Effects Of High Ambient Temperature Research Articles

Detrimental effects of high ambient temperature on fertility and early embryo survival in sheep.

Percent of ova fertilized was significantly (P<0.01)lower in ewes exposed to 32‡C temperature on the twelfth day of the cycle before breeding (40.7.% vs 94.2% for controls). The average rectal temperature of the ewes was increased 1.7‡C within 24 hr after exposure to the elevated temperature. Morphologically abnormal ova were increased from 3.8% in control ewes to 55.6% in treated ewes. In ewes exposed to the 32‡C one day after breeding all ova were cleaved,but 30.8% were morphologically abnormal. In control ewes 87.5% lambed,but none of the ewes exposed to 32‡C before or at time of breeding lambed. In ewes exposed to 32‡C at 1, 3,5 or 8 days after breeding, 20%, 35%, 40% and 70%, respectively, lambed.Embryo mortality was significantly (P<0.01) higher for all treated ewes except those in the 8-day group.The sheep zygote is most sensitive to the harmful effects of high ambient temperature during the initial stages of cleavage before it enters the uterus.

Effect of artificial fever in increasing susceptibility to bacterial endotoxin.

THERE is remarkably little information concerning the effect of fever on mechanisms of resistance to infection1. Indications of a potentiating effect of high ambient temperatures on mortality in mice challenged with endotoxin or with Gram-negative bacilli have been recorded2–4. Recently, Bannister5 has observed that high ambient temperatures potentiate the febrile response to pyrogenic doses of endotoxin in human volunteers. Burack has observed that the Shwartzman response in the skin of rabbits is also conditioned by the environmental temperature6. Work on the effect of environmental temperature on the lethality of endotoxin was therefore undertaken.

The Effect of Elevated Ambient Temperatures on the Thyroxine Secretion Rate of Chickens

EXPERIMENTAL data indicate that the thyroids of both birds (Hoffman and Shaffner, 1950) and mammals (Dempsey and Astwood, 1943) respond to a cold environment with an increase in the rate at which thyroxine is secreted. Ample evidence is also available on the effect of high ambient temperatures on thyroxine secretion rate in mammals (Pipes and Turner, 1946), however comparable data on birds are not available. Since the normal body temperature of birds is higher (7–9°F. for the chicken) than that of mammals, and since birds have no sweat glands to aid in heat dissipation, it is of interest to estimate thyroxine secretion rate as an indication of thyroid function of birds under “high” environmental temperatures. Basic information of this nature is important as a foundation for an attempt to regulate the adverse effects of high ambient temperatures during the summer months in southern parts of the country.MATERIALS AND …