Mg Of Zeranol Research Articles

354 Effect of Finishing System on Growth, Efficiency, and Carcass Quality of Dairy × Beef Hybrids

Abstract Our objective was to determine how calf-fed or yearling finishing systems affect the performance and efficiency of dairy-beef crossbred steers. Dairy-beef hybrid steers were acquired from Land O’ Lakes Calf Milk Research Facility at Grey Summit, Missouri at 12-wk (BW /SD) of age and transported to Willard Sparks Beef Research Center (WSBRC). Upon arrival at WSBRC, steers were weighed, vaccinated, treated for parasites, and implanted with 36 mg of zeranol (Ralgro). Alternating groups of steers were placed either directly on finishing diets (FIN) or on high-quality pasture and supplementation for 5 to 6 mo before returning to WSBRC for finishing (GRW/FIN). Steers in FIN were grown on successively higher energy growing diets through d 112, stepping up to a 20% roughage growing diet from d 28 to 112. On d 112, FIN steers were transitioned to a 12% roughage finishing diet. A final 8% roughage finishing was fed to FIN steers from d 224 to slaughter. Steers in FIN were reimplanted with Ralgro on d 56, Component TE-IS (80 mg trenbolone acetate, 16 mg estradiol, and 29 mg tylosin tartrate; Elanco US, Greenfield, IN) on d 112, and Component TE-S (200 mg progesterone, 20 mg estradiol benzoate, 29 mg tylosin tartrate; Elanco) on d 224. Steers in GRW/FIN were returned to WSBRC, weighed, and processed when they reached 312 ± 7.0 kg. Steers in GRW/FIN were implanted with Component TE-IS at the start of finishing, and Component TE-S on d 120. Steers in GRW/FIN were stepped up to the finishing diet when they reached 407 ± 6.0 kg. Finishing diets for the final 28 d for FIN and GRW/FIN included ractopamine hydrochloride at a rate of 300 mg·steer-1·d-1. At WSBRC, steers within each finishing system were sorted by BW into 4 to 5 head pens. Initial and terminal BW were greater (P < 0.01) in steers in the GRW/FIN finishing system. Body weight at reimplant was greater (P < 0.01) for FIN. Steers in the GRW/FIN system were on feed for fewer (P < 0.01) days compared with FIN steers. Average daily gain (ADG) and DMI (kg·steer-1·d-1) were greater (P < 0.01) for GRW/FIN. Steers in GRW/FIN had a greater (P < 0.02) feed:gain ratio than those placed directly into a finishing system. There were no differences (P < 0.10) in USDA Yield Grade, marbling, ribeye area (REA), or back-fat thickness (BFT) between finishing systems. Steers in FIN had a greater (P < 0.01) dressing percentage (DP) and lighter (P < 0.01) hot carcass weight than those for GRW/FIN. Finishing system has an impact on performance and efficiency of dairy-beef hybrid steers, but minimal impact on carcass quality.

265 Manger Space Restriction Does not Negatively Impact Growth Efficiency of Feedlot Heifers Program fed a Concentrate-Based Diet to Gain 1.36 kg Daily

Abstract The objective of this research was to determine the influence manger space restriction had on program fed feedlot heifers during the growing phase. Charolais × Angus heifers [initial body weight (BW) = 329 ± 22.1 kg] were used in a 109-d backgrounding phase study. Heifers were received from a ranch in western South Dakota approximately 60 days before study initiation. Initial processing (53 days before study initiation) included individual BW measurement, application of a unique identification tag, vaccination against viral respiratory pathogens (Bovi-Shield Gold 5, Zoetis, Parsippany, NJ) and clostridial species (Ultrabac/Somubac 7, Zoetis), and administration of doramectin pour-on (Dectomax, Zoetis) for control of internal and external parasites. All heifers were administered 36 mg of zeranol (Ralgro, Merck Animal Health, Madison, NJ) at study initiation. Upon study initiation, heifers were assigned to 1 of 10 pens (n = 5 pens/treatment with 10 heifers/pen) in a randomized complete block design (blocked by location). Each pen was randomly assigned to 1 of 2 treatments: 20.3 cm (8IN) or 40.6 cm (16IN) of linear bunk space/heifer. Heifers were individually weighed on days 1, 14, 35, 63, 84 and 109. Heifers were programmed to gain 1.36 kg daily based on predictive equations for a medium frame steer calf set forth by the California Net Energy System. To calculate predictive values, a final BW of 575 kg was assumed to be the mature BW of the heifers and tabular net energy values of 2.05 NEm and 1.36 NEg from d 1 to 22, 2.00 NEm and 1.35 NEg from d 23 to 82, and 1.97 NEm and 1.32 NEg from d 83 to 109 were used, because of ingredient inventory changes. Data were analyzed using the GLIMMIX procedure of SAS 9.4 with manger space allocation as the fixed effect and block as the random effect. No differences (P > 0.35) were observed between 8IN or 16IN heifers for initial BW, final BW, average daily gain, dry matter intake, feed efficiency, variation in daily BW gain (within pen standard deviation) or applied energetic measures. No differences (P > 0.50) were observed between treatments for morbidity. Although not statistically analyzed, 8IN heifers appeared to have looser stools during the first two weeks compared with the 16IN heifers. These data suggest restricting manger space allocation from 40.6 cm to 20.3 cm did not negatively influence gain efficiency or the efficiency of dietary net energy utilization in heifers programmed fed a concentrate-based diet to gain 1.36 kg daily. The use of tabular net energy values and required net energy of maintenance and retained energy equations are an effective means to program cattle to a desired daily rate of gain during the growing phase.

