This study examined the beta-adrenergic regulation of uncoupling protein (UCP) 2 and UCP3 gene expression in porcine tissues. In vitro experiments examined changes in UCP2 and UCP3 gene expression in middle (MSQ) and outer (OSQ) subcutaneous adipose tissues from crossbred neutered male pigs. Incubation of tissue slices (24 h) with 0 to 1000 nM isoproterenol increased UCP2 and UCP3 mRNA abundanc...

A total of 54 finishing barrows (initial BW = 99.8 ± 5.1 kg; PIC C22 × 337) reared in individual pens were allotted to 1 of 6 dietary treatments in a 2 × 3 factorial arrangement of treatments with 2 levels of ractopamine (0 and 7.4 mg/kg) and 3 levels of dietary energy (high: 3,537, medium: 3,369, and low: 3,317 kcal/kg of ME) to determine the effects of feeding ractopamine and various dietary ...

Two experiments with finishing pigs were conducted to evaluate the effects of fluctuating dietary CP levels and ractopamine on performance and carcass traits. In Exp. 1, a total of 408 finishing pigs (mixed sex) were assigned to 1 of 4 protein regimens. Average initial and final BW were 89 and 123 kg, respectively. Pigs on treatments 1 to 4 were fed 16, 11, 16, and 13% CP from wk 0 to 2, respec...

This study evaluated the effects of gender and feeding of ractopamine on growth performance, carcass, and meat quality characteristics of pigs reared under commercial conditions. The study was performed as a randomized complete block design (blocking factor date of start on test) with a 3 × 2 factorial arrangement of treatments: 1) gender [gilt vs. surgical castrate vs. intact males immunocastr...

Ractopamine HCl and zilpaterol HCl, b-agonists recently approved for use in feedlot cattle to improve performance traits and carcass leanness, were examined for their effects on fecal shedding of Escherichia coli O157:H7 in feedlot cattle. Fecal samples (n ~ 2,454) were obtained from four experiments (one ractopamine HCl, three zilpaterol HCl) over the course of a 3year period, either by rectal...

Ractopamine hydrochloride (RAC) has consistently led to an advantage in carcass cutting yields of finishing pigs and remains a common feed additive in US finishing pig diets. Less is known about the effect of RAC on further processing characteristics. Some researchers have reported advantages in ultimate pH of the LM in pigs fed RAC. If a greater ultimate pH was also observed in hams, the incre...

The objective was to investigate the effect of various doses and durations of ractopamine hydrochloride (RAC) on pig HCW, cutting yields, and meat quality. Late-finishing pigs (approximately 93 kg) were allotted to 12 treatments 35 d before slaughter. Treatments consisted of negative control (NEG; 13.1% CP, 0.64 TID Lys), positive control (POS; 17.8% CP, 0.94 TID Lys), and 2 RAC doses (5 and 7....

The study used a randomized complete block design (blocking factor was date of start on test) with 5 treatments: 1) physically castrated barrows (PC), 2) intact males (IM), 3) gilts (G), 4) immunologically castrated barrows (IC), and 5) immunologically castrated barrows fed ractopamine at 5 mg/kg (IC+RAC). The study used 192 pigs and was performed from the 16 wk of age (67.2 ± 2.52 kg BW) to a ...

The present experiment utilized Berkshire (n = 76), Duroc (n = 81), and high-lean commercial crossbred (n = 75) barrows and gilts with an initial BW of approximately 85.1 kg. Pigs were fed a standard commercial diet (17.6% CP, 1.02% lysine) supplemented with ractopamine hydrochloride at a level of 0 or 10 ppm for 28 d. The experiment was conducted in a randomized complete block design, with ani...

Ractopamine-HCl was approved for use in the swine industry in 1999 and is sold under the trade name Paylean®. As of 2003 ractopamine-HCl has been approved for use in cattle fed in confinement during the last 24 to 42 d of feeding before harvest and is sold under the trade name Optaflexx®. In numerous studies with swine and emerging data with cattle, when supplemented before harvest following la...