Diets with high levels of protein result in a slight increase in water intake, this may be explained by the mechanisms of excretion of uric acid via the kidney.

– Dietary increase of 1% protein is associated with an increase in water consumption of 3%.

Cont. …

Water consumption and ambient temperature Water consumption may increase by 15% in summer when

compared with winter. Ambient temperature has a significant effect on water

consumption. – This is related to the thermoregulation mechanisms in order to

dissipate latent heat. – When ambient temperature increases, thermoregulation mechanisms

are considered an important energy losses– Birds try to save these energy losses by consumption of water.

Education

Control of feed and water intake in poultry