Evaluation of Growth Performance, Efficiency of Dietary Net Energy Utilization, and Carcass Trait Responses of Heavy Finishing Lambs Administered 12 mg of Zeranol Subcutaneously in the Ear 59 d before Harvest

The objective of this research was to determine the influence of implanting heavy wether lambs with 12 mg of zeranol (1 pellet Ralgro, Merck Animal Health. Madison, NJ, USA) 59 d before harvest. Average daily gain (ADG), feed efficiency, and carcass merit were evaluated. Polypay and crossbred wethers (n = 32) were equally divided into two treatment groups: non-implanted; (CON) or implanted with 12 mg of zeranol (IMP) in a randomized complete block design. Sixteen pens were used, resulting in eight replicate pens per treatment. Wethers were fed a finishing diet consisting of cracked corn, soybean meal, and soybean hulls ad libitum for 59 d. Lambs had access to clean water at all times from water fountains. Lambs were weighed on d -1, 1, 14, and 59. On d 59, 16 lambs (8 lambs/treatment) were harvested in the South Dakota State University Meat Lab. Hot carcass weight (HCW), dressing percent (DP), rib fat, body wall thickness, loin eye area, boneless closely trimmed retail cut percentages, and yield grades were recorded. Final body weight (BW), cumulative ADG, and gain efficiency were greater (p ≤ 0.01) for implanted lambs by 2.9%, 25.0%, and 35.2%, respectively, while dry matter intake (DMI) was unaffected by implant treatment (p = 0.18); thus, the efficiency of dietary net energy utilization was increased for IMP (p ≤ 0.01). No appreciable differences were noted (p ≥ 0.17) between treatments for any carcass traits measured. These results indicate that zeranol improves growth performance in heavy finishing lambs without detriment to carcass quality, which implies that producers can improve profitability due to increased gains and efficiency.

41 Effect of Finishing System on Growth, Efficiency, and Carcass Quality of Dairy × Beef Hybrids

Abstract Our objective was to determine the effect of calf-fed or yearling finishing systems on the performance of dairy-beef crossbred steers. Dairy-beef hybrid steers were acquired from Land O’ Lakes Calf Milk Research Facility at Grey Summit, Missouri at 12-weeks of age and transported to Willard Sparks Beef Research Center (WSBRC). Upon arrival at WSBRC, steers were weighed, vaccinated, treated for parasites, and implanted with 36 mg of zeranol (Ralgro). Alternating groups of steers were placed either directly on finishing diets (FIN) or on high-quality pasture and supplementation for 5 to 6 mo before returning to WSBRC for finishing (GRW/FIN). Once GRW/FIN steers reached 312 ± 7 kg, the steers were returned to WSBRC, weighed, and processed. At WSBRC, steers within each finishing system were sorted by BW into 4 to 5 animal pens. Steers in FIN were re-implanted with Ralgro on d 56, Component TE-IS (80-mg trenbolone acetate,6-mg estradiol, and 29-mg tylosin tartrate; Elanco US, Greenfield, IN) on d 112, and Component TE-S (200-mg progesterone, 20-mg estradiol benzoate, 29-mg tylosin tartrate; Elanco) on d 224. Steers in GRW/FIN were implanted with Component TE-IS at the start of finishing, and Component TE-S on d 20. Steers in FIN were grown on successively greater energy growing diets through d 112, stepping up to a 20% roughage growing diet (18.4% CP and 2.4 Mcal NEg/kg from d 28 to 112. On d 112, FIN steers were transitioned to a finishing diet consisting of 12% roughage, 12% crude protein, and 1.3 Mcal NEg/kg. A final finishing diet (8% prairie hay, 20% Sweet Bran and 62% dry-rolled corn) was fed to FIN steers from d 224 to slaughter. Steers in GRW/FIN were stepped up to the finishing diet when they reached 407 ± 6 kg. Finishing diets for the final 28 d for FIN and GRW/FIN included ractopamine hydrochloride at a rate of 300 mg·steer-1·d-1. Initial and terminal BW were greater (P < 0.01) in steers in the GRW/FIN finishing system. Body weight at reimplant was greater (P < 0.01) for FIN. Steers in the GRW/FIN system were on feed for fewer (P < 0.01) days compared with FIN steers. Average daily gain (ADG) and DMI (kg·steer-1·d-1) were greater (P < 0.01) for GRW/FIN. Steers in GRW/FIN had a greater (P ≤ 0.02) feed:gain ratio than those placed directly into a finishing system. There were no differences (P ≥ 0.10) in USDA Yield Grade, marbling, ribeye area (REA), or back-fat thickness (BFT) between finishing systems. Steers in FIN had a greater (P < 0.01) dressing percentage (DP) and lighter (P ≤ 0.01) hot carcass weight (HCW) than those for GRW/FIN. Finishing system has an impact on performance and efficiency of dairy-beef hybrid steers, but minimal impact on carcass quality.

