Page 10 - Vol.38-7 issue

ANIMAL HEALTH

UNDERESTIMATED HAZARDS OF HEAT STRESS

ON ANIMAL PRODUCTION AND REPRODUCTION

Prof. Dr. med.vet. Amr A. El-Sayed
PhD and Post Doc. J.L.U., Germany
Project Management Professional, TU-Kaiserslautern, Germany
Prof. of Internal Medicine and Animal Infectious Diseases, Cairo University.
R&D Department of Life Circle Nutrition & The Technical Sales Manager for MENA Region.

The term heat stress is being more and As high producing animals have high-
more in use during the last decades. Heat er metabolic activity than low yield an-
stress usually results from a combination of imals, they are usually more sensitive to
several climatic factors mainly the ambi- heat stress. They start to express signs
ent temperature, humidity, wind speed and of stress when the temperature exceeds
solar radiation. Although the effect of heat 20 ºC to 25 ºC depending on the species
stress on animal production is well known, and breed. The global annual losses in dairy
it is usually underestimated although the sector alone are expected to range from
decrease in milk production and feed intake $14.89 to $39·94 billion by the end of
of dairy cows due to heat stress may reach the 21th century .
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27% and 30%, respectively . In poultry Among the present strategies to deal
sector, heat stress results in adverse effects with heat stress in farm animals is the degree of surrounding temperature. For
on egg production, egg weight and shell increase of water supply and keeping long time, it was debated whether the
quality of laying hen, and increases the valuable animals/birds in air conditioned reduction of animal production is attrib-
mortalities in the flocks. The losses in egg / well ventilated houses. However, these uted to the reduction of feed intake in hot
production can reach 36%. Moreover, the two approaches face increasing costs in the days (to reduce metabolic energy) or it has
reduction in egg weight, shell weight and last few years due to the increasing energy multifactorial reasons . If the reduction in
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shell thickness may reach 17%, 37,5%, and prices and scanty of rains / dryness of many productivity is only attributed to reduction
18,7%, respectively. Meanwhile, the feed rivers around the globe in the last summer. of feed intake, the problem can be simply
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intake can be reduced by 52% . Changes in managemental and feeding po- solved by the addition of appetizers and
In the last few years, new temperature lices can also help to decrease the effects of stomachics to the feed. To answer this
records were reported in several countries. question, Life Circle Nutrition AG carried
The extreme hot summer days leads to out a simple experiment in one of our in-
changes in animal behaviour and has a neg- ternational research collaborator units (data
ative impact on both animal welfare and under publication). A group of dairy cows
productivity, immunity, and reproductive was divided into two subgroups. One was
performance. It also increases the risk of kept in their pens as usual, while the second
mastitis and endometritis, claw affections group was kept in air-conditioned pens. The
and even death specially when accompa- first group showed a clear reduction in the
nied with high humidity. The death of cows volume of produced milk and in the feed
usually occurs due to gastrointestinal tract intake, compared to the second group. The
hyperpermeability, sever electrolyte dy- volume of both the reduced feed intake
shomeostasis, multiple organ and circula- (RF) and milk (RM) were reported. Later
tory failure, intravascular hypercoagulation heat stress, such as supplementation with on, the two groups were again mixed and
and immune activated inflammation . probiotics and high-quality herbal products, re-divided into two new groups. One kept
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changing the time and composition of feed, in their usual pens and the second group
improve housing conditions and decrease was kept in air-conditioned pens. However,
the density of the birds. both groups received the same amount
of feed (RF) which represents their feed
However, to develop effective approach- requirements under high temperature sit-
es to overcome the negative effects of heat uation. Although the milk production level
stress, the physiological and pathological was improved in the group kept in air-con-
changes associated with the increase in ditioned pens, nevertheless, there was a
temperature and lead to the decrease of clear difference in the volume of produced
productivity must be first clearly under- milk between both groups, which indicates
stood. In hot seasons, the reduction in feed the role of other parameters (possibly oxi-
intake ranges from 3 to 5% per additional

8 Vol. 38 No. 7