Zilpaterol Hydrochloride Supplementation Research Articles

Influences of a Supplemental Blend of Essential Oils Plus 25-Hydroxy-Vit-D3 and Zilpaterol Hydrochloride (β2 Agonist) on Growth Performance and Carcass Measures of Feedlot Lambs Finished under Conditions of High Ambient Temperature.

Forty-eight Pelibuey × Katahdin male intact lambs (25.12 ± 3.79 kg LW) were used in a 70-d growing-finishing trial. Dietary treatments consisted of total mixed corn-based diet supplemented with: (1) no feed additives (Control); (2) 150 mg of essential oils blend plus 0.10 mg of 25-hydroxy-Vit-D3/kg diet offered throughout the 70-d experimental period (EOD3); (3) Control diet fed during the first 35 days and zilpaterol hydrochloride (ZH) supplementation at 6 mg/kg diet offered during the final 35 days of the experiment (32 days with ZH with a withdrawal 3-d before harvest), and (4) basal diet supplemented with EOD3 during first 35 days finishing, and EOD3 in combination with ZH (EOD3 + ZH) during the subsequent 32-days with ZH withdrawal 3 days before harvest. The temperature-humidity index during the experiment averaged 80.4 ± 3.2. There were no treatment interactions (p > 0.20) on growth performance and carcass measures. Supplemental EOD3 did not affect (p = 0.43) dry matter intake (DMI), but increased (p < 0.01) carcass adjusted average daily gain (ADG, 9.2%), gain efficiency (GF, 6.7%), and observed vs. expected dietary net energy for maintenance (NEm, 4.8%) and for gain (NEg, 6.4%). Supplemental ZH did not affect dry matter intake (DMI, p = 0.50) but increased (p < 0.01) carcass adjusted ADG (14.5%), GF (13%) and observed vs. expected dietary NEm (9%) and NEg (11.7%). Compared to control lambs, the combination of both additives increased ADG (24.9%), GF (21.2%), and observed vs. expected dietary NEm and NEg (14.2% and 18.9%, respectively). There were no treatment interactions on carcass characteristics, visceral organ mass, or on gene expression of IGF1, IGF2 and mTOR in longissimus muscle (LM). Supplemental EOD3 increased hot carcass weight (HCW; 4.0%, p < 0.01) but did not affect other carcass measures. Supplemental EOD3 decreased (3%, p = 0.03) intestine mass weight (g intestine/kg empty body weight). Supplemental ZH increased HCW (6%, p < 0.01), dressing percentage (1.7%, p = 0.04), and LM area (9.7%, p < 0.01), and decreased kidney-pelvic-fat percentage (16.2%, p < 0.01), fat thickness (14.7%, p = 0.03), and visceral fat. Compared to controls, the combination of EOD3 with ZH increased HCW (10.2%). It is concluded that growth performance responses to supplemental EOD3 and ZH are additive. Both supplements can be fed in combination without detrimental effects on expected benefits when fed separately. In addition, ZH supplementation improves carcass traits.

Effects of Zilpaterol Hydrochloride Supplementation on Growth Performance, Carcass Characteristics and Meat Quality for Steers Differing in Breed Type.

To determine the effects of zilpaterol hydrochloride (ZH) on growth performance, carcass characteristics and meat quality for steers differing in breed type, steers with British (B; n = 76) or British × Continental (BC; n = 57) backgrounds were allocated to a randomized incomplete block design with a 2 × 2 treatment structure. Pens within each block × breed type were randomly assigned to either ZH (8.3 mg/kg of DM; fed for 20 d before slaughter, followed by a 3-day withdrawal) or control (CON; 0 mg/kg ZH). Steers were subjected to ultrasound immediately before ZH inclusion and following withdrawal to determine the influence of ZH on changes in longissimus muscle area (LMA), fat thickness and percent intramuscular fat (IMF). Carcass data were collected, and the longissimus lumborum was collected for analysis of tenderness, moisture percentage, crude fat content, collagen content, postmortem proteolysis and sensory attributes. The ZH × breed type interaction did not influence (p > 0.05) the feedlot performance, carcass or meat quality attribute traits evaluated, with the exception of moisture percentage. Responses among breed types were as expected for B vs. BC cattle types. Supplementation with ZH improved (p < 0.05) LMA and yield grade but increased Warner-Bratzler shear force.

The Effects of Different Zilpaterol Hydrochloride Feed Supplements and Extended Aging Periods on the Meat Quality of Feedlot Bulls

