Nutritional strategies to alleviate the effect of heat stress on Iberian pigs

High ambient temperature exposure can cause important consequences on animals’ health and production. As pigs have unfunctional sweat glands, they are more sensible to heat stress than other animals. For this reason, this experiment was held in order to study a nutritional strategy to alleviate the effect of heat stress in pigs. The nutritional strategy was to replace 5 per cent of starch by 5 per cent of high oleic sunflower oil in the diet as fat is an important source of energy and lead to a lesser heat increment than carbohydrates and protein. Therefore, a total of seventy-two castrated males crossed (50 per cent Iberian – 50 per cent Duroc) Iberian pigs weighing an average of 51.1 plus minus 0.75 Kg were exposed to high ambient temperature of (30 – 32 degrees C) during 5 hours of the day and during the other hours, the temperature was maintained at a minimum of 25 degrees C. The pigs were distributed in three rooms at the rate of four pens per room and six animals per pen. Two treatments were applied based in two different diet composition: control diet (control) and high fat diet (alternative). In addition, two forms of feeding were used. Half of the animals were fed ad-libitum and the other half restricted. Samples for the analysis of hemogram and biochemical were taken at the beginning and at the end of the study and an analysis of meat and carcass quality was performed after slaughter. Moreover, performance (feed intake, body weight) was regularly assessed and pigs’ behavior observed daily. During the experimental period, the feed intake was reduced while there was no difference on the average daily gain, consequently feed conversion ratio was lower in the alternative diet (high fat content) than in the control diet. LDL levels, the bad cholesterol, did not show any difference between the two diets showing that increasing the diet content in fat did not show bad consequences on serum lipid content in pigs. Additionally, feeding the alternative diet resulted in a higher dressing percentage and oleic content in fat. Moreover, the lying and excreting behavior in addition to the social interactions were affected by the temperature and differed between treatments. In conclusion, replacing the starch by fat during high ambient temperature conditions improved the feed efficiency, carcass characteristics and the final product obtained was more attractive to the consumers due to the higher content in oleic acid.