Effects of trenbolone acetate on carcass characteristics and serum testosterone and cortisol concentrations in bulls and steers on different management and implant schemes

The objective of this study was to determine the effects of different implanting schemes on serum testosterone and cortisol concentrations, and carcass traits of bulls and steers implanted with trenbolone acetate (TBA) and zeranol (Z). Twenty Polled Hereford bulls were randomly assigned to one of three treatments after birth. Five calves served as nonimplanted control bulls (NIB). Nine bulls were implanted (IB) with 140 mg of TBA and 36 mg of Z at about 1 mo of age and reimplanted with both compounds 10 wk later. When IB calves were about 21 wk of age, the TBA implant was removed and calves were reimplanted with Z every 10 wk until slaughter. Six calves were castrated at 3 wk of age and implanted (IS) with TBA and Z every 10 wk until slaughter. Blood samples from each animal were obtained at 14-d intervals beginning at 14 wk of age and serum cortisol (C) and testosterone (T) concentrations were determined. The NIB had higher C levels than IB or IS (P less than .05) during the preweaning period. During the finishing period, there were no differences in C concentrations between NIB and IB; however, IS had lower levels (P less than .05) than both bull treatments. Serum T concentrations began to increase about 12 wk later (42 vs 30 wk, respectively) in IB compared with NIB. Testicular size was smaller (P less than .05) in IB than in NIB. No differences (P greater than .05) were observed in carcass characteristics. Taste-panel scores were not different among treatments. In conclusion, implanting schemes using TBA and Z lowered serum levels of C and delayed puberty in bulls; however, they did not alter carcass characteristics or eating quality.     

Management systems for Holstein steers that utilize alfalfa silage and improve carcass value.

Two trials were conducted to evaluate the effect of two-phase feeding systems using alfalfa silage or pasture on the performance and carcass characteristics of Holstein steers. During the growing phase (98 d) of Trial 1, steers received alfalfa silage at either 40, 22, or 7% of the DMI. During the growing phase of Trial 2, steers received alfalfa silage at either 39 or 8% of their DMI (140 d) or grazed an orchardgrass/ryegrass pasture (175 d). During the finishing phase, all steers received a 90% concentrate diet until they reached a small degree of marbling at the 12th rib as predicted by ultrasonic attenuation. In Trial 1, one-half were initially implanted with zeranol and reimplanted with trenbolone acetate and estradiol (TBA+E) after 98 d. In Trial 2, one-half were implanted twice with TBA+E at a 120-d interval. Trial 1 average daily gains (kilograms) for the 40, 22, and 7% alfalfa silage treatments were 1.14, 1.25, and 1.38 in Period 1 (all different from each other at P less than .05); 1.31, 1.34, and 1.19 in Period 2; and 1.25, 1.25, and 1.26 overall. Trial 2 average daily gains (kilograms) for the 39, 8, and pasture treatments were 1.50, 1.71, and .92 for Period 1 (all different from each other at P less than .05); .93, .75, 1.11 for Period 2 (all different from each other at P less than .05); and 1.16, 1.17, and 1.03 overall (pasture different at P less than .05). No consistent effects of diet or implant on carcass characteristics were observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of estradiol, trenbolone acetate, or zeranol on growth rate, mammary development, carcass traits, and plasma estradiol concentrations of beef heifers.