This study researched the effects of two commercially available zilpaterol hydrochloride (ZH) β-adrenergic agonists, denoted as ZH-A and ZH-B, on the meat quality characteristics of typical South African feedlot bulls (taurine × indicus composites), over extended aging periods of up to 120 days. The effects of ZH were studied to address concerns about the possible adverse effects of ZH on beef quality following extended aging, which typically occurs during the exportation of beef by boat. The completely randomized control study consisted of 3 homogenous experimental groups, with 3 replicates per treatment and 50 bulls per replicate = 450 animals. Treatments were a negative control (CT) with no ZH supplementation added to the basal diet or a basal diet supplemented with either zilpaterol hydrochloride A (ZH-A) or zilpaterol hydrochloride B (ZH-B), both at 105 g ZH/ton, fed from the first day of the finishing period (D0) for 30 days. Subsamples were collected from 38 random carcasses from each treatment for proximate analysis and meat quality analysis using Longissimus dorsi samples. ZH supplementation decreased meat tenderness (Warner–Bratzler shear force values (WBSF)) of bulls fed ZH-A or ZH-B, compared to those fed the CT diet (p &lt; 0.05; η2 = 0.24). The WBSF values of both ZH treatments were about 0.5–0.8 kg higher during the aging periods compared to the CT, but ZH did not affect post-mortem meat aging or meat quality characteristics differently compared to the CT. Post-mortem aging per se influenced all meat quality characteristics investigated (p &lt; 0.001; η2 &gt; 0.30), showing improvements in WBSF, a decrease in meat colour and an increase in drip and cooking losses. L*-values increased from 3 to 56 days of aging and then decreased to day 120 (p &lt; 0.001; η2 = 032). Chroma values decreased from day 3 to day 120 (p &lt; 0.001; η2 = 0.50). Hue° decreased from day 3 to day 7 and stabilized until day 120 (p &lt; 0.001; η2 = 0.40). Moisture and cooking loss (CL) increased to 56 days and then decreased to 120 days.

PSVIII-A-8 Growth and Physiological Responses to Heat Stress and Zilpaterol Hydrochloride in Angus and Brahman Steers

Abstract The response to zilpaterol hydrochloride supplementation by two breeds of beef steers under controlled heat stress conditions were evaluated for impacts on growth, carcass merit, and physiological stress indicators. In two separate studies, Brahman and Angus steers were placed in environmental chambers and housed for 21 d under 1 of 2 environmental conditions 1) heat stress (THI = 73 to 85) or thermoneutral (THI = 68). In a 2 x 2 factorial, steers also received 8.38 mg· kg-1· d-1 on 88% DM of zilpaterol hydrochloride (ZH) or soybean meal carrier only for the 21-d period. Feed intake, respiratory rate, and rectal temperatures were evaluated daily. Total weight gain was recorded and used to calculate average daily gain (ADG) and gain-to-feed ratio (G:F). Brahman steers were harvested at the market weight (489.31 ± 97.7 kg) and Angus steers on d ~22 after treatment (307.26 ± 6.23 kg). In both studies, body weight gain and ADG did not differ between environments or supplements. Brahman steers exposed to heat stress exhibited greater (P &amp;lt; 0.05) respiratory rate than thermoneutral steers, regardless of supplement. An environment x day interactions (P &amp;lt; 0.04) was observed for rectal temperature. On d 8, unsupplemented heat-stressed Brahman steers had higher (P &amp;lt; 0.05) rectal temperatures than ZH-supplemented thermoneutral steers. On d 11, ZH-supplemented heat-stressed Brahman steers had higher (P &amp;lt; 0.05) rectal temperatures than unsupplemented thermoneutral steers. Angus steers exposed to heat stress exhibited greater (P &amp;lt; 0.05) respiration rates throughout the experiment than thermoneutral steers. On d 8, unsupplemented heat-stressed Angus steers exhibited greater (P &amp;lt; 0.05) respiration rates than ZH-supplemented heat-stressed steers. On d 8 and 19, heat-stressed Angus steers exhibited greater (P &amp;lt; 0.05) rectal temperatures than thermoneutral steers. Angus steers exhibited an environment x supplement x day interaction (P &amp;lt; 0.05) for rectal temperature, with a decrease (P &amp;lt; 0.05) rectal temperature in ZH-supplemented steers. Carcass merit traits did not differ between environments in Brahman steers. Cold carcass weights were lighter (P &amp;lt; 0.05) in heat-stressed Angus steers compared with thermoneutral steers. ZH-supplemented Angus (but not Brahman) steers exhibited decreased (P &amp;lt; 0.05) respiration rates and rectal temperatures. Together these findings indicate that Brahman steers were more resistant to heat stress than Angus steers but were less efficient, with ~10% less G:F. Based upon the data collected, supplementation with zilpaterol hydrochloride did not negatively impact production in either breed.

Transcriptome analyses indicate that heat stress-induced inflammation in white adipose tissue and oxidative stress in skeletal muscle is partially moderated by zilpaterol supplementation in beef cattle.