Manger space restriction does not negatively impact growth efficiency of feedlot heifers program fed a concentrate-based diet to gain 1.36 kg daily.

The objective of this research was to determine the influence manger space restriction had on program-fed feedlot heifers during the growing phase. Charolais × Angus heifers [initial body weight (BW) = 329 ± 22.1 kg] were used in a 109-d backgrounding study. Heifers were received approximately 60 d prior to study initiation. Initial processing (53 d before study initiation) included individual BW, application of an identification tag, vaccination against viral respiratory pathogens and clostridial species, and administration of doramectin pour-on for control of internal and external parasites. All heifers were administered 36 mg of zeranol at study initiation and were assigned to 1 of 10 pens (n = 5 pens/treatment with 10 heifers/pen) in a randomized complete block design (blocked by location). Each pen was randomly assigned to 1 of 2 treatments: 20.3 cm (8IN) or 40.6 cm (16IN) of linear bunk space/heifer. Heifers were individually weighed on days 1, 14, 35, 63, 84, and 109. Heifers were programmed to gain 1.36 kg daily based on predictive equations set forth by the California Net Energy System. To calculate predictive values, a final BW of 575 kg was assumed to be the mature BW of the heifers and tabular net energy values of 2.05 NEm and 1.36 NEg from days 1 to 22, 2.00 NEm and 1.35 NEg from days 23 to 82, and 1.97 NEm and 1.32 NEg from days 83 to 109 were used. Data were analyzed using the GLIMMIX procedure of SAS 9.4 with manger space allocation as the fixed effect and block as the random effect. No differences (P > 0.35) were observed between 8IN or 16IN heifers for initial BW, final BW, average daily gain, dry matter intake, feed efficiency, variation in daily weight gain within each pen or applied energetic measures. No differences (P > 0.50) were observed between treatments for morbidity. Although not statistically analyzed, 8IN heifers appeared to have looser stools during the first 2 weeks compared to the 16IN heifers. These data suggest restricting manger space allocation from 40.6 to 20.3 cm did not negatively influence gain efficiency or the efficiency of dietary net energy utilization in heifers programmed fed a concentrate-based diet to gain 1.36 kg daily. The use of tabular net energy values and required net energy of maintenance and retained energy equations are effective means to program cattle to a desired rate of daily gain during the growing phase.

165 The effects of feeding lasalocid in combination with zeranol implants on performance and carcass traits in hair sheep

Abstract The objective of this experiment was to determine the effects of dietary inclusion of lasalocid in combination with zeranol implants on the performance and carcass characteristics of hair sheep. Thirty wether hair lambs (BW = 25.8 + 4.6 kg) were stratified by BW and BCS and randomly assigned to 1 of 2 experimental treatments in a randomized complete block design. The treatments included no implant or ionophore (CON); and the experimental treatment, receiving the ionophore lasalocid (Bovatec® 91; Zoetis, Kalamazoo, MI) and anabolic zeranol implants (Ralgro®; MSD Animal Health, Spartan, RSA; LZ). Lambs on the LZ treatment received 12 mg of zeranol on d 0, 56, and 112, unless lambs were harvested prior to day 112, and consumed an average of 35 mg per day of lasalocid. Lambs had ad libitum access to feed and water throughout the experiment and were housed in individual, slatted floor pens. Performance data were collected on d 0, 14, 28, 56, 84, and at harvest. After d 84, harvest dates were selected and lambs were harvested by block based on proximity to ideal harvest weight and fat thickness. Lasalocid in the diet combined with zeranol implants increased final BW by 14.2% in comparison to CON (P < 0.01). Overall ADG was increased by 36.2% (P < 0.01), and overall G:F was improved by 24.4% for LZ when compared to CON (P = 0.01). There was no difference in overall DMI between treatments (P = 0.13). Hot carcass weight (HCW; P < 0.01), and loin eye area (LEA; P < 0.01) were also greater for the LZ treatment. Dietary inclusion of lasalocid in combination with zeranol implants improved overall BW, ADG, and feed efficiency as well as HCW and LEA in hair sheep.