The effect of a single implantation (on d 1) with one or two long-acting, biodegradable estradiol implants (1E or 2E) on plasma estradiol concentrations in beef heifers was determined. The growth rates of these (2E) heifers, and of heifers repeatedly implanted with trenbolone acetate (TBA) or zeranol (Z) on d 1, 84, 168, and 252 of the trial, were compared to growth rates of controls. Trenbolone acetate alone was compared to TBA + 2E, and 2E was compared to 1E. At a mean age of 84 d (d 1 of experiment), 81 Hereford x Friesian heifers were allocated at random to the following treatments: Control (n = 15); TBA (n = 15); 1E (n = 12); 2E (n = 15); Z (n = 13); or TBA + 2E (n = 11). Mean live weight (kg) prior to slaughter on d 368 and hot carcass weight (kg) for heifers assigned to treatment Groups 1 to 6, respectively, were 366 and 200, 391 and 212, 374 and 201, 386 and 207, 387 and 210, and 391 and 208 (residual SD = 30.3 and 20.2). Heifers assigned to both the 2E and Z treatments were heavier on d 368 (P less than .05) and had longer teats on d 279 (P less than .05), less pelvic fat (P less than .05), and heavier kidneys (P less than .005) than control heifers. Heifers assigned to the TBA treatment had shorter teats on d 279 (P less than .001) but greater final live weight (P less than .05) and carcass weight than control heifers. Heifers given TBA alone had more pelvic fat (P less than .05) and lighter kidneys (P less than .05) than those given TBA + 2E. Mean estradiol concentrations in both the ipsilateral and contralateral jugular veins of heifers assigned to the 2E and TBA + 2E treatments, and in the ipsilateral jugular veins of heifers given 1E, were greater (P less than .05) than those in control heifers; concentrations did not decline during the experiment.     

Skeletal muscle protein metabolism and serum growth hormone, insulin, and cortisol concentrations in growing steers implanted with estradiol-17 beta, trenbolone acetate, or estradiol-17 beta plus trenbolone acetate.

Skeletal muscle protein degradation, measured by urinary N tau-methylhistidine excretion, and circulating concentrations of growth hormone (GH), insulin (INS), and cortisol (CT) were monitored in steers before and after implantation with estradiol-17 beta (E2; 24 mg) and trenbolone acetate (TBA; 300 mg). Yearling crossbred steers (n = 43) were randomly assigned to four treatment groups in a 2 x 2 factorial arrangement: nonimplanted controls (C); TBA; E2; and TBA plus E2 (TBA+E2). A subgroup (Block 1) of 16 steers was bled on d -12, 31, and 72 after implanting. Deposition of skeletal muscle protein was markedly increased (P less than .001) by E2 and TBA+E2 treatment. This response occurred mainly within the first 40 d after implantation and declined (P less than .001) in concert with decreasing (P less than .01) concentration of serum E2. Anabolic steroid treatment did not affect the rate of skeletal muscle protein breakdown. There was no apparent relationship between reduced serum CT concentration (linear effect; P less than .01) in TBA-treated steers and skeletal muscle protein degradation rate. Blood concentration and pulse activity of INS were not affected by anabolic steroid administration. Both TBA- and TBA+E2-implanted steers displayed a linear decrease (P less than .05) in serum GH concentration over time, which was similar to C. Lowered mean GH concentration resulted from a reduction (TBA main effect; P less than .05) in pulse amplitude of GH. Unlike TBA, TBA+E2, and C, only E2 maintained serum GH concentrations over time. Although increased muscle protein deposition was evident in TBA+E2-treated steers, an obvious causal relationship between this response and circulating GH, INS, and CT was not revealed. These results do not support the concept that combined androgenic agent and estrogen administration effectively reduce bovine muscle protein degradation by static modulation of circulating endogenous anabolic and antianabolic hormones.     

Trenbolone acetate/estradiol combinations in feedlot steers: dose-response and implant carrier effects.