Heat stress (HS) triggers oxidative stress, systemic inflammation, and disrupts growth efficiency of livestock. β-adrenergic agonists supplemented to ruminant livestock improve growth performance, increase skeletal muscle mass, and decrease carcass fat. The objective of this study was to understand the independent and interacting effects of HS and zilpaterol hydrochloride (ZH) supplementation on the transcriptome of subcutaneous white adipose tissue and the longissimus dorsi muscle in steers. Twenty-four Red Angus-based steers were assigned to thermoneutral (TN; Temperature Humidity Index [THI] = 68) or HS (THI = 73-85) conditions and were not supplemented or supplemented with ZH (8.33mg/kg/d) for 21 d in a 2×2 factorial. Steers in the TN condition were pair-fed to the average daily feed intake of HS steers. RNA was isolated from adipose tissue and skeletal muscle samples collected via biopsy on 3, 10, and 21 d and sequenced using 3' Tag-Seq to an achieved average depth of 3.6 million reads/sample. Transcripts, mapped to ARS-UCD1.2, were quantified. Differential expression (DE) analyses were performed in DESeq2 with a significance threshold for false discovery rate of 0.05. In adipose, 4 loci (MISP3, APOL6, SLC25A4, and S100A12) were DE due to ZH on day 3, and 2 (RRAD, ALB) were DE due to the interaction of HS and ZH on day 10 (Padj < 0.05). In muscle, 40 loci (including TENM4 and OAZ1) were DE due to ZH on day 10, and 6 loci (HIF1A, LOC101903734, PDZD9, HNRNPU, MTUS1, and TMCO6) were DE due to environment on day 21 (Padj < 0.05). To explore biological pathways altered by environment, supplement, and their interaction, loci with DE (Praw < 0.05) were evaluated in Ingenuity Pathway Analysis. In adipose, 509 pathways were predicted to be altered (P < 0.01): 202 due to HS, 126 due to ZH, and 181 due to the interaction; these included inflammatory pathways predicted to be upregulated due to HS but downregulated due to the interaction of HS and ZH. In muscle, 113 pathways were predicted to be altered (P < 0.01): 23 due to HS, 66 due to ZH, and 24 due to the interaction of HS and ZH. Loci and pathway data in muscle suggest HS induced oxidative stress and that the stress response was moderated by ZH. Metabolic pathways were predicted to be altered due to HS, ZH, and their interaction in both tissues. These data provide evidence that HS and ZH interact to alter expression of genes in metabolic and immune function pathways and that ZH moderates some adverse effects of HS.

Does fat-tail docking and Zilpaterol hydrochloride (ZH) supplementation affect feedlot performance and carcass characteristics of finishing lambs?

The present study aimed to examine the implementation of either fat-tail docking and/or Zilpaterol hydrochloride (ZH) supplementation on feedlot performance, carcass characteristics and selected blood metabolites of fat-tailed Afshari lambs. In a 2 × 2 factorial design, 32 male lambs (41.0 ± 5.8 kg, 180 days of age) were allocated to two experimental groups consisting of 16 intact and 16 fat-tail docked lambs. Within each group, lambs were randomly assigned to two dietary treatment groups for 28 days as follows: G1; intact lambs with no ZH supplementation, G2; intact lambs with 10 mg ZH/day, G3; fat-tail docked with no ZH supplementation and G4; fat-tail docked with 10 mg ZH/day. ZH supplementation or fat tail docking did not change total body weight gain (P > 0.10). Dry matter intake was significantly increased by fat-tail docking (P < 0.01), but it was not affected by ZH supplementation. Fat-tail docking did not influence feed efficiency, while ZH improved feed efficiency only in intact lams with no significant effect on docked lambs (P = 0.05). ZH tended to decrease backfat thickness (P = 0.06) and tended to increase longissimus dorsi muscle depth only in intact lambs (P = 0.08). ZH supplementation, fat tail docking, or ZH × fat-tail docking interactions did not affect whole carcass weights and lengths (P > 0.10). Fat-tail docking resulted in a nearly 2-fold increase in fat thickness covering longissimus dorsi muscle in docked lambs with no ZH supplementation; however, ZH supplementation prevented this increase in longissimus dorsi muscle fat thickness (P = 0.03). In summary, fat-tail docking did not notably affect feedlot performance and carcass characteristics; however, it increased dry matter intake and subcutaneous fat thickness as well as visceral organs weights and visceral fat deposits. ZH supplementation did not influence feedlot performance but significantly improved carcass characteristics, as indicated by lower fat and higher muscle and protein content of carcass both in docked and intact lambs.

Effects of duration of zilpaterol supplementation on growth-performance, dietary energetics, carcass characteristics, and meat quality of crossbred yearling heifers slaughtered at lighter, less-than-mature final body weight (460 kg)

Our objective was to examine the effects of duration of zilpaterol hydrochloride (ZH) supplementation on growth performance, estimated dietary energetics, carcass characteristics, and meat quality in crossbred yearling heifers when slaughtered at lighter, less-mature final weight. Treatments consisted of a finishing diet based on steam-flaked corn supplemented with (1) 0 ZH (negative control); (2) 0.15 mg of ZH/kg of live weight supplemented for 20 of the final 23 d of the finishing period; (3) 0.15 mg of ZH/kg of live weight supplemented for 25 of the final 28 d of the finishing period, or (4) 0.15 mg of ZH/kg of live weight supplemented for 30 of the final 33 d of the finishing period. Duration of ZH supplementation did not affect ( P ≥ 0.15) any of the variables measured. Compared with the control, ZH increased ( P ≤ 0.02) carcass-adjusted weight gain, G:F, and apparent dietary NE. Zilpaterol supplementation also increased ( P ≤ 0.05) hot carcass weight, carcass DP, and LM area without effects on USDA QG, fat thickness, or KPH fat. Zilpaterol supplementation increased ( P < 0.01) gross retail cuts by 3.6%, when adjusting to a constant carcass weight. There were no treatment effects ( P ≥ 0.11) on shear force or meat color. Zilpaterol hydrochloride supplementation in heifers slaughtered at a final weight that was less than was estimated to be mature (460 kg) improved growth performance, hot carcass weight, carcass DP, LM area, and retail cuts in a manner consistent with results of previous studies in which heifers were slaughtered at heavier (>550 kg) BW. Effects of ZH on meat quality was not significant. Reducing ZH feeding duration from 30 to 20 d may not adversely affect growth performance, carcass characteristics, and meat quality.

Meat Quality of Nellore Young Bulls-Effects of Different Days on Feed and Zilpaterol Hydrochloride Supplementation.