166 The effects of feeding lasalocid in combination with zeranol implants on performance and carcass traits in hair sheep

Abstract The objective of this experiment was to determine the effects of dietary inclusion of lasalocid in combination with zeranol implants on the performance and carcass characteristics of hair sheep. Thirty wether hair lambs (BW = 25.8 + 4.6 kg) were stratified by BW and BCS and randomly assigned to 1 of 2 experimental treatments in a randomized complete block design. The treatments included no implant or ionophore (CON); and the experimental treatment, receiving the ionophore lasalocid (Bovatec® 91; Zoetis, Kalamazoo, MI) and anabolic zeranol implants (Ralgro®; MSD Animal Health, Spartan, RSA; LZ). Lambs on the LZ treatment received 12 mg of zeranol on d 0, 56, and 112, unless lambs were harvested prior to day 112, and consumed an average of 35 mg per day of lasalocid. Lambs had ad libitum access to feed and water throughout the experiment and were housed in individual, slatted floor pens. Performance data were collected on d 0, 14, 28, 56, 84, and at harvest. After d 84, harvest dates were selected and lambs were harvested by block based on proximity to ideal harvest weight and fat thickness. Lasalocid in the diet combined with zeranol implants increased final BW by 14.2% in comparison to CON (P < 0.01). Overall ADG was increased by 36.2% (P < 0.01), and overall G:F was improved by 24.4% for LZ when compared to CON (P = 0.01). There was no difference in overall DMI between treatments (P = 0.13). Hot carcass weight (HCW; P < 0.01), and loin eye area (LEA; P < 0.01) were also greater for the LZ treatment. Dietary inclusion of lasalocid in combination with zeranol implants improved overall BW, ADG, and feed efficiency as well as HCW and LEA in hair sheep.

Effects of using increasingly aggressive implant protocols on feedlot performance and carcass characteristics of calf-fed steers

<h2>ABSTRACT</h2> Three experiments evaluated aggressive implant strategies to better understand implant duration and allow for maximum return on implant investment in feedlot steers. Crossbred steers (n = 1,350; 282 kg initial BW, SD=8) were fed for an average of 215 d (Exp. 1). Treatments were Revalor-IS (80 mg of trenbolone acetate and 16 mg of estradiol) or Revalor-XS (200 mg of trenbolone acetate and 40 mg of estradiol) initially followed by 1 or 2 consecutive Revalor-200 (200 mg of trenbolone acetate and 20 mg of estradiol) implants (6 replications). Crossbred steers (n = 1,513; 265 kg initial BW, SD=18) were fed for an average of 208 d (Exp. 2). Treatments were (1) Revalor-G (40 mg of trenbolone acetate and 8 mg of estradiol) on d 0, Revalor-IS on d 50, and Revalor-200 on d 140; (2) Ralgro (36 mg of zeranol) on d 0 and Revalor-XS on d 50; and (3) Revalor-XS on d 0 and Revalor-200 on d 140 (5 replications). Holstein steers (n = 1,832; 144 kg initial BW, SD=11) were fed for an average of 360 d (Exp. 3). Treatments were (1) Ralgro on d 0, Revalor-IS on d 120, and Revalor-S on d 240; (2) Ralgro on d 0 and Revalor-XS on d 120; (3) Ralgro on d 0, Revalor-IS on d 60, and Revalor-XS on d 160; and (4) Revalor-XS on d 0 and Revalor-XS on d 160 (6 replications). In all 3 experiments, final BW, ADG, and HCW were not affected by treatment (<i>P</i> ≥ 0.12). Increasingly aggressive implant protocols have limited effects on feedlot and carcass performance of beef and Holstein steers.

Effects of timing of anabolic implant insertion on growth and immunity of recently weaned beef steers.

