Swine Heat Stress
The purpose of this research project is to identify the effects of heat stress on swine. Heat stress is physiological distress caused by excessive temperatures usually over 80-85 degrees Fahrenheit that can result in profoundly adverse effects in swine production. The first phase of this project involves the analysis of these harmful effects on sows, gilts, and boars. Multiple journal articles will be used to establish these effects. The final phase involves demonstrating the different techniques practiced by swine producers to combat heat stress among their swine. By identifying the solutions, this research shows how heat stress can be effectively eliminated in swine. This allows for improved swine production, management, and ultimately increased profitability. INTRODUCTION
Swine heat stress is the result of over-exposure to high temperatures. Swine have nonfunctional sweat glands, which means they have very limited self-cooling mechanisms, making over-heating a very common occurrence during warm periods. Heat stress is a severe issue, which results in annual losses to the swine industry that are estimated at $299 to $316 million. (St-Pierre, et al., 2003) This research project will examine the effects of heat stress upon sows, gilts, and boars. It will also discuss how these effects can be offset by proper herd management, sound structural utilization, and modified nutrition.
Sows, gilts, and boars are all types of swine who are common victims of heat stress. Each variety of swine is affected by heat in a different manner, but they are all equally detrimental to swine production and producer profits. Effects of Heat Stress on Sows: For sows, heat stress can cause a myriad of problems, including failure to express estrous behavior, loss of pregnancy in the first 30 days, an increase in stillbirth numbers, and feed intake reduction. A common result of heat stress in sows is failure to express estrous behavior. This failure means that there are no usual signs of standing heat, which negatively effects production, because without signs of standing heat, there is no indication of when the sow should be bred. Heat stress can be damaging to sows after being bred, as well. Research indicates that there is a strong correlation between exposure to heat stress and a lower probability of embryo survival during the first 30 days of pregnancy. (Omtvedt et al., 1971) An extensive Oklahoma University research project showed that when pregnant sows were heat stressed during the last 2 weeks of pregnancy, there was a substantial rise in the numbers of stillborn pigs per sow. The number of stillbirths increased from 0.4 stillborn per sow to 5.2 during heat stress. (Thomkins et al., 1967) The effects of heat stress can also be seen after the sow has given birth through reduced sow feed intake. An intake reduction during lactation can easily cause a chain reaction. Less feed causes extreme sow weight loss, resulting in less milk production, and in turn, decreased piglet weight gain. (McGlone et al., 1988) These are all very serious heat stress consequences that are injurious to production. Effects of Heat Stress on Gilts: Gilts exposed to heat stress exhibit many of the same pregnancy issues seen in sows. They too experience loss of early pregnancy, increased stillbirths, and reduced feed intake, as a result of being heat stressed. However, they often have difficulty even reaching puberty due to hormonal changes cause by heat stress. These hormonal shifts also result in decreased fertility rates. Gilts that are artificially inseminated after being heat stressed have a much lower conception rate. (Omtvedt et al., 1971) All of these heat stress related problems result in lower swine production rates and fiscal losses to producers. Effects of Heat Stress on Boars: Heat stress in boars can cause multiple negative production effects, including death of immature sperm cells,...
Cited: McGlone, J. J., W. F. Stansbury and L. F. Tribble. 1988. “Management of lactating sows during heat stress: effects of water drip, snout coolers.” J. Animal Sci. 66: 885-891.
Omtvedt, I. T., R. E. Nelson, R. L. Edwards, D. F. Stephens and E. J. Turman. 1971. “Influence of Heat Stress during Early, Mid and Late Pregnancy...” J. Animal Sci. 32: 312-317.
St-Pierre, N. R., B. Cobanov, and G. Schnitkey. 2003. “Economic Losses from Heat Stress by US Livestock Industries.” J. Dairy Sci. 86: (E. Suppl.): E52–E77.
Stone, B. A. 1982. “Heat induced infertility of boars: the inter-relationship between depressed sperm output and fertility and an estimation of the critical temperature above which sperm output is impaired.” Animal Reproduction Sci. 4: 283-299.
Thompkins, E. C., C. J. Heidenreich, and M. Stob. 1967. “Effect of post-breeding thermal stress on embryonic mortality in swine.” J. Animal Sci. 26: 377-380.
Wettemann, R. P., M. E. Wells, and R. K. Johnson. 1979. “Reproductive Characteristics of Boars during and after Exposure to Increased Ambient Temperature.” J. Dairy Sci. 49: 1501-1505.
Whitney, Mark. 2008. “Minimizing Heat Stress in Pigs during the Summer.” University of Minnesota Extension Publication, 298-4583.
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