title: Effect of calcium deficiency on survival time of young chickens acutely exposed to high temperature.
abstract: A study concerning the effect of calcium and phosphorus nutrition on the tolerance of young chickens acutely exposed to high temperature was conducted. Fasted (24 hours) chicks previously fed a low-phosphorus (LP), adequate-calcium (AC) diet exhibited reduced survival time (ST) to heat exposure when compared to chicks fed an adequate-phosphorus (AP) and AC diet. Survival time increased markedly as a result of feeding low dietary calcium. In chicks fed low-calcium diets, the level of dietary phosphorus did not influence heat tolerance. An additional experiment showed that ST of fasted chicks was inversely proportional to the level of dietary calcium fed. With respect to nonfasted chicks, diet had no effect on ST to heat exposure despite differences in plasma phosphate (Pi) and calcium (Ca). Plasma phosphate and Ca of fasted chicks were, on the other hand, not indicative of previous diet. The concentration of Ca and Pi of chicks prior to fasting was highly correlated (P less than 0.001) with subsequent heat tolerance. We suggested that the effects of diet on ST of fasted chicks may be related to nutritional alterations in Ca and Pi prior to fasting. Heat-induced changes in Ca and Pi were not related consistently to the occurrence of heat exhaustion. This suggested that changes in Ca and Pi may not be associated with heat tolerance. We concluded that previous calcium and phosphorus nutrition were dependent factors which influence markedly the survival of fasted chickens acutely exposed to high temperature.
mesh_terms: D000818:Animals; D002118:Calcium / Q000097:blood / Q000172:deficiency* / Q000494:pharmacology; D002645:Chickens / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D006359:Heat Exhaustion / Q000378:metabolism* / Q000401:mortality; D006358:Hot Temperature; D008297:Male; D010710:Phosphates / Q000097:blood / Q000494:pharmacology*
chemical_list: D010710:Phosphates; D002118:Calcium