We evaluated the effects of timing of estrogenic implant insertion, relative to weaning, on growth performance and measurements of innate and humoral immunity of beef calves. On d -14, Angus × Simmental crossbred steers ( = 48; BW = 217 ± 5 kg; age = 191 ± 3 d) were stratified by BW, age, and cow parity and randomly assigned to receive no implant (NOIP) or 36 mg of zeranol on d -14, 0, or 14, relative to weaning (IP-14, IP0, and IP+14, respectively; 12 steers/treatment). From d -14 to 0, cow-calf pairs remained on a single, tall-fescue pasture with no access to concentrate supplementation. Steers were weaned on d 0, stratified by treatment and BW, and then allocated into 1 of 16 drylot pens to receive daily free-choice access to a corn silage-based diet during the preconditioning phase (d 0 to 56). Steers were vaccinated against infectious bovine rhinotracheitis (IBRV), bovine viral diarrhea virus (BVDV), and on d -27 and 0. From d 56 to 252 (postpreconditioning phase), steers remained in their respective feedlot pens and were provided free-choice access to corn silage-based growing (d 56 to 167) and finishing total mixed rations (d 168 to 252). Body weight on d 0 did not differ among treatments ( ≥ 0.29) but was greater for IP-14 and IP0 than NOIP and IP+14 steers on d 14, 42, and 56 ( ≤ 0.05). Treatment effects were not detected for G:F and DMI from d 0 to 56 ( ≥ 0.34), but ADG from d -14 to 56 was greater for IP-14 compared to NOIP ( ≤ 0.05) and intermediate for IP0 and IP+14 steers. Plasma IGF-1 concentrations were greater for IP-14 than NOIP ( ≤ 0.05) and intermediate for IP0 and IP+14 steers on d -7, 0, 14, and 21. Plasma concentrations of cortisol and haptoglobin and serum titers against BVDV types 1a and 2 did not differ among treatments from d 0 to 56 ( ≥ 0.37). However, serum IBRV titers were greater for IP+14 than NOIP, IP-14, and IP0 steers ( ≤ 0.02). On d 252, BW was greater for IP-14 and IP0 than NOIP steers ( ≤ 0.05) and intermediate for IP+14 steers, but ADG and G:F from d 57 to 252 and carcass characteristics at slaughter did not differ among treatments ( ≥ 0.16). Thus, the 36-mg zeranol implant did not elicit an inflammatory response or affect the overall vaccine response of steers (except for IBRV titers). However, growth of steers during a 56-d preconditioning period was enhanced by administering 36-mg zeranol implant 14 d before weaning, without affecting subsequent postpreconditioning growth and carcass characteristics at slaughter.

Zeranol Induces Deleterious Effects on the Testes and the Prostate Gland of Mature Rats

Background. Endocrine disrupters have been shown to affect the male and female reproductive systems and to alter potential fertility. Objectives. This study was conducted to evaluate the effect of a continuous-release pellet containing 12 mg of zeranol for 30 days on the testes and the prostate gland of mature male rats. Results. Zeranol treatment induced significant decrease of the testes and the prostate gland weights which were associated with a remarkable atrophy of the testicular seminiferous tubules and prominent regression of the glandular compartment of the prostate gland. However, zeranol treatment increased the thickness of the periductal layer of stromal cells of the prostate gland from a thin layer that express intense immunostaining of SM-actin and mild vimentin to a thicker layer of cells that exhibited intense immunostaining for both SM-actin and vimentin. Conclusion. These findings suggest that zeranol-induced changes to the prostate gland could result from either a direct effect of zeranol on the prostate gland or an indirect effect by interfering with testosterone production through disruption of testicular function.

Zeranol: doping offence or mycotoxin? A case‐related study

Zeranol ((7R,11S)-7,15,17-trihydroxy-11-methyl-12-oxabicyclo[12.4.0]octadeca-1(14),15,17-trien-13-one, also referred to as 7α-zearalanol, Ralone®, Frideron®, Ralgro®, etc.) is a semi-synthetic estrogenic veterinary drug with growth-promoting properties. Its use regarding animal husbandry has been prohibited in the European Union since 1981 and, due to its anabolic effects, it is further recognized as a banned substance in sport. Numerous studies were conducted concerning the identification of the illicit application of zeranol to domestic livestock. These studies also considered the natural occurrence of zeranol as a metabolite of the mycotoxin zearalenone and the issue of differentiating both scenarios, i.e. illegal use or unintended contamination. Human sports drug testing authorities are facing comparable challenges since the deliberate misuse of the (for human application non-approved) drug should be discriminated from adverse analytical findings resulting from the biotransformation of the mycotoxin zearalenone possibly ingested with contaminated food. The active drug (zeranol), its major human metabolites (zearalanone, 7β-zearalanol) and the mycotoxin (zearalenone) plus its major and unique metabolic products (α-zearalenol, β-zearalenol) have been monitored in routine doping controls by means of validated gas chromatography-(tandem) mass spectrometry (GC-(MS/)MS) methods since 1996, and between 2005 and 2010 four samples providing suspicious signals were detected. In agreement with literature data, in vitro metabolism studies demonstrated the metabolic pathway from zearalenone towards zeranol (and common metabolites). In contrast, an administration study urine sample (collected after oral application of 20 mg of zeranol) yielded only ultra-trace amounts of zearalenone and its characteristic metabolites, which supported the assumption that a mycotoxin contamination caused the finding of zeranol in the doping control specimens rather than a misuse of the anabolic agent.