Two experiments were conducted at three locations to determine the correct dosage and carrier for trenbolone acetate (TBA) and estradiol (E2) implants in feedlot steers. In the dose-response experiment, 1,296 steers were allotted to six implant treatments (48 pens per location): control, 140 mg of TBA (140/0), 30 mg of E2 (0/30), 20 mg of TBA + 4 mg of E2(20/4), 80 mg of TBA + 16 mg of E2(80/16), and 140 mg of TBA + 28 mg of E2 (140/28). In the carrier experiment, 575 steers were allotted to five implant treatments (25 pens per location): control, 140 mg of TBA + 28 mg of E2 in lactose (140/28-LA), 140 mg of TBA + 28 mg of E2 in cholesterol (140/28-CH), 140 mg of TBA + 20 mg of E2 in LA (140/20-LA), and 200 mg of progesterone + 20 mg of E2 benzoate (SS, reimplanted). In both experiments steers were fed a finishing diet for 140 to 168 d. In the dose-response experiment, response to TBA alone (140/0) did not differ from control (P greater than .2). Estradiol alone (0/30) improved ADG by 7% (P less than .01) and tended to improve feed efficiency over control (3%, P = .17). The highest dosage (140/28) improved ADG by 18% (P less than .001) and feed efficiency by 10% (P less than .001) over control and 10% (P less than .001) and 7% (P less than .01) over E2 alone, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of zeranol and trenbolone acetate on testis function, live weight gain and carcass traits of bulls

The ability of zeranol and trenbolone acetate (trenbolone) to alter testis function, weight gain and carcass traits of young bulls was studied. In Exp. 1, the effects of age at initial zeranol implantation was determined. After a 235-d experimental period, sequential implantation (56-d intervals) beginning at 100 or 150 d of age had reduced testis growth (P less than .01), sperm production (P less than .01) and serum testosterone concentration in response to gonadotropin releasing hormone (GnRH; P less than .01). The 200-d age group was partially suppressed, while the 250-d age group was not affected. Body weights were similar to controls in all groups. In Exp. 2, bulls previously implanted with zeranol at 175 and 231 d of age received single implants of zeranol, trenbolone or trenbolone plus zeranol at approximately 300 d of age. At slaughter (135 d later), body weight and carcass characteristics in all treatments were similar to controls. However, trenbolone reduced sperm production (P less than .05), zeranol reduced sperm production and testes weight (P less than .05), but trenbolone plus zeranol was similar to controls. Mean testosterone response to GnRH was suppressed in all implant groups on d 65 (P less than .01), but only in trenbolone or trenbolone plus zeranol groups on d 112 (P less than .05). Results indicate that zeranol suppresses spermatogenesis and testosterone production if implanted before approximately 200 d of age. Reduction of endogenous testosterone without alteration of weight gain or carcass characteristics may be of benefit if behavioral or masculinity traits of bulls are altered. Also, it appears that no benefit is derived from implanting bulls with both trenbolone and zeranol.     

Effect of long or short acting anabolic agents, given singly or repeated, on growth rate and carcase weight of steers

A trial was carried out using 490, 12- to 15-month-old steers which were at pasture from April to November and then housed and fed grass silage and concentrates until sold live or slaughtered. Animals were allocated at random to one of the following treatments: (i) Control; (ii) implanted with 45 mg oestradiol -17 beta in silastic rubber in April; (iii) implanted with oestradiol in April and with 300 mg trenbolone acetate in April, August and November; (iv) implanted with 36 mg zeranol in April, August and November and (v) implanted with zeranol and trenbolone acetate in April, August and November. Daily liveweight gains were 0.69, 0.75, 0.78, 0.83 and 0.86 (+/- 0.02) kg, and carcase weights were 300, 306, 311, 316 and 321 (+/- 3.4) kg, for treatments (i) to (v), respectively. All implanted animals had significantly higher daily gains than control animals and an additive response was obtained where trenbolone acetate was used with oestradiol or zeranol. Pooled results for animals treated with oestradiol plus zeranol, with or without trenbolone acetate, show that the overall response for zeranol treated animals was higher than from the animals treated with oestradiol. Daily gains after the first, second and third implant period show a reduced response from the oestradiol implant for the final 63 days of the trial. This may have been caused by loss of some oestradiol implants from animals early in the trial.     