Simple Summaryβ-adrenergic agonists have been widely used to improve meat production efficiency and can be a valuable tool for increasing world meat supply. They act as nutrient repartitioning agents, increasing lean tissue deposition but negatively affecting meat quality, notably reducing palatability. While this metabolic modifier improves the growth performance of Zebu breeds, they can impair even more meat quality in feedlot-finished cattle. This study was developed to evaluate the impact of zilpaterol hydrochloride (ZH) feeding duration and time on feed (90 or 117 days), on meat quality, and on composition properties of meat from young Zebu bulls. Supplementing ZH resulted in a leaner and less tender and juicy meat compared to non-supplemented animals, with few differences in fatty acid composition. Feeding animals for 90 or 117 days had a small impact on meat quality attributes. Feeding ZH to Zebu bulls would require additional tenderization practices to reduce the negative effects of ZH on meat quality.Ninety-six Nellore young bulls were fed (90 or 117 day) diets containing ZH (8.33 mg/kg) for 0, 20, 30, or 40 days to evaluate the effects of days on feed (DOF) and length of zilpaterol hydrochloride (ZH) supplementation on meat quality. At the end of feeding period, animals were slaughtered, and samples of the Longissimus muscle were collected to evaluate the chemical composition, fatty acid profile, color stability, shear force, and sensory profile. DOF did not affect chemical composition, shear force, sensory tenderness, and most of fatty acids; however, animals fed for 90 d had lower redness (p < 0.01), sustained juiciness (p < 0.01), and more flavor (p = 0.03) than those fed for 117 d. The ZH supplementation decreased lipid content and redness (p < 0.01), initial and sustained tenderness (p < 0.01), initial and sustained juiciness (p < 0.01), but increased protein (p < 0.01) and shear force (p < 0.01) as compared to non-supplemented animals. The ZH supplementation increased total PUFA, c9,c12-18:2, and 20:4-n6, and decreased c9-20:1 (p < 0.05). Feeding ZH impairs meat quality attributes of Nellore young bulls, regardless of duration of supplementation, while DOF has a small effect on meat quality properties.

Effects of the Duration of Zilpaterol Hydrochloride Supplementation and Days on Feed on Performance, Carcass Traits and Saleable Meat Yield of Nellore Bulls.

Simple SummaryZilpaterol hydrochloride (ZH) is a β-adrenergic agonist (βAA) to be feed to feedlot cattle at a rate of 8.3 mg/kg during the final 20 to 40 d of the finishing period followed by a minimum 3 d withdrawal period. This compound has the potential to increase animal performance, improve carcass weight and meat yield. Although significant information regarding the effects of duration of ZH supplementation and days on the feed of Bos taurus cattle has been provided, there is a lack of information relative to its effects on Bos indicus breeds such as Nellore cattle. The current study aimed to evaluate the effects of the duration of ZH supplementation and DOF on performance, carcass characteristics, and saleable meat yield of Nellore bulls. The HCW and total saleable meat yield linearly increased with the duration of ZH supplementation as well as when the length of the feedlot period increased. We recommend supplementing ZH for Nellore bulls at least for 20 days, independently of days on feed, to improve hot carcass weight, hindquarter, and saleable meat yields of Nellore bulls.This study evaluated the effects of the duration of ZH supplementation and days on feed (DOF) on performance, carcass characteristics, and saleable meat yield of Nellore young bulls. The fixed effects included the duration (0, 20, 30, or 40 d before slaughter plus a 3 d ZH withdrawal period—8.33 mg of ZH/kg of DM) and DOF (90 and 117 d). Feed efficiency (G:F) linearly increased when the duration of ZH supplementation increased (p < 0.01). Nellore bulls fed ZH had greater HCW (p < 0.01), dressing percentage (p < 0.01) and Longissimus muscle area (LMA) (p < 0.01), but less 12th-rib fat (p = 0.04) than the control group. The hot carcass weight (HCW) (p < 0.01), and dressing percentage increased linearly (p < 0.01) with the increase of duration of ZH supplementation. The HCW, ossification, and 12th-rib fat increased with DOF (p < 0.01). The ZH supplemented group had most of the individual cuts of hindquarters and total saleable meat increased compared with the control. Zilpaterol hydrochloride was effective in improving hot carcass weight, hindquarter, and saleable meat yields of Nellore bulls when fed for at least 20 d before slaughter, independently of days on feed.

Evaluación de dos fuentes suplementarias de clorhidrato de zilpaterol sobre la calidad de la carne y los rasgos de la canal de toros Bos indicus cruzados en los trópicos

It was studied the effect of two zilpaterol hydrochloride (ZH) brands on carcass and meat quality traits of crossbred Bos indicus young bulls under tropical conditions. The patented ZH formulation (Zilmax®, ZHp) and a generic brand (Zipamix®, ZHg) were added to the feed (6 ppm) for 30 d before slaughter. Animals (n= 288) were randomly assigned to 1 of 3 diets, with 32 animals per pen and 3 replicates, for a total of 96 bulls per treatment: 1) basal diet without ZH (Control), 2) basal diet supplemented with Zipamix® at 6 ppm in the diet, as fed-basis (ZHg), and 3) basal diet supplemented with Zilmax® at the same concentration in the feed (ZHp). Carcass yield traits were significantly improved by ZH supplementation. Carcasses of ZH-treated bulls were 6-9 kg heavier (P=0.0023) and produced about 8-10 kg more of lean tissue (P&lt;0.0001) as compared to the Control group. Carcass quality traits were less affected by ZH supplementation. Among meat quality attributes, ultimate pH of ZHg (5.81) and ZHp (5.89) was higher (P=0.0022) than that of the Control (5.78). Results showed both ZH brands, when administered for 30 d before slaughter, as recommended by the manufacturer, improve most carcass yield traits without compromising carcass or meat quality attributes. Hence, tropical beef producers may use the ZH formulation of lowest cost to improve their productivity.

