Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: February 28, 1997
Publication Date: N/A
Interpretive Summary: Growing-finishing pigs from 2 genetic populations known as moderate- lean and high-lean were used to study the importance of elevated air temperature on ability to grow. All measurements were made within temperature and humidity controlled rooms, using a typical range of weight and age used in the swine industry. One type of feed was used for the entire experiment and it was formulated to be adequate for the high-lean growth pigs. For the heat stress rooms, the temperatures were increased until the ad-lib-fed pigs reduced the amount of feed they ate which was measured each day. The room temperatures were adjusted each day if necessary to cause pigs to eat 13% or 26% less feed than pigs raised at non-stressing temperatures. The study ended when the average weight of the pigs in any room reached market weight. The results showed that as temperature increased, the moderate-lean pigs decreased growth about the same as they reduced feed intake. However, the high-lean pigs markedly lessened growth when they reduced feed intake. In fact, the moderate-lean pigs became somewhat more efficient while the high-lean pigs became much less efficient in their growth when under elevated temperatures. The importance of the feed formulation could not be tested in this experiment and may have been part of the reason for the large difference in results for the 2 genetic populations.
Swine of two genetic composites (moderate-growth and high-lean- growth) were each subjected to three environmental temperatures: control treatment at thermoneutral (18C), with two elevated air temperature treatments to reduce ad-lib feed intake by 13 or 26%, based on control animals of each breed. The genetic composites were penned individually, three animals per chamber, and chamber temperatures were adjusted daily to obtain the desired feed intakes based on treatment averages. Feed intakes of the controls were similar between the genetic composites but the growth rate of the lean pigs was 10% greater. Growth rates of the heat-stressed moderate-growth composites were generally reduced in proportion to feed intake and there was little effect on feed conversion. However, growth rates of the high-lean-growth composites were drastically reduced by 34 and 25% for the 26 and 13% reduced feed treatments, respectively, causing much poorer feed conversion for the heat-stressed animals. Ultrasound measured backfat was similar among the three treatments for the moderate-growth pigs but backfat and intramuscular leaf fat were increased by 10 to 25% for the heat-stressed lean pigs, respectively. All animals were fed the same ration, therefore, there were apparently differences in utilization of that ration by the two genetic composites.