Effects of implants on daily gains of steers wintered on dormant native tallgrass prairie, subsequent performance, and carcass characteristics

Fall-weaned crossbred steer calves (n = 300; 184 +/- 2.9 kg) received either no implant (Control) or were implanted with Synovex-C (SC = 10 mg estradiol benzoate + 100 mg progesterone), Synovex-S (SS = 20 mg estradiol benzoate + 200 mg progesterone), or Revalor-G (RG = 8 mg estradiol-17beta + 40 mg trenbolone acetate) to determine the effects of implants on weight gain during winter grazing on dormant tallgrass prairie, subsequent grazing and finishing performance, and carcass characteristics. Steers grazed two dormant tallgrass prairie pastures from October 16, 1996, until March 29, 1997 (164 d), and received 1.36 kg/d of a 25% CP supplement that supplied 100 mg of monensin/steer. Following winter grazing, all steers were implanted with Ralgro (36 mg zeranol) and grazed a common tallgrass prairie pasture until July 17 (110 d). After summer grazing, all steers were implanted with Revalor-S (24 mg estradiol-17beta + 120 mg trenbolone acetate), and winter implant treatment groups were equally allotted to four feedlot pens. Steers were harvested November 17, 1997, after a 123-d finishing period. Daily gains during the winter grazing phase averaged .28, .32, .32, or .35 kg/d, respectively, for Control, SC, SS, or RG steers and were greater (P < .01) for implanted steers than for Controls. Summer daily gains were similar (1.05 +/- .016 kg/d; P > or = .61) for all treatment groups. Feedlot daily gains were also similar (1.67 +/- .034 kg/d; P > or = .21), with implanted steers weighing 14 kg more than Control steers (P = .05) at harvest, despite similar management during summer grazing and feedlot phases. Control steers tended (P = .06) to have lower yield grades. There were no differences (P = .99) in marbling between implanted and nonimplanted steers. Steers implanted during the wintering phase had increased skeletal and overall (P < .01) carcass maturities compared with nonimplanted steers, which resulted in more "B" and "C" maturity carcasses. Because carcass maturity score affects quality grade, the increased maturities of implanted steers resulted in a $9.04 decrease in carcass value/100 kg (P < .01) compared with Controls. The results of this study indicate that growth-promoting implants are efficacious for cattle wintered on dormant native range despite low daily gains. This increased weight is maintained through the summer grazing and feedlot phases; however, the benefit of the increased weight may be offset by decreased carcass quality grade and value due to increased carcass maturity.     

Effect of prenatal trenbolone acetate treatment on lamb performance and carcass characteristics

Forty-three pregnant Dorset and Dorset crossbred ewes were assigned randomly to a control group or implanted with either 300 mg trenbolone acetate (Low TBA) or 1,200 mg trenbolone acetate (High TBA) between d 40 and 60 of gestation. Adjusted weaning weights for ewe lambs were 23.3% less (P less than .10) with vs without TBA treatments. Postweaning ADG of ewe lambs was lower (P less than .05) but ADG of ram lambs was greater (P less than .05) for high TBA vs low TBA. Ewe lambs receiving high TBA had 19% less (P less than .05) gain per unit of feed than those receiving low TBA. Days on test for ewe lambs was greater (P less than .05) due to TBA treatment and for high TBA vs low TBA. Days on test for ram lambs was decreased (P less than .05) due to high TBA compared to low TBA. Subcutaneous fat over the ribeye and lower rib were greater (P less than .05) for high-TBA ewe lambs vs low-TBA ewe lambs. Percentage kidney and pelvic fat of ewe lambs was lower (P less than .05) due to TBA treatments. Ribeye area per unit of carcass weight was lower (P less than .05) in high-TBA ewe lambs vs low-TBA ewe lambs. Yield grade of ewe lambs was lower (P less than .05) for low TBA vs high TBA. Prenatal trenbolone acetate treatment of ewe lambs did not improve their subsequent postnatal growth performance and carcass traits. In addition, TBA implantation of the pregnant ewe produced dystocia and less milk production, as evidenced by the need for more lambs to be grafted.     