131 Zilpaterol Hydrochloride and Heat Stress Each Alter the Cattle Adipose Transcriptome and Predicted to Alter Molecular Pathways After 21 Days

Abstract Heat stress reduces livestock performance while supplementation of beta-adrenergic agonists (βAA) such as zilpaterol hydrochloride (ZH) improve production efficiency; both stimulate lipolysis. The objective of this study was to understand the effects (independent, interacting) of heat stress and ZH on the subcutaneous adipose transcriptome in fed steers. 24 Red Angus steers were assigned to thermoneutral (TN; THI=68) or heat stress (HS; THI=83) conditions and fed no supplement (NS) or ZH (8.33 mg/kg/day) for 21d in a 2x2 factorial. TN steers were pair-fed the HS daily average. Subcutaneous adipose samples were collected at day -3, 3, 10, and 21. RNA was isolated and sequenced using 3’ Tag-Seq reads to a depth of 3.6 million reads/sample. Transcripts were mapped to ARS-UCD1.2 and quantified. After quality control, differential expression (DE) analyses were performed in DESeq2 with a significance threshold (FRD) of 0.05. Pathway analysis was used to explore pathways affected by HS, ZH, and their interaction using DE loci (P &amp;lt; 0.05). The acute phase response signaling pathway was predicted to be activated at 3d, but inhibited at 10d and 21d by the combination of HS and ZH. At multiple time points, inflammatory pathways including those for interferon and IL-8 were predicted to be activated by HS. Mitochondrial function pathways including oxidative phosphorylation, mitochondrial dysfunction, and TCA cycle II were altered by ZH. Adipose centric pathways for phospholipase-C and protein kinase-A signaling were altered by HS/ZH interaction while glycolysis was altered solely by HS. These data support the hypothesis that exposing cattle to HS conditions and ZH supplementation alters the subcutaneous adipose transcriptome, but not necessarily in an additive fashion. These data provide information regarding the supplementation of βAA in heat stress environments, especially if it mediates the effects of HS.

Efecto de la adición de clorhidrato de zilpaterol genérico en el perfil bioquímico y hematológico de ovinos de pelo engordados en corral

El objetivo fue evaluar la adición de clorhidrato de zilpaterol (CZ, genérico) en la dieta de ovinos de pelo de engorda, sobre variables hematológicas y bioquímicas como indicadores del estado de salud. Treinta y dos (32) corderos de pelo cruzados (Dorper x Pelibuey) se bloquearon por peso inicial y cuatro tratamientos y se asignaron aleatoriamente dentro de cada bloque: T1= dieta basal (grupo testigo), T2= dieta basal más 0.10 mg·kg-1 de PV d-1 de CZ (Grofactor®, Virbac México, Guadalajara, México), T3= dieta basal más 0.20 mg·kg-1 de PV d-1 de CZ y T4= dieta basal más 0.30 mg·kg-1 de PV d-1 de CZ. Se tomaron muestras de sangre los días 1, 15 y 30 del estudio. El perfil hematológico se estimó en muestras de sangre fresca, mientras que metabolitos, electrolitos y hormonas en muestras de suero. El diseño experimental fue bloques completos al azar y se efectuó análisis de polinomios ortogonales para determinar la tendencia de las respuestas a los niveles de CZ. Los niveles de colesterol y urea fueron mayores (P&lt;0.05) en T3 que en T2; asimismo, el nivel de concentración corpuscular medio de hemoglobina fue mayor (P&lt;0.05) en T1 que en T3, mientras que el ancho de distribución de eritrocitos fue mayor (P&lt;0.05) en T2 y T3 que en T4. Los niveles de Na y el número de plaquetas mostraron tendencia lineal (P&lt;0.05) a disminuir y aumentar, respectivamente, conforme los niveles de CZ aumentaron. Se observó tendencia cuadrática (P&lt;0.05) en la concentración corpuscular media de hemoglobina y ancho de distribución de eritrocitos al aumentar la dosis de CZ (genérico). Las variables restantes no mostraron tendencias significativas a los niveles de CZ (genérico). Los valores de los perfiles bioquímico y hematológico se encontraron dentro del rango de referencia, lo que sugiere que la adición de CZ no alteró el estado de salud de corderos en engorda.