Effects of Method and Timing of Castration and the Use of an Estrogenic Growth Stimulant on Weight Gain of Bull Calves

Two experiments were conducted to determine the effects of method and timing of castration on performance of bull calves. In Exp. 1, 2- to 3-mo-old bulls (n = 168) were left intact or were castrated either surgically or with rubber bands, and all calves were implanted with 36mg of zeranol. Intact bulls were castrated at weaning (7 to 8 mo) with large rubber bands and all calves were re-implanted with 36mg of zeranol. In Exp. 2, 139 bulls were assigned at birth to the following treatments: banded, banded and implanted (36mg zeranol), or left intact. Four weeks before weaning, intact bulls were castrated with large rubber bands and all animals were implanted. In Exp. 1, ADG from 2 mo to weaning was not different for implanted bulls compared with bulls castrated and implanted. The ADG of implanted bulls that were banded at weaning was less (P < 0.05) during the following 50 d compared with bulls castrated and implanted at 2 to 3 mo of age. In Exp. 2, intact bulls had similar BW 30 d before weaning compared with bulls that were castrated at birth or castrated and given an implant at birth. The BW of bulls that were banded 30 d before weaning was reduced (P < 0.01) at weaning compared with bulls banded at birth. It is concluded that intact bulls do not have an advantage in pre-weaning growth compared with bulls castrated and implanted at less than 3 mo of age. Castrating bulls at greater than 6 mo of age with large rubber bands decreased BW gains during the next 30 d.

Effects of Implant Programs on Buller Incidence, Feedlot Performance, and Carcass Characteristics of Yearling Steers

English and English × Continental crossbred steers (272 steers per pen; 4 pens per treatment) were used in a randomized complete block design to determine the effects of terminal implant type (Revalor S® [Hoechst-Roussel Vet, Somerville, NJ] and Component TES™ [Vet Life, Overland Park, KS]; each containing 24mg of estradiol-17β and 120mg of trenbolone acetate) and timing of terminal implant administration (d 1 or 50) on buller incidence, feedlot performance, and carcass characteristics. Steers either received Component TES™ (TES) or Revalor S® (RevS) on d 1 or 36mg of zeranol (Ralgro®; Schering-Plough, Omaha, NE) on d 1 and TES (Ral/TES) or RevS (Ral/RevS) on d 50. Steers receiving TES and RevS were not removed from the home pen on d 50, and all steers were harvested after 144 d. Bullers pulled during the first 50 d were returned to home pens on d 50 and were classified as a repull if removed again as a buller. The incidence of new bullers during the first 50 d did not differ (P=0.14) between steers receiving TES (2.3%), RevS (1.75%), or Ralgro® initially (1.42%; Ral/TES + Ral/RevS). There were fewer new bullers from d 50 to 144 for TES and Ral/TES than for RevS and Ral/RevS (P=0.02; 0.97% vs 1.88%, respectively) and also when steers received a terminal implant on d 1 compared with d 50 (P=0.01; 0.92% vs 1.93%, respectively); however, the overall incidence of new bullers did not differ (P>0.43) among treatments. Neither implant type nor timing influenced repull incidence from d 50 to 144 (P>0.45) or the overall incidence of total (new + repull) bullers (P>0.43). Steer DMI (implant type × timing, P=0.04) was least (P<0.02) for Ral/TES, intermediate for TES, and greatest RevS and Ral/RevS. Live and carcass-adjusted BW gain efficiencies were 2.4% greater (P<0.03) for TES or Ral/TES than for RevS or Ral/ RevS. Final BW, ADG, and hot carcass weight did not differ (P>0.19) among treatments. Steers receiving Ral/TES and Ral/RevS had a greater percentage of dark cutters (P<0.01), more Yield Grade 1 carcasses (P<0.01), and fewer Yield Grade 3 carcasses (P<0.01) than TES or RevS. Administering TES on d 1 or 50 resulted in improved gain efficiency, whereas overall buller incidence was not influenced by terminal implant type or timing. Administering either TES or RevS on d 50 increased the incidence of dark carcasses, resulted in more Yield Grade 1 and fewer Yield Grade 3 carcasses, and influenced when bullers developed but did not influence carcass quality grade distribution or overall buller incidence.

Use of melengestrol acetate-based treatments to induce and synchronize estrus in seasonally anestrous ewes.