Effect of an implant of trenbolone acetate and estradiol on growth, feed efficiency, and carcass composition of Holstein and beef steers.

The effects of an implant of 140 mg of trenbolone acetate and 28 mg of estradiol (TBA + E2) on performance and carcass composition were evaluated with 72 individually fed steers. Holstein (n = 24), Angus (n = 24), and Angus x Simmental (n = 24) steer calves were allocated by breed and implant treatment to either an individual feeding pen (n = 36) or an electronic feeding door in a group pen (three pens with 12 animals per pen). Intake and refusal of the 85% concentrate diet were recorded daily. Animals were slaughtered when ultrasonic attenuation values of the longissimus muscle at the 12th rib reached .55, which is correlated with low Choice marbling. At slaughter, complete carcass measurements were taken and the right side of each carcass was separated into boneless wholesale cuts. Implanting with TBA + E2 improved (P less than .01) daily gain and feed efficiency. Daily gain was increased 17, 26, and 21% in Holstein, Angus, and crossbred steers, respectively. The implant increased overall daily protein and fat accretion 23%. Carcass conformation and dressing percentage were not affected (P greater than .05) by TBA + E2 treatment. Implantation with TBA + E2 had little effect on yield of wholesale boneless cuts when expressed as a percentage of carcass weight but increased absolute weight as a small degree of marbling by 6 to 40 kg.     

Use of trenbolone acetate and estradiol in intact and castrate male cattle: effects on growth, serum hormones, and carcass characteristics

The effects of anabolic implant on growth, carcass characteristics, and serum hormones were examined in 30 young bulls and steers fed a growing diet then a finishing diet. In a 2 X 3 factorial arrangement, steers and bulls received an implant of trenbolone acetate (TBA), TBA and estradiol-17 beta (E2), or no implant. Blood samples were taken serially (every 20 min for 6 h) at intervals during the growing and finishing phases. Percentage of DM, fat, protein, and ash and Warner-Bratzler shear test were measured and taste panel evaluations of the 9-10-11 rib section were obtained. Treatment with TBA and E2 increased weight gain in steers but not in bulls. There were no differences in feed efficiency, serum growth hormone (GH), and cortisol concentrations between bulls and steers or between treated groups and controls in bulls or steers, although during the finishing phase mean GH concentrations in treated steers were twofold higher than in controls and were similar to those in the bull groups. Serum insulin-like growth factor-I (IGF-I) increased twofold during the growing phase, then remained at that level. Steers implanted with TBA and E2, which had the highest gains among the steer groups, had the highest serum GH and IGF-I. Longissimus steaks from bulls treated with TBA alone or TBA and E2 were comparable to steaks from steers in the shear test. Taste panelists found steaks from TBA- and E2-treated bulls to be similar in tenderness and connective tissue to steaks from steers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of anabolic implants on beef intramuscular lipid content.

Sixty ribeye steaks were used to determine the effects of anabolic implants on i.m. lipid composition of beef steers. Steaks were obtained from carcasses (346 kg) of steers assigned to four treatment groups (C = nonimplanted control; ET = 28 mg of estradiol benzoate plus 200 mg of trenbolone acetate on d 0; ET/ET = ET on d 0 and d 61; and S/ET = 20 mg of estradiol benzoate plus 200 mg of progesterone on d 0 and ET on d 61) and fed a high-concentrate diet for 127 d. Total fatty acid content of the longissimus was less (P < .05) for implanted steers. Implanting increased (P < .05) stearic and linolenic acid percentages and reduced (P < .05) oleic acid percentage but did not alter (P > .05) percentages of other fatty acids. These changes translated into increased (P < .05) percentages of saturated fatty acids and reduced (P < .05) monounsaturated fatty acids in the longissimus of implanted steers. However, on a per-steak weight basis, implanting did not alter (P > .05) the amounts of any of the individual fatty acids, but it increased (P < .05) the total cholesterol amount. Implanting with an estrogenic compound first reduced (P < .05) the percentage and total amounts of linoleic and polyunsaturated fatty acids. On a percentage basis, implanting alters fatty acid amounts; however, when the increase in ribeye size with implanting is accounted for and fatty acids are evaluated on a per-steak basis, these differences are not significant.     

