MANUAL AND THERMAL INDUCED FEED INTAKE RESTRICTION ON FINISHING BARROWS. II: EFFECTS ON HEAT PRODUCTION, ACTIVITY, AND ORGAN WEIGHTS

Abstract

A study was designed to investigate the bioenergetic differences in two types of feeding restriction in order toevaluate the additional effects of heat stress beyond a reduction in feed intake. Sixty Large White Landrace barrows(65.2 0.5 kg) were randomly assigned to one of five treatments: control, two levels of heat stress (HS) imposed feedingrestriction (13% HS, 26% HS), and two levels of manual feed restriction at thermoneutral (13% TN, 26% TN). Threemeasurements of heat production and activity (standing, lying, eating) were made during the trial. The pigs wereslaughtered at an average treatment weight of 107.5 kg. All organs were collected and weighed. Heat production (P <0.0001) and activity (P < 0.05) were significantly different for the different treatments. The thermoneutral treatments(control, 13% TN, and 26% TN) had the highest heat production values. These treatment groups also spent significantlyless time lying than the heat stress treatment groups (P < 0.05). The 13% TN and 26% TN pigs tended to spend more timestanding (P < 0.10) than the respective HS treatments. Although individual organ weights differed among treatment, totalmetabolically active organ weights were similar between types of restriction, indicating similar maintenancerequirements. It was concluded that activity accounted for most of the difference between the 13% HS and 13% TNgroups, while activity and composition accounted for the difference between the 26% HS and 26% TN groups.