Ten experiments utilizing 1,659 ewes were conducted to determine the potential of melengestrol acetate (MGA)-based treatments in inducing and synchronizing estrous activity in ewes during the nonbreeding season. In May or June, ewes were given .25 mg of MGA.ewe-1.d-1 or control diet and(or) a subsequent i.m. injection of zeranol, estradiol-17 beta, or oil vehicle. Fertile rams were introduced, and estrous and(or) lambing responses were determined. In Exp. 1, more (P < .01) ewes given MGA for 14 d followed by 5 mg of zeranol (i.m.) were in estrus than controls. Melengestrol acetate and zeranol independently induced estrus in Exp. 2, with MGA-treated ewes exhibiting the greatest lambing response (P < .05). The optimum duration of feeding MGA was 8 d vs 11 or 14 d (Exp. 3). In Exp. 4, as the dose of zeranol increased, synchrony of estrus increased but lambing response decreased. A dose of 1.25 mg of zeranol represented a compromise in estrous and lambing response and was determined to be optimally effective when given 54 h after the last feeding of MGA (Exp. 5). Shortcomings in lambing responses were treated in Exp. 6 by supplementing ewes with MGA after breeding, which proved unsuccessful, and in Exp. 7 by substituting estradiol-17 beta for zeranol, which proved effective when given 54 h after the last feeding of MGA (Exp. 8). In Exp. 9, use of MGA + estradiol increased (P < .05) the estrous and subsequent lambing response of 30-d postpartum ewes temporarily weaned of their lambs. In contrast, lambing response of 90-d postpartum ewes treated with MGA + estradiol was not increased by temporary removal of lambs (Exp. 10). These data collectively support the hypothesis that treatment of ewes with MGA + estradiol is an effective and practical approach for inducing and synchronizing a fertile estrus in ewes during the non-breeding season.

Efeitos de produtos anabolizantes sobre a qualidade do sêmen de touros

Com a finalidade de se avaliar o efeito de esteróides anabolizantes sobre a qualidade do sêmen de touros, foram testados 3 tratamentos em 9 touros adultos (idades de 3 a 5 anos). Os grupos I e II receberam implantes subcutâneos na base da orelha, sendo implantados no grupo I, 36mg de zeranol e no grupo II 24mg de dietiletilbestrol (DES), enquanto o grupo III permaneceu como testemunha. Foram realizadas 31 coletas de sêmen semanais, tendo sido a primeira, uma semana antes do implante. Não se verificaram alterações em nenhuma das características do sêmen devido aos tratamentos. Os três grupos tiveram ganhos de peso similares. Conclui-se que, nas condições em que o experimento foi realizado, não houve efeito dos anabolizantes na qualidade do sêmen. Caso tenham ocorrido alterações genitais mais discretas, essas foram subclínicas ou não foram detectadas devido ao número de unidades experimentais por tratamento.

Influence of incremental zeranol implant doses on the chemical and physical characteristics of third metacarpal bone and chemical composition of liver and soft tissue from feedlot steers.

Chemical and physical characteristics of third metacarpal bones and liver and rib soft tissue composition from feedlot steers were determined. Steers were selected (32 from each experimental location) to represent the range in slaughter weight and composition for each treatment group in three (total n = 1,088) feedlot experiments. Steers were implanted with 0, 24, 36, 48, 60, 72, 84, or 96 mg of zeranol at approximately 140 d before slaughter. Cattle at each location were fed for the same number of days and slaughtered as a group. Zeranol dose had no effect on the chemical composition of bone, liver, or rib soft tissue with the following exceptions: zeranol decreased (P < .01) bone Ca concentration and increased (P < .07) liver P concentration. Zeranol implantation decreased medullary cavity anterioposterior (AP) diameters and AP cortical width (P < .08). Loads withstood by the bones up to flexure (P < .08) and the strain at flexure (P < .09) were inversely related to the quadratic of zeranol dose. However, modulus of elasticity at flexure and breaking increased numerically with zeranol dose. Stress withstood by bones at flexure was greater (P < .09) for implanted steers. Strain data indicate that metacarpals from steers receiving zeranol would exhibit less deformation upon loading to flexure (P < .09) than controls. These data indicate that administration of intermediate doses of zeranol altered bone deposition of Ca, which resulted in modified third metacarpal physical and mechanical characteristics.

Melengestrol acetate and norgestomet for the induction of synchronized estrus in seasonally anovular ewes.

Two commercially available progestogen products for cattle, melengestrol acetate (MGA) and norgestomet (SMB), were evaluated for their ability to induce synchronized estrus in anovulatory ewes. Seasonally anestrous ewes (n = 232) were randomly assigned to one of seven treatments: 1) control (C); 2) MGA only (OMGA; .3 mg of MGA/d); 3) MGA+zeranol (RMGA; 2.5 mg of zeranol); 4) MGA+PG-600 (PMGA; 400 IU of PMSG + 200 IU of hCG in a 5-mL dose); 5) SMB only (OSMB); 6) SMB + zeranol (RSMB); and 7) SMB + PG-600 (PSMB). Treatments were initiated 10 d before breeding. Immediately preceding progestogen treatment, RMGA and RSMB ewes were given a single i.m. injection of zeranol. Concomitant to progestogen removal, PMGA and PSMB ewes were given a single i.m. injection of PG-600. On May 4, 1992, all treatment groups were combined into one breeding group for a 30-d breeding period. Mating at synchronized estrus was greater (P < .001) for progestogen-treated ewes. Within progestogen treatments, more (P < .001) SMB ewes than MGA ewes were marked within the first 5 d of breeding. Overall, there were no treatment differences in estrus response for the 30-d breeding period. Progestogen-treated ewes had a shorter (P < .001) mean interval from ram introduction to lambing. Fertility and prolificacy were not different for C, MGA, or SMB ewes. Ewes primed with zeranol before MGA or SMB treatment had fertility and intervals from ram introduction to lambing similar to those of ewes receiving an injection of PG-600 after progestogen treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of zeranol implanted during a postweaning weight gain test on testicular, semen, and endocrine characteristics of bulls