A RAL compound as an anabolic in cattle

Zeranol given alone has a medium level of activity in calves fed milk replacer, but a good to very good activity in bulls and steers. The effect on N retention of a combination of Zeranol (36 mg)+trenbolone acetate (140 mg) is of the level of the combination E2+TBA, which appears to be the better combination in cattle. The combination of Zeranol+trenbolone acetate seems to give more regular results in cattle of any age.     

Blood and serum components and organ weights in steers, bulls and zeranol-implanted bulls

To investigate certain physiological aspects of the mode of action of zeranol or Ralgro on growth, behavior and carcass quality of young bulls, concentrations of 19 blood components and weights of eight organs were determined. Experimental animals consisted of 36 untreated steers, 36 untreated bulls, 36 bulls implanted with zeranol at 3 mo of age and subsequently at 5, 8 and 10 mo and 36 bulls implanted with zeranol at 6 mo of age and subsequently at 9 and 11 mo. In addition, half of the animals in each group were subjected to moderate pre-slaughter stress (mixing and trucking 160 km); the other half was subjected to minimum pre-slaughter stress (no mixing and 4 km transport). Concentrations of cortisol, urea nitrogen and albumin in serum were higher (P less than .01) and those of glutamic oxaloacetic transaminase (GOT), lactate dehydrogenase (LDH), alkaline phosphatase (AP) and creatinine were lower (P less than .05) in steers than in intact males. Concentrations of GOT, LDH, and creatinine were higher (P less than .05) in implanted than those in control males. Pre-slaughter stress had a significant effect on several traits measured in blood or serum. Thyroid glands were smaller (P less than .01) in steers than in control and implanted males. Testes were smaller (P less than .01) in the zeranol-implanted than in untreated males. Results indicate that zeranol had only a minor effect on the 19 blood components studied, but it did reduce testicle size. Castration had a major impact on several of the blood components. Pre-slaughter management had a significant effect on several blood components.     

Growth, carcass and palatability traits of intact males and steers implanted with zeranol or estradiol early and throughout life

This study was conducted to assess the impact of implanting intact beef males with protein anabolic agents at varying intervals throughout life. Ninety-six intact males were assigned to three implant treatments: 1) not implanted, 2) implanted at 9 wk of age, weaning and at 56-d intervals thereafter with a 36-mg zeranol implant or 3) estradiol implant at 9 wk of age and 68 d post-weaning. During the 118-d, post-weaning growing period, eight animals per treatment (one replication) were castrated. After a 114-d finishing period, cattle were slaughtered (average age of 13 to 14 mo). Feedlot performance, carcass and palatability data were obtained. Average daily gains and feed efficiency did not differ (P greater than .05) between zeranol and estradiol-implanted intact males. Regardless of implant treatment, steers had lighter carcass weights (P less than .05) and higher (P less than .01) quality grades than intact males. Implanting either intact males or steers with zeranol or estradiol resulted in higher (P less than .05) numerical yield grades. Quality grades were higher in zeranol-implanted cattle than the non-implanted or estradiol-implanted cattle. Intact males implanted with zeranol were similar in carcass fatness to zeranol-implanted steers. No differences (P greater than .05) in tenderness or connective tissue were detected. Implanting intact males early and throughout life with zeranol made them similar to steers in fatness, while estradiol implantation had few effects on carcass and palatability traits of intact males or steers.     

Effects of a growth hormone-releasing factor analogue and an estradiol-trenbolone acetate implant on somatotropin, insulin-like growth factor I, and metabolite profiles in growing Hereford steers.

