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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]

BACKGROUND Betaine and conjugated linoleic acid ( CLA) may alter growth and body composition in pigs, although their mode of action is not well understood. Portal-drained viscera ( PDV) have a disproportionate influence with respect to their masses, and this may affect the productivity of more profitable tissues. The objective of this study was to determine if the use of betaine and/or CLA in the diet affects PDV heat production. RESULTS Postprandial portal blood flow ( PBF) was greater (19.0%, P = 0.004) for control compared with the other three diets. The lowest ( P < 0.001) value for postprandial PDV O2 consumption corresponded to betaine + CLA followed by betaine and CLA diets (32.7, 25.4 and 17.7% respectively with respect to control diet). Postprandial PDV heat production was greater (26.4%, P < 0.001) for control with respect to the other three diets, with the minimum value corresponding to betaine + CLA (34.1% lower than control). CONCLUSION Supplementation with betaine and/or CLA reduced the PBF, O2 consumption and therefore PDV heat production with respect to control diet. This effect was more pronounced when betaine and CLA were supplemented together, potentially increasing the energy availability for other body tissues. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND In terms of whole-body metabolism, visceral tissues have a disproportionate influence with respect to their masses, and under certain circumstances their high metabolic rate may compromise nutrient availability to the tissues of productive/economic interest. The low energy efficiency of Iberian compared to modern breeds could be partly explained by the contribution of portal-drained viscera to heat production. The objective of this study was to determine the relative contribution of portal-drained viscera heat production ( PDVHP) to total heat production ( THP) in Iberian and Landrace gilts fed a diet with low protein content. RESULTS Compared to Landrace, Iberian gilts (29 ± 0.9 kg body weight) had lower pre- and postprandial portal vein blood flow (654 vs. 965, and 746 vs. 1133 mL min−1, respectively; P < 0.01), postprandial PDVHP (3.09 vs. 3.88 kJ h−1 kg−0.75; P < 0.01) and PDVHP/ THP ratio (0.08 vs. 0.13; P < 0.05), and greater THP (38.5 vs. 31.8 kJ h−1 kg−0.75; P < 0.05), when offered 0.25 of their daily ration in a 6 h sampling period. CONCLUSION In spite of the low energetic efficiency and growth rate of Iberian compared to modern breeds, the contribution of PDV energy expenditure relative to THP was lower in Iberian compared to Landrace gilts in the present study. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]