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

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.