PSI-14 Feeding β-agonists under heat stress conditions in feedlot cattle

Abstract Red Angus steers (n = 24; 260 ± 25 kg) were used to analyze the effects of supplementation of zilpaterol hydrochloride (ZH) under heat stress conditions on respiration rate (RR), rectal temperature (RT), growth performance (GP), and carcass traits (CT). Steers were randomly assigned to a 2 x 2 factorial treatment arrangement (n = 6/group) with factors including heat stress (HS; THI=71 to 83) or thermal neutral (TN; THI=27 to 39) conditions and with/without supplementation of ZH (0 or 8.38 mg/kg/d on 88% DM basis). Steers were provided 9 d to acclimate to tie stalls rooms under TN conditions before starting the study. TN steers were pair-fed to the average daily dry matter intake (DMI) of HS steers. Ad libitum water consumption (WC) was recorded daily. HS and TN steers were harvested on d 22 and 23, respectively. By design, DMI was not different between environments (P = 0.43). DMI also did not differ between supplement groups (P = 0.31). RT, RR, and WC were greater (P &amp;lt; 0.01) in HS steers compared to TN steers. There was a supplement by environment interaction (P = 0.02) for RT, as HS steers fed ZH had lower RT than HS control steers (39.1 vs 39.5 ℃). ADG was 20% higher (P = 0.04) in HS steers compared to TN steers. CT did not differ (P = &amp;gt;0.05) due to environment, treatment, or interactions between environment and ZH supplementation. Our results suggest that feedlot steers under our experimental conditions display some sensitivity to HS through GP, RR, and RT, however, this did not translate to an impact on CT. Furthermore, ZH supplementation under HS conditions appears to impact thermoregulatory responses positively, yet this did not impact GP or CT.

Effect of Zilpaterol Hydrochloride on Performance and Meat Quality in Finishing Lambs

Twenty-four Dorper x Pelibuey lambs were housed in individual pens during a 31-d feeding period and assigned to four treatments (n = 6) under a randomized complete block design with different daily doses of zilpaterol hydrochloride (ZH): 0 (control), 0.1, 0.2, and 0.3 mg/kg BW to determine the effects of ZH supplementation on productive performance, meat quality, and wholesale cut yields. Final BW (p = 0.02) and average daily gain (ADG, p = 0.04) were greater in lambs supplemented with 0.2 mg/kg BW. Supplemental ZH tended to improve dry matter intake (DMI, p = 0.008) and ADG:DMI ratio (p = 0.078). Wholesale cut yields were not affected by ZH supplementation. Percentage of head was greater (p = 0.04) in lambs treated with ZH. The ZH supplementation did not affect carcass characteristics. However, longissimus thoracis et lumborum (LTL) presented a linear trend (p = 0.08) of increasing with ZH supplementation. Percentage of blood presented a trend (p = 0.051) of decreasing with ZH supplementation. Also, liver decreased in size (p &lt; 0.05) for treatments where ZH was included. Values of luminosity decreased (p &lt; 0.02) when ZH dosage increased. The value of protein Lowry was greater, with 0.3 mg kg−1 (p = 0.04). Cathepsin B + L was greater in the lambs from the control treatment (p = 0.05). In conclusion, using a daily ZH dosage of 0.2 mg per kg of BW produced the best productive performance, carcass characteristics, and some changes in the meat of hair-breed lambs.

Welfare traits of Bos indicus cattle castrated immunologically and fed beta-adrenergic agonists.

ObjectiveThis work was carried out to evaluate the effects of zilpaterol hydrochloride (ZH) and ractopamine hydrochloride (RH) combined with immunocastration on the welfare traits of feedlot Nellore cattle.MethodsNinety-six Nellore males (average body weight [BW] = 409±50 kg; average 20 mo of age) were divided into two groups according to BW; half of the animals in each group received two doses of an immunocastration (ImC) vaccine in a 30 day interval, and the other half did not receive the vaccine (NoC). Afterward, the animals were housed and fed a common diet for 70 days. Then, they were split into three groups and fed one of the following diets for 30 additional days: control (CO) diet, with no β-AA; ZH diet, containing 80 mg/d ZH; and RH diet, containing 300 mg/d RH. Welfare traits were assessed by monitoring body surface temperature using infrared thermography (IRT) and plasma cortisol and temperament measurements.ResultsThere was no interaction between sexual condition and diet for any trait. The ImC and NoC groups did not differ in rectal and ocular temperatures. The ImC animals had higher flight speeds (p = 0.022) and tended to have higher cortisol levels (p = 0.059) than the NoC animals. Animals fed ZH and RH did not differ in cortisol levels, respiratory rate, rectal temperature, temperature measured by IRT, or temperament behaviour.ConclusionThe ImC animals showed a less stable temperament during handling practices than NoC, whereas ZH and RH supplementation had no adverse effects on animal welfare.

Feedlot performance, carcass characteristics and meat quality of Nellore bulls and steers fed Zilpaterol hydrochloride

This study aimed to determine the effects of zilpaterol hydrochloride (ZH) on feedlot performance, carcass traits, feeding behavior and meat quality characteristics of Nellore steers and bulls. This study was conducted at the São Paulo State University (UNESP) feedlot, Botucatu Campus, Brazil. Seventy-two 18-month-old Nellore cattle from the same cattle herd, 36 steers and 36 bulls, were selected for this study. The experiment had a randomized block design based on the animals’ initial BW, in a 2 × 2 factorial arrangement of treatments, in which the factors were ZH addition to the diet (0 or 7.5 mg of ZH/ kg of feed 20 d prior to slaughter; ZILMAX® MSD Animal Health, São Paulo, SP, Brazil) and gender (bulls or steers). The 24 pens were considered the experimental units in this study, and each treatment was replicated six times (n = 3 per pen). Cattle were fed for 112 days, and the addition of 7.5 mg of ZH/ kg of feed was done for 20 d prior to slaughter (from day 90 to day 109). A withdrawal period of three days before slaughter was respected (from day 110 to 112). During the period of ZH supplementation, cattle fed ZH presented greater final BW (516.45 vs. 512.50 kg; P ≤ 0.001), ADG (1.73 vs. 1.32 kg; P ≤ 0.001), and improved G:F by 38.1% (0.187 vs. 0.135; P ≤ 0.001), when compared to cattle not fed ZH. Nellore steers receiving ZH reduced DMI by 9% when compared to steers not fed ZH (P = 0.04); however, Nellore bulls had similar intake regardless of ZH supplementation. Overall, cattle receiving ZH improved G:F by 6.6% (0.161 vs. 0.151; P = 0.03) and increased final LM area (79.32 vs. 76.30 cm2; P = 0.04), HCW (292.75 vs. 280.00 kg; P < 0.001), and dressing percentage (56.68 vs. 55.14; P < 0.001). The interaction between ZH supplementation and gender was observed (P = 0.02) for 12th rib fat daily gain in which steers decreased their rate of fat deposition when fed ZH, but no effect was observed for bulls. A significant increase was observed (4743.12 vs. 4286.23 µm2; P = 0.03) in the average area of Semitendinosus muscle fibers of cattle supplemented with ZH; however, no main effect of ZH supplementation was observed for final marbling (P = 0.27) or shear force (P = 0.20). Overall, ZH increased performance and hot carcass weight of Nellore cattle regardless of gender. In addition, supplementation of ZH lead to similar feedlot performance and meat quality between Nellore steers fed ZH and Nellore bulls not consuming ZH.

Daily optimal level of a generic beta-agonist based on zilpaterol hydrochloride for feedlot hair lambs

Two experiments were completed to determine the dietary optimal dose of a generic product (Grofactor®) of zilpaterol hydrochloride (ZH) in fattening male lambs. In experiment 1, 32 lambs were assigned to four daily doses of ZH (n = 8): 0 (Control), 0.10, 0.20, and 0.30 mg/kg of body weight (BW). In experiment 2, the doses of ZH with the best biological response from experiment 1 (i.e., 0.10 and 0.20 mg/kg of BW per lamb) were compared using 18 lambs (9 lambs per treatment), as well as a control group of 9 lambs. In experiment 1, growth rate, feed efficiency, hot (HCW) and cold (CCW) carcass weight and dressing percentage showed a quadratic increase (P ≤ 0.05) as the dose of ZH increased, but all these traits were similar among ZH-fed lambs. Yield of wholesale cuts was not impacted by ZH dose. Percentages of skin and foot decreased linearly (P ≤ 0.01) with increasing ZH dose. However, head, liver, and stomach had a quadratic effect (P ≤ 0.05) to increasing levels of ZH, with the lowest values at the intermediate ZH addition levels. In experiment 2, ZH-fed lambs compared with control had better (P ≤ 0.04) feedlot performance, HCW, CCW, dressing percentage, Longissimus dorsi muscle area and carcass length. Addition of ZH only increased (P ≤ 0.03) the leg yield using any of the doses. Feeding ZH decreased (P ≤ 0.03) the percentages of blood, liver, spleen, and stomach, while percentage of lungs increased (P < 0.01). In both experiments, ZH supplementation had no effect on fat thickness, and omental and mesenteric fat. We concluded that generic ZH is effective as growth promoter in male lambs finished in feedlot to a daily dosage of 0.10 mg/kg of BW.

Carcass fabrication yields of beef steers supplemented zilpaterol hydrochloride and offered ad libitum or maintenance energy intake.

An experiment was conducted to evaluate the fabrication yields of carcasses from beef steers supplemented zilpaterol hydrochloride (ZH) and fed at maintenance (MA) or ad libitum (AB) intake levels. Beef steers (n = 56) from a common sire were blocked (n = 28 per block) by terminal growth implant and sorted into pairs by BW. Four pairs (n = 8) were harvested on day 0; the remaining 24 pairs (n = 48) were assigned to a dietary intake level (MA or AB) and days on feed (28 or 56 d). Within pairs of MA or AB intakes, steers harvested on day 56 were randomly assigned to supplementation of ZH (90 mg·d−1 per steer) for 20 d followed by a withdrawal period of 4 d or control (C). Steers (BW = 603.5 ± 48.1 kg) were harvested at a commercial processing facility. After a 24-h chill period, standard USDA grading procedures were used to derive a calculated yield grade and quality grade. Following grading, left carcass sides were transported to the West Texas A&M University Meat Laboratory for fabrication. Each side was fabricated into subprimals to determine individual red meat yield (RMY), trimmable fat yield (TFY), and bone yield (BY). A mixed model was used for analysis; fixed effects included treatment combinations and random effects included block and pairs. Single df contrasts tested day 0 vs. 28, day 0 vs. 56, day 28 vs. 56, MA vs. AB, and C vs. ZH. Yield of chuck eye roll differed (P = 0.05) by days on feed (0 d = 4.14, 28 d = 4.11, 56 d = 4.55%). Similarly, eye of round yield was impacted (P = 0.02) by days on feed (0 d = 1.51, 28 d = 1.37, 56 d = 1.36%). Additionally, brisket yield was altered (P < 0.01) by days on feed (0 d = 4.08, 28 d = 3.56, 56 d = 3.48%) and treatment (C = 3.34, ZH = 3.61%). For remaining subprimals, no differences (P ≥ 0.15) were detected. Furthermore, results indicated that RMY tended (P = 0.07) to differ by treatment (C = 61.35, ZH = 63.67%). Comparatively, TFY was impacted (P = 0.04) by intake (MA = 20.44, AB = 23.33%). Results from this study indicate that a MA intake level during the last 56 d of the finishing period concurrent with ZH supplementation impacts subprimal yields as well as carcass RMY and TFY of beef steers.

