Heat Production of Iberian Pig Exposed to High Temperature and Effect of Dietary Supplementation with Betaine or Zinc.

Simple Summary: As pigs are sensitive to heat, high temperature produces large economic losses in pig production. The Iberian pig (Sus mediterraneus) is a rustic breed that thrives in the Mediterranean forest in the southwest of the Iberian Peninsula, with hot summers, with a peak in July (32–36 °C) being more frequent due to the appearance of heatwaves in the Mediterranean area. It is well known that betaine and zinc are growth promoters in pigs under thermoneutral conditions. Betaine acts as an osmolyte, decreasing basal heat production, and zinc is very important as an enzymatic cofactor and structural element for proteins, and improves intestinal functionality. Whether betaine and zinc may mitigate heat stress in pigs remains unclear. Our aim was to study the effect of heat, and the dietary supplementation of betaine or zinc on the heat production of Iberian pigs. At 30 °C, betaine or zinc supplementation had no effect on heat production; in addition, these parameters were not affected by temperature, indicating that Iberian pigs are well adapted to hot environments. However, the ratio of CO2 production/O2 consumption indicated that supplementation with betaine may have a positive effect on lipogenesis and, thereafter, overall growth. The effect of heat, and dietary betaine or zinc on the heat production (HP) of Iberian pigs was studied. Thirty barrows (44 kg) were individually housed for 28 days and assigned to one of five treatments: (1) thermoneutrality (20 °C) and fed a control diet (TN-CON) ad libitum; (2) hot (30 °C) and fed a control diet (HT-CON) ad libitum; (3) thermoneutrality and pair fed a control diet (TN-CON-PF) to HT-CON; (4) hot and fed a betaine-supplemented (0.5%) diet (HT-BET) ad libitum; and (5) hot and fed a zinc-supplemented (0.012%) diet (HT-ZN) ad libitum. On the 18th day, pigs were moved to a respirometry chamber (two chambers) under their respective treatment. The metabolizable energy (ME) intake, HP and respiratory quotient (RQ) were measured over 24 h. No differences (p > 0.05) were found in HP and RE between treatments. For RQ, TN-CON was greater (p < 0.01) than HT treatments, except for HT-BET. All RQs indicated an overall lipogenesis where betaine supplementation showed an intermediate value, indicating that it may have a positive effect on lipogenesis and overall growth. At 30 °C, betaine or zinc had no effect on HP and RE; ME intake was not reduced, indicating a genetic adaptation of Iberian pigs to heat. [ABSTRACT FROM AUTHOR]