Effect of added zinc in diets with ractopamine hydrochloride on growth performance, carcass characteristics, and ileal mucosal inflammation mRNA expression of finishing pigs1,2

Abstract

ABSTRACT:Two experiments were conducted to determine the effects of increasing the dietary Zn content on growth performance, carcass characteristics, plasma Zn, and ileal mucosal inflammation mRNA expression of finishing pigs fed diets containing ractopamine HCl (RAC; Elanco Animal Health, Greenfield, IN). In Exp. 1, 312 pigs (327 × 1050; PIC, Hendersonville, TN; 94 kg BW) were used in a 27-d study. There were 2 pigs per pen and 26 pens per treatment. Treatments included a corn-soybean meal diet (control; 0.66% standardized ileal digestible [SID] Lys); a diet (0.92% SID Lys) with 10 mg/kg RAC; and the RAC diet plus 50, 100, or 150 mg Zn/kg from ZnO or 50 mg Zn/kg from a Zn AA complex (ZnAA; Availa-Zn; Zinpro, Eden Prairie, MN). All diets also contained 83 mg Zn/kg from ZnSO 4 in the trace mineral premix. Pigs fed the RAC diet without added Zn had increased (P < 0.05) ADG, G:F, HCW, carcass yield, and loin weight compared with pigs fed the control diet. Increasing Zn from ZnO in diets containing RAC tended to increase (linear, P = 0.067) G:F and loin weight (quadratic, P = 0.064). Pigs fed diets with 50 mg Zn/kg from ZnAA tended to have increased (P = 0.057) ADG compared with pigs fed the RAC diet. In Exp. 2, 320 pigs (327 × 1050; PIC; 98 kg BW) were used in a 35-d study. There were 2 pigs per pen and 20 pens per treatment. Treatments included a control diet (0.66% SID Lys); a diet (0.92% SID Lys) with 10 mg/ kg RAC; or the RAC diet plus 75, 150, and 225 mg Zn/ kg from ZnO or ZnAA. All diets also contained 55 mg Zn/kg from ZnSO 4 from the trace mineral premix. Pigs fed the RAC diet had increased (P < 0.05) ADG, G:F, HCW, loin depth, percentage lean, and liver weight compared with pigs fed the control diet. No Zn level or source effects or level × source interactions were observed for growth performance. A Zn level × source interaction (quadratic, P = 0.007) was observed in liver Zn concentrations. This resulted from liver Zn concentrations plateauing at 150 mg Zn/kg when ZnO was supplemented, while there was a linear increase when using ZnAA. Increasing Zn in diets containing RAC increased (linear, P < 0.05) plasma Zn on d 18 and 32. The expression of IL-1β was increased (P = 0.014) in mucosa of pigs fed the RAC diet compared with those fed the control diet. Expression of IL-1β decreased (linear, P = 0.026) in the mucosa of pigs fed increasing added Zn. In conclusion, adding Zn to diets containing RAC resulted in a trend for improved growth performance of pigs in 1 of 2 experiments. Also, additional Zn increased plasma Zn and reduced IL-1β.

Ractopamine supplementation improves leanness and carcass yield, minimally affecting pork quality in immunocastrated pigs

“…No further evidence was reported in the literature regarding liver decrease when pigs were fed with RAC. However, similar to the observations of this study, RAC supplementation has been reported to increase liver yield (Paulk et al, 2015). More studies should be conducted to elucidate this fact.…”

Use of electromyography to detect muscle exhaustion in finishing barrows fed ractopamine HCl1

“…Crome et al (1996) demonstrated that increasing the concentration of RAC in the diet resulted in a linear LEA increase and a linear decrease in first rib, 10th rib, and last lumbar backfat thicknesses. Paulk et al (2015) reported increases in HCW of 3% and a 6% increase of loin depth and a corresponding 16% decrease in backfat depth when pigs were exposed to the same RAC feeding regimen as the current study. Burnett et al (2016) showed that 10 mg/kg RAC tended to increase HCW by 3%, increased LEA by 10%, but only tended to decrease 10th and last rib backfat.…”

“…Carr et al (2005) reported that RAC-fed barrows had increases of 16% in ADG and 19% in G:F but no differences in ADFI. Using barrows and gilts raised at the same farm as the current study, Paulk et al (2015) reported RAC fed during the final 35 d of feeding increased ADG by 11%, reduced ADFI by 6%, and increased G:F by 17%. In contrast to these studies, Armstrong et al (2004) reported that RAC fed to barrows did not influence ADG or ADFI, and Stites et al (1991) showed that regardless of RAC level in the feed, ADFI was not affected.…”

Effects of dietary copper, zinc, and ractopamine hydrochloride on finishing pig growth performance, carcass characteristics, and antimicrobial susceptibility of enteric bacteria12

“…Patience et al (2011), Rambo et al (2012), and Fry et al (2013 reported that an organic source of Zn improved performance over that of Zn from an inorganic source. Most recently, Paulk et al (2015) reported where Zn from ZnO linearly improved feed efficiency in one study but Zn from inorganic and organic sources had no response in the presence of ractopamine in a second study. Conversely, when Gowanlock et al (2013) fed diets without any trace mineral supplementation for the entire finishing period or supplemented just Zn from an organic source, no significant differences in growth performance (gain, feed intake, or feed efficiency) or in carcass characteristics (HCW, back fat depth, or loin muscle area) were observed due to a lack of Zn supplementation despite the inclusion of 10 mg/ kg ractopamine for 21 d prior to marketing.…”

“…Neither Zn nor RAC adversely affected antimicrobial resistance. However, extended feeding of 125 mg/kgtal Zn with ractopamine in the diet (Paulk et al, 2015). Copper also has been shown to improve growth and feed intake of finishing pigs (Coble et al, 2014).…”