Effect of short-term beta-adrenergic agonist administration along with progestin estrus synchronization on estrous behavior, reproductive performance and ovarian structures of Rambouillet ewes

The aim of this study was to evaluate the effects of short-term supplementation of the beta-adrenergic agonist (β-AA) zilpaterol hydrochloride (ZH) along with progestin estrus synchronization on weight gain, estrous behavior, ovarian structures and reproductive performance of Rambouillet ewes. Thirty-one Rambouillet ewes (12–14 months old and 3.2 ± 0.2 body condition score in a scale of 1–5) were primed with intravaginal sponges (20 mg chronolone) for 14 days and injected with a single i.m. dose of 400 IU of eCG at sponge removal. Treatments consisted of 1) β-AA group (n = 15, ZH supplementation in diet at a dose of 0.15 mg/kg/d, from day 6 to day 2 before sponge removal), and 2) Control group (n = 16, general management without ZH supplementation). Weight gain, estrus behavior, reproductive performance and ovarian structures by transrectal ultrasonography were recorded. The number of matings per ewe and duration of standing estrus were greater (P < 0.05) in the ewes treated with β-AA (3.3 ± 0.2 matings and 37.2 ± 3.0 h, respectively) than in ewes of the Control group (1.9 ± 0.2 matings and 26.7 ± 3.1 h, respectively). In addition, the short-term treatment with β-AA reduced (P = .0269) the ovulation time after sponge removal (32.4 ± 4.1 vs. 46.5 ± 4.5 for β-AA and Control groups respectively), but increased (P = .0319) the average diameter of the CL (6.9 ± 0.5 vs. 5.6 ± 0.5 for β-AA and Control groups respectively). The short-term supplementation of β-AA to ewes along with progestin estrus synchronization, increase estrous behavior and size of the CL, without affecting pregnancy rate, prolificacy or follicular development in ewes. Results of this study contribute to a better understanding of the effect of β-adrenergic stimulation on sheep reproduction and its possible use in estrous synchronization schemes.

Live growth performance, carcass grading characteristics, and harvest yields of beef steers supplemented zilpaterol hydrochloride and offered ad libitum or maintenance energy intake.

A trial was conducted to examine live growth efficiency, harvest yields, and carcass grading performance of steers fed at maintenance (M) or at ad libitum (A) level of intake during zilpaterol hydrochloride (Z) supplementation. Single-sired, beef steers (n = 56; start of trial BW 590 ± 36 kg) blocked (n = 2) by weight and terminal implant were sorted into pairs (n = 14 per block) by weight. Pairs of steers were initially assigned to 0, 28, or 56 d of feeding. Within 28 or 56 d, pairs were assigned to M or A intake. Steers within a pair assigned to 56 d of feeding were randomly assigned to either 20 d of Z supplementation (90 mg/d per steer) with a 4 d withdrawal period prior to slaughter or to no ZH supplementation (C). Steers were housed and fed in individual pens. Weights of all non-carcass and carcass components were recorded at slaughter; carcasses were graded 24-h postmortem. Data were analyzed via a mixed model; the fixed effect was treatment combination with random effects of block and pair. Live growth data used harvest day as the repeated measure and animal as the subject. Single df contrasts were constructed for day 0 vs. day 28, day 0 vs. day 56, day 28 vs. day 56, M vs. A, and C vs. Z. Treatment impacted (P ≤ 0.05) live ADG; contrasts indicated A (1.33) was greater than M (0.14 kg), and Z (1.12) was greater than C (0.82 kg). Similarly, carcass ADG differences (P < 0.01) indicated A (1.04) was greater than M (0.36 kg), and Z (1.35) was greater than C (0.71 kg). Intake level altered BW and empty body weight (EBW); M cattle had reduced BW and EBW (P < 0.01, 585 and 540 kg) than A cattle (647 and 597 kg). Cattle fed at M had less carcass and internal cavity mass (P < 0.01, 359 and 79.4 kg) than A cattle (394 and 93.5 kg). Liver mass was reduced by M feeding (P < 0.01; M-5.03, A-6.69 kg) and Z treatment (P < 0.01; Z-5.64, C-6.06 kg). Moreover, mass of total splanchnic tissue was less (P < 0.01) for M cattle than A cattle (59.8 vs. 72.5 kg). Dressed carcass yield was greater (P < 0.01) for Z than C cattle (63.5 vs. 61.6%). Cattle fed at M had less 12th rib s.c. fat, lower numerical U.S. yield grades (P < 0.01; M-1.71 cm and 3.3, A-2.46 cm and 4.3) and lower numerical Canadian yield grades (P < 0.01; 51.9 vs. 53.9% for M and A, respectively) than A cattle. Results indicate that energy intake level and Z supplementation influence live and carcass growth, carcass transfer, kill yields, and carcass characteristics across time.