Purdue University Agricultural Experiment Station Lafayette, Indiana
Mimeo AS-306 August 1961
SWINE PERFORMANCE DURING A NORMAL SUMMER AS INFLUENCED BY MIST COOLING AND SUPPLEMENTAL THIAMINE
C. J. Heidenreich, J.H. Conrad and F.N. Andrews Department of Animal Science
The influence of climatic stress on the economies of swine production has been receiving increased attention in recent years. Some of the dramatic responses noted when the climatic variable of temperature per se has been studied have spurred research efforts. Research in this area may be classified into two divisions—studies concerned with controlling the environment during which time swine performance is evaluated, and research concerned with the nature of swine response and physiological adaptation to adverse temperature regimes.
Early work at Purdue in environmental research with swine was aimed at determining suitable physical methods of modifying the depressing growth effects of elevated ambient temperatures. Hence, the development and recommendation of the mist-type spray was evolved. The benefits from supplemental cooling have been demonstrated (Purdue Mimeo AS-260. 1959). However, the tolerance of swine to short-duration high temperatures has been shown to be greater than generally believed. This was demonstrated in 1960 (Purdue Mimeo AS-289) when spray cooling failed to cause increased gains. It was concluded that daily maximum temperatures up to 90°F. are not detrimental. These findings appear contradictory to those of the California workers, 1/ who report that temperatures in excess of 80°F. reduce growth rate. Animals in a natural summer environment
are subjected to considerable diurnal temperature variations, and apparently within each 24 hour cycle, adequate physiological compensation occurs to permit optimum expression of growth. In the California work, where animals are subjected to a constant elevated temperature (environmental chambers), a relatively lower temperature stress produces depressed growth response. This is apparently due to the animals continuing thermal stress during which periodic physiological compensation cannot occur. Therefore, an abnormal physiological compensation occurs which is detrimental to optimum expression of growth.
The physiological bases of appetite depression under thermal stress pose some interesting inquiries. Some research with species other than swine has indicated a possible increase in the thiamine requirement. It is known that thiamine is necessary in the carboxylase enzyme and, hence, plays a vital role in the activation of pyruvic acid prior to entry into the oxidative metabolic cycle (heat producing). The influence of elevated ambient temperature on carboxylase synthesis and/or activity remains unknown. It is possible that increased thiamine requirements are observed due to an increased carboxylase requirement.
V Heitman, H. Jr., C. F. Kelly and T. E. Bond, J. An. Sci. 17:62. 1958