Problems with heat distress of Laying Hens     Summarized & Presented By Ahmed Mohamed Al-Zahrani (Ph.D student) King Saud University Advisor: Prof. Mohamed Abo Haif

Animals according to their Thermoregulation Poultry is Warm blooded animals. Poultry is Narrow tolerance range.

Cause of heat death Denaturation of enzyme. Thermal inactivation of enzyme. Interdependent metabolic reaction. Inadequate oxygen supply. Membrane structure. Dehydration.

General Problems Birds not consuming enough feed. Subtel changes in the birds metabolism affect production and shell quality. High temperature and humidity are much stressful.

PERFORMANCE OF BROWN EGG LAYERS AT 18° C VS. 30° C

Relation between total feed intake and total weigh 0. 73, 0. 88,1 Relation between total feed intake and total weigh 0.73, 0.88,1.03 and 1.33 percent at two ambient temp.

FACTORS TO ACCOMMODATE THE BIRDS REACTION TO HEAT STRESS

a) Birds response to heat stress

A narrow range of temperature (19-27 C°) over which heat production is minimum. Above 27 C° birds start to use more energy to stay cool. For example: At 27 C° birds will start to dilate certain blood vessels to get more blood to the comp, wattles, feet etc. to increase cooling capacity. At higher temp. birds will start panting and wing drooping.

These activities at high temperatures mean that birds has an increase demand for energy.

ENVIRONMENTAL TEMPERATURE AND ENERGY BALANCE.

60 g egg contains 80 kcal gross energy This require 100 kcal ME of dietary Assuming 80% efficiency of utilization of this ingested energy If the bird is at 95% prod. There is a need of 95 kcal/ME/d To sustain peak egg output. & 15-25 kcal ME For daily growth of this young pullet. For a total of 115 kcal ME/d for productive purposes.

ENVIRONMENTAL TEMPERATURE AND ENERGY BALANCE.

At moderate environmental temperature Energy yield is readily obtained from the feed With intake: 270-275 kcal ME/bird/d. (adequate for production & maintenance). As feed intake declines Available energy will decline. Although maintenance energy needs are less at higher temperature The non-linear relation causes problems of energy sufficiency at around 28 C°. Above 28 C° if production & growth are to be sustained: - The birds have to use body energy reserves in order to balance energy demands. There are obvious limits to such fat reserves (especially with young pullets) & so it is unlikely that the pullet can sustain 95% egg production for too long period under these conditions. The birds has no option to reduce egg output in order to sustain energy needs for maintenance.

Feather cover: As degree of feathering ↓ ME ↑

ME INTAKE OF LAYERS WITH 60,75 OR 90% FEATHER COVER AT 10-34° C

b) Maintaining energy balance. i) Changing diet energy level b) Maintaining energy balance. i) Changing diet energy level. ii) Physical stimulating of feeding activity. iii) body fat reserves.

i) Changing diet energy level. High production in hot need a positive energy balance. Birds consume less feed as energy level ↑ to maintain energy intake. As the energy level ↑, the decline in feed intake imperfectly regulated → overconsumption of energy. As envir. temp. ↑ the diet energy level ↑.

EFFECT OF DIET ENERGY LEVEL ON METABOLIZABLE ENERGY INTAKE

Diet need to supplemented with fat to ↑ energy level. Dietary fat has the advantage of ↑: Palatability & reducing heat increment that is produced during its utilization for production.

ii) Physical stimulating of feeding activity Its good strategy to stimulate feed intake by: Feeding more time encourage feeding activity. Feeding at coolers time of the day. With artificial lights feed at midnight. Making the diet more palatable by: Provide vegetable oil. Molasses.

This can be achieved with: Diet texture can stimulate intake (crumbles or large particle size mash feed). This can be achieved with: Quality antioxidant. Feed not be allowed to “cake”. Freshness feed.

“effective temp.” can reduced with evaporative cooling. ↑ing air movement → stimulate intake.

Cooling effect of air movement (wind chill) and expected increase in feed intake of layers maintained at 30° C

iii) body fat reserves. Hot become critical for Pullet in the peak egg mass production. Heavier bird has: larger potential energy reserve. & greater the inherent feed intake. Birds of optimum weigh with a reasonable fat reserve are best suited to heat stress.

C) Protein and amino acids

Portion It will be harmful to maintain: 19 g crud protein/bird/day during heat stress. Protein utilization → ↑ heat during its metabolism.

The extra heat production will overload heat dissipation mechanisms (panting & blood circulation). So what can we do???

Amino acid The answer is: To increase the levels of essential amino acid. By amino acids we can maintain the intake of the essential nutrients without the need to catabolize excess crude protein (nitrogen).

d) Minerals and vitamins

- Birds consume at least 4.2 g/d. Minerals Ca - Birds consume at least 4.2 g/d. - Level adjust according to reduction in intake. - In extreme condition we can add: (Oyster shell or large particle limestone) Caco3 - Beneficial to add it to the diet or drinking water. Advisable to replace 30% of salt on a kg of kg basis. K Beneficial effect of increasing k level in the diet. Carful calculation is needed since higher level can be detrimental to electrolyte balance.

Better in drinking water not Premix. Vit. B Vitamins Vit. D3 Better in drinking water not Premix. Vit. B B Vit. Provide Improvement. A, D3 & E increasing their levels have advantages. Vit. C - Birds can synthesize their needs of vit. C. - prod. Impaired under heat stress. - 250 mg vit. C/kg has beneficial for layers to maintain prod. when temp. exceed 28° C.

Diet nutrient levels needed to maintain constant intake of these nutrients at varying levels of feed intake

f) Water

“Metabolism of water” need to monitor. Birds drink more water in hot environment. As adaptation layers drink at least 50% more water at 35 vs. 22° C .

Why the success was limited? Because: Since water intake ↑ at time feed intake ↓, it would be logical to provide limiting nutrients to water. Why the success was limited? Because: Change in taste. Stimulate bacterial growth in the water lines. When envi. Temp. 30-32°C: Cooling the drinking water 5 → 8°C will stimulate feed intake 10%.

Water balance of layers at 22° C or 35° C (ml/bird/day)

Daily pattern of relative water intake Daily pattern of relative water intake. lights on @ 6:30 am for 12 hrs/d

The relationship between ambient temp. and water intake or body temp The relationship between ambient temp. and water intake or body temp. of WLH in chambers for 6 hrs

g) Effect of physical diet change

Negative of diet change: Diet change under heat stress has detrimental effect. Diet change brought about by adding fat caused an immediate rise in body temp. for up to 4 d which can cause death. Positive of diet change: Stimulate energy intake.

Effect of diet change on layer performance during heat stress

Thank you for your attention