Hereford steers (290 +/- 6 kg of BW) were implanted (n = 4) with 140 mg of trenbolone acetate (TBA) and 28 mg of estradiol-17 beta (E2 beta) or nonimplanted (controls, n = 4). In Trial 1, effects of a single i.v. injection of 0, 20, 40, or 80 micrograms of a growth hormone-releasing factor (1-29 NH2) analogue (GRFa) on release of endogenous somatotropin (ST) were evaluated in a double 4 x 4 Latin square design. Plasma samples (n = 21) were obtained from -20 to 240 min after GRFa injection. Area under the ST response curve (AUC) increased (P = .009) in a dose-dependent manner (.2, 2.6, 3.6, 4.3 mg.min-1.mL-1, respectively). Mean ST concentration was not affected (P = .238) by implant but AUC was greater (P = .009) in implanted than in control steers. There was no interaction (P = .460) between dose of GRFa and presence of implant. In Trial 2, 80 micrograms of GRFa was administered at 12-h intervals to the same eight steers. Response of ST (AUC) to the first and last (13th) i.v. injection of GRFa was similar and not affected by implant. Before GRFa administration, plasma insulin-like growth factor I (IGF-I) concentrations were greater (P = .039) in implanted than in control steers (272 vs 164 ng/mL). Administration of GRFa increased plasma IGF-I (P = .0001), decreased plasma urea N (PUN) (P = .0001), and did not alter plasma glucose (P = .447) in both control and implanted steers. Data indicate that effects of GRFa and TBA/E2 beta on plasma IGF-I and PUN concentrations were additive in this study.     

Effects of implant regimens (trenbolone acetate-estradiol administered alone or in combination with zeranol) and vitamin D3 on fresh beef color and quality

In the first oftwo experiments, 123 calf-fed steers were used over a 2-yr period to evaluate the effects of trenbolone acetate (TBA)-based implants administered alone or in combination with zeranol implants on fresh beef muscle quality, color, and physiological maturity of the carcass. Implant treatments decreased (P < 0.05) a* values (d 0 and d 3 of retail display) and b* values (d 0, d 1, and d 3 of retail display) after 14 d of aging. Carcasses from cattle initially implanted with Revalor-S and reimplanted with Revalor-S on d 60 of the finishing period showed increased lean and bone maturity scores and ash content of the 9th to 11th thoracic buttons and Warner-Bratzler shear force values (WBS) compared to those initially implanted with Ralgro and subsequently reimplanted with Revalor-S or control cattle. In addition, implants decreased (P < 0.05) marbling, percentage of the carcasses grading Choice, and kidney, pelvic, and heart fat (KPH). Implant treatments increased (P < 0.05) ADG, hot carcass weights, and longissimus muscle (LM) area. In the second experiment over a 2-yr period, 166 steers fed as yearlings were allotted to one of two implant treatments and one of two vitamin D3 preharvest supplementation treatments. Implanted steers had heavier (P < 0.05) final body weights and higher (P < 0.05) ADG, less (P < 0.05) KPH fat, and larger (P < 0.05) LM. Also, implanted steers had more (P < 0.05) advanced bone maturity scores, higher (P < 0.05) ash content of the 9th to 11th thoracic buttons, and higher (P < 0.05) WBS values on 5-d postmortem loin steaks. Vitamin D3 feeding decreased (P < 0.05) final live weight, ADG (P < 0.05), and LM (P < 0.05), but did not significantly improve WBS values. In Experiment 2, neither implant treatment nor vitamin D3 supplementation had significant effects on L*, a*, or b* values of muscles in steaks before or during simulated retail display.     

Growth and carcass traits of heifers as affected by hormonal treatment

Seventy-seven heifers weighing about 200 kg were assigned randomly to intact control (C), ovariectomized (OVX) immunized against estradiol (BSA-E), BSA-E + trenbolone acetate (BSA-E + TBA), TBA or ovx + TBA groups. The objective of the study was to determine the effects of ovariectomy, immunoneutralization of estradiