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Swanson RM, Tait RG, Galles BM, Duffy EM, Schmidt TB, Petersen JL, Yates DT. Heat stress-induced deficits in growth, metabolic efficiency, and cardiovascular function coincided with chronic systemic inflammation and hypercatecholaminemia in ractopamine-supplemented feedlot lambs. J Anim Sci 2020; 98:5840746. [PMID: 32428228 DOI: 10.1093/jas/skaa168] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Accepted: 05/13/2020] [Indexed: 01/03/2023] Open
Abstract
Heat stress hinders growth and well-being in livestock, an effect that is perhaps exacerbated by the β1 agonist ractopamine. Heat stress deficits are mediated in part by reduced feed intake, but other mechanisms involved are less understood. Our objective was to determine the direct impact of heat stress on growth and well-being in ractopamine-supplemented feedlot lambs. Commercial wethers were fed under heat stress (40 °C) for 30 d, and controls (18 °C) were pair-fed. In a 2 × 2 factorial, lambs were also given a daily gavage of 0 or 60 mg ractopamine. Growth, metabolic, cardiovascular, and stress indicators were assessed throughout the study. At necropsy, 9th to 12th rib sections (four-rib), internal organs, and feet were assessed, and sartorius muscles were collected for ex vivo glucose metabolic studies. Heat stress increased (P < 0.05) rectal temperatures and respiration rates throughout the study and reduced (P < 0.05) weight gain and feed efficiency over the first week, ultrasonic loin-eye area and loin depth near the end of the study, and four-rib weight at necropsy. Fat content of the four-rib and loin were also reduced (P < 0.05) by heat stress. Ractopamine increased (P < 0.05) loin weight and fat content and partially moderated the impact of heat stress on rectal temperature and four-rib weight. Heat stress reduced (P < 0.05) spleen weight, increased (P < 0.05) adrenal and lung weights, and was associated with hoof wall overgrowth but not organ lesions. Ractopamine did not affect any measured indicators of well-being. Heat stress reduced (P < 0.05) blood urea nitrogen and increased (P < 0.05) circulating monocytes, granulocytes, and total white blood cells as well as epinephrine, TNFα, cholesterol, and triglycerides. Cortisol and insulin were not affected. Heat stress reduced (P < 0.05) blood pressure and heart rates in all lambs and increased (P < 0.05) left ventricular wall thickness in unsupplemented but not ractopamine-supplemented lambs. No cardiac arrhythmias were observed. Muscle glucose uptake did not differ among groups, but insulin-stimulated glucose oxidation was reduced (P < 0.05) in muscle from heat-stressed lambs. These findings demonstrate that heat stress impairs growth, metabolism, and well-being even when the impact of feed intake is eliminated by pair-feeding and that systemic inflammation and hypercatecholaminemia likely contribute to these deficits. Moreover, ractopamine improved muscle growth indicators without worsening the effects of heat stress.
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Affiliation(s)
- Rebecca M Swanson
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE
| | - Richard G Tait
- Bioinformatics and Biostatistics, Neogen GeneSeek, Lincoln, NE
| | - Beth M Galles
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE
| | - Erin M Duffy
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE
| | - Ty B Schmidt
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE
| | - Jessica L Petersen
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE
| | - Dustin T Yates
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE
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Burrack RM, Duffy EM, Yates DT, Schmidt TB, Petersen JL. Whole blood transcriptome analysis in feedlot cattle after 35 days of supplementation with a β1-adrenergic agonist. J Appl Genet 2019; 61:117-121. [PMID: 31707691 DOI: 10.1007/s13353-019-00527-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 08/27/2019] [Accepted: 10/16/2019] [Indexed: 11/28/2022]
Abstract
Ractopamine HCl (RHC) is supplemented to feedlot cattle to improve feed efficiency and increase carcass weight. Supplementation of RHC clearly benefits livestock production, but it is of note that the adrenergic system through which it acts is typically associated with stress. The purpose of this study was to identify changes in the transcriptome of whole blood in RHC-supplemented feedlot cattle. We hypothesized that transcripts related to inflammatory processes would be upregulated after 35 days of dietary RHC supplementation. To test this hypothesis, RNA from whole blood collected from 16 cattle before and after supplementation with 300 mg/day of RHC was sequenced using 3' tag-seq. Eight transcripts were differentially expressed (Adjp < 0.10) between pre- and post-supplementation blood samples. Although several of these transcripts including IFI35, TYROBP, and TP53INP1 are associated with inflammation, a systemic dysregulation of inflammatory pathways was not evident. These data provide insight into the response of cattle to RHC supplementation that will direct future studies examining how the transcriptome of whole blood and other tissues responds during acute exposure to RHC and how this supplement mechanistically improves growth performance.
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Affiliation(s)
- Rachel M Burrack
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE, 68583-0908, USA
| | - Erin M Duffy
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE, 68583-0908, USA
| | - Dustin T Yates
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE, 68583-0908, USA
| | - Ty B Schmidt
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE, 68583-0908, USA
| | - Jessica L Petersen
- Department of Animal Science, University of Nebraska-Lincoln, Lincoln, NE, 68583-0908, USA.
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Lockard CL, Richards CJ, Lockard CG, Youngers M, Woolsoncroft MA, Husz TC, Wilson BK, Goad CL, Jackson TA, Step DL, Bernhard BC, Corbin MJ, Krehbiel CR. Growth, performance, and carcass characteristics of feedlot Holstein steers fed ractopamine hydrochloride. Transl Anim Sci 2019; 4:102-117. [PMID: 32704971 PMCID: PMC6994051 DOI: 10.1093/tas/txz157] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 09/30/2019] [Indexed: 11/14/2022] Open
Abstract
Growth-promoting technologies such as implants, ionophores, and β-agonists improve feedlot performance, efficiency, and carcass characteristics of cattle. The objective of this experiment was to determine the effects of dose and duration of ractopamine hydrochloride (RH) on feedlot performance and carcass characteristics when fed to Holstein steers. A randomized complete block design was used with a 3 × 3 factorial arrangement of treatments with 3 RH doses (0, 300, or 400 mg∙steer−1∙d−1) fed for 3 durations (28, 35, or 42 d). Holstein steers (n = 855; initial body weight [BW] = 448 ± 37 kg) were blocked by BW and randomly allocated to 1 of 9 pens (15 blocks; 9 dose × duration treatment combinations) approximately 72 d before harvest. Weekly pen weights, chute temperament scores, and animal mobility were determined during the RH feeding period. At harvest, carcass data were collected on all steers, and tenderness was measured on steaks from 3 or 4 randomly selected steers from each pen and slice shear force (SSF) was determined on one steak selected from each side of the carcass after aging for 14 or 21 d. For feedlot performance, carcass characteristics, and SSF, no dose × duration interactions were observed (P ≥ 0.11). With increasing RH dose, average daily gain (ADG) and gain-to-feed ratio (G:F) increased linearly (P ≤ 0.01), whereas BW gain increased linearly with RH dose and duration (P ≤ 0.01). Hot carcass weight (P = 0.02) and longissimus muscle (LM) area (P ≤ 0.01) increased linearly with increasing RH dose. The percentage of carcasses in the USDA Yield Grade 2 category increased linearly (P ≤ 0.01) and percentage of carcasses in the USDA Yield Grade 4 category tended (P = 0.08) to decrease linearly as RH dose increased. In the 14-d aged steaks, the percentage of steaks with SSF ≤ 15.3 kg decreased linearly (P ≤ 0.01), whereas the percentage of steaks with ≥20.0 kg SSF increased linearly (P ≤ 0.01) with increasing RH dose. After 21-d aging, there was a tendency (P = 0.06) for a greater percentage of steaks from steers fed RH to have SSF ≥ 20.0 kg (2% of total steaks), but no difference (P ≥ 0.12) in the percentage of steaks with SSF ≤ 19.9 kg. Final chute temperament (P ≥ 0.45) and animal mobility (P ≥ 0.67) scores were not affected by feeding RH. Increasing the dose of RH (300 or 400 mg∙steer−1∙d−1) fed for 28 to 42 d before harvest increased ADG, G:F, hot carcass weight, and LM area when fed to Holstein steers with no negative effects on behavior or mobility. The percentage of steaks classified as not tender improved when steaks were aged for 21 d from steers treated with RH.
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Affiliation(s)
- Cathy L Lockard
- Department of Animal and Food Science, Oklahoma State University, Stillwater, OK
| | - Chris J Richards
- Department of Animal and Food Science, Oklahoma State University, Stillwater, OK
| | - Caleb G Lockard
- Department of Animal and Food Science, Oklahoma State University, Stillwater, OK
| | - Maggie Youngers
- Department of Animal and Food Science, Oklahoma State University, Stillwater, OK
| | | | - Taylor C Husz
- Department of Animal and Food Science, Oklahoma State University, Stillwater, OK
| | - Blake K Wilson
- Department of Animal and Food Science, Oklahoma State University, Stillwater, OK
| | - Carla L Goad
- Department of Statistics, Oklahoma State University, Stillwater, OK
| | - Todd A Jackson
- Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK
| | - Douglas L Step
- Department of Veterinary Clinical Science, Oklahoma State University, Stillwater, OK
| | | | | | - Clint R Krehbiel
- Department of Animal and Food Science, Oklahoma State University, Stillwater, OK
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