Summary At initiation of a 140-day postweaning weight gain test, Angus bulls were assigned in equal numbers (n = 5) to 1 of 3 treatment groups to determine effects of implantation with zeranol, an estrogenic growth promotant, on selected reproductive characteristics. The bulls, whose age (mean ± sd) was 233 ± 20 days at initiation of the test (day 0), were implanted with 36 mg of zeranol on day 0, on days 0 and 60, or were not implanted. At day 140, scrotal circumference and testicular consistency were unaffected by zeranol implantation. Zeranol implantation did not affect the morphologic characteristics of semen samples collected by electroejaculation on day 159. There was no effect of zeranol treatment on paired weights of testes, epididymides, or vesicular glands from bulls at slaughter 47 to 68 days after day 140. Microscopic lesions associated with estrogenic exposure were not observed in accessory sex glands or epididymides of any bull. Histopathologic changes in the seminiferous epithelium were not induced by zeranol treatment. Implantation with zeranol did not affect body weight or hip weight at day 140 or carcass weight at slaughter. Plasma concentration of luteinizing hormone was increased (P = 0.04), whereas testosterone concentration tended to be less (P = 0.08) in both groups of zeranol-implanted bulls after administration of gonadotropin-releasing hormone on day 140.

Effects of different doses of zeranol on growth, hemoglobin, and carcass traits in veal calves1

Effects of different doses of zeranol on ADG, hemoglobin (Hb), feed efficiency (FE), and carcass traits were evaluated in special-fed veal calves in two trials. On d 0, calves were implanted subcutaneously in the middle third of the ear with either 0 (control, placebo pellet), 12, 24, 36, or 48 mg of zeranol. Trial 1 was conducted from February through May 1990 with 120 Holstein bull calves (17 to 21 d of age on d 0) and Trial 2 was conducted from May through August 1991 with 100 Holstein bull calves (24 to 28 d of age d 0). Calves were fed on an individual calf basis. Calves in Trial 1 that were implanted with 48 mg of zeranol had improved FE (P < .05) and ADG (P < .05) during Period 1 (0 to 43 d). No significant differences in ADG or FE were observed among treatments in Trial 2. Hemoglobin levels at slaughter averaged 7.88 +/- .096 and 8.19 +/- .149 g/dL over all treatments for Trials 1 and 2, respectively. The only postslaughter trait affected by zeranol dose was testicular weight. In both trials, testicular weight at slaughter decreased (P < .05) with increasing doses of zeranol. Dressing percentage tended to be higher for 48-mg implants than for controls but the difference was not significant. There were no significant zeranol dose effects on longissimus muscle area, flank color, carcass conformation, or percentage of fore- vs hind-quarter weight. These results indicated that higher doses of zeranol improved ADG and FE during the first 6 wk after the trial period (to 8 wk of age), decreased testicular weight, and increased hide-on carcass dressing percentage for calves implanted with 48 mg of zeranol compared with those that received 0 mg of zeranol.

Growth and slaughter characteristics of ram and wether lambs implanted with zeranol

Forty-nine Columbia ram and wether lambs born in April 1990 and 46 born in April 1991 were studied to determine the effects of zeranol implants on growth, difficulty of pelt removal, and carcass characteristics. Implanting ram and wether lambs once (1990) or twice (1991) with 12 mg of zeranol did not change live weight or ADG but gain/feed decreased (P < .05) in ram lambs slaughtered at approximately 50 kg. Testes weight was reduced approximately 50% by implanting. Two implants reduced (P < .05) the force needed to pull the pelt from the hind legs of ram lambs, but implanting tended to increase the force required to pull the pelt from wether lambs. Data for pelt weight, force required to pull the pelt, percentage of the carcass in the shoulder or splenius muscle, and Warner-Bratzler shear values showed that zeranol implants resulted in ram lambs becoming more like wethers and wether lambs becoming more like rams. Implanting with zeranol did not affect closure of the metacarpal growth plate in ram or in wether lambs. Difficulty of pelt removal can be reduced by implanting ram lambs with 12 mg of zeranol at approximately 114 d of age and reimplanting zeranol 28 d later.