الفهرس 
Therr." ~ "oregulat ion In SheepOnly 14 pages are availabe for public view
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Abstract
Sheep were one of the first domesticated animals,
they are able to survive under a wide range of environmen-cal
conditions, from cold LO hot dry and from sparse food to
lush green environF.ten”ts. Therefore~ rca.ny strains of sheep
we ’S evolved, ”Chose with hea;;y ·w,.oolly and dense floece,
others with light hair co<;ering, and through their adaptation
ter~, sheep developed certain features which rendered them
able to sttrvive in surrounding environments.
”L”he sub-;::rcpical zone in Eg.ypt is charactE:-rtz.-Jd by
high axb:Lent tetr.pel~at::Ul’”e, 1.nt€nsc solar radiation and lev:
rela t -=~~~-e hurr:id.i \..y ~ ’I’Lese c:or_l.di i:ons markedly affect body
L~’:’:<.:r<iTure and rt:·spira~ion rate (Hafez ~ al 1 1956).
I·c is E’S.S8l1tial in animal production to develop
a v.sll adapted breed to different localities, in which the
r”nimals r.::ach their maximum genetic productivity as a reslllt
of their rcacr ion to the external env ironmcnt:s.
\
4;ool co,:er plays an J.nportant role ”Chro~tgh insulation 1
reflection, retention, abosrption and dissipation of heat
under both hot rnd cold conditions. In recent years attention
has been focused on the role of the coat in thermal
stress. Bonsma, (19•19) and Bonsma et al , (1953 ), demonstrated
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superior growth, reproduction and prodTiction of smooch coated
as corr.pared to woolly coated beef cattle in Colonial Territeres
and has sho,.vn ttat coat type is heritable.Yeates (1954)
from studies in the psychometric cha:uber, found that ·,wolly
coa~ed cattle were at a disadvantage in the heat; a thick
curly coat constituting a th:::-eat to the ani!r;al life at 105°F.
He concluded that the heat tolerance of an ani:ual is
cl,::Jsely associated Ti’it~1 coat type; those with short
glossy coats proving superior.
flat,
The leng~L and colour of the fleece or hair of a~
aLimal affects it in rt:gt;:lat5.ng its body te:!lpera::ure a:-~d
respiration_ ::·Rte un~er tlot clir.1atic conditior:s, and t:1c
2~F.OU!1:; of hE;;J.t lc·ss frorJ t:he coat s:triace is in,:ersely
rela~ed to t~e hair ].G~g~h.
The abil.ity of sheep to maintain norr:<al rectal
temperature differ from breed to breed in the ne,;, born
and adult ones (Sykes et al, 1976 and Sloe, 1974).
Birthcoat protects the newly born lacbs from early
~ortality caused by variation in Winter weather. ~erino
lambs with a r.airy birthcoat sun·iveC: better m:der cold
conditions (Alexander 1%2 a). The Welsh j’ountain lambs
v:ich a short woolly birthcaot, are more likel~· to succumb
in severe conditions at birth than those with coarse
birthcoats (Purser and Karam, 1967).This work was carried out to study the role of
coat of both the Juvenile and adult types in thermoregulation
as well as other different means of adaptation to
the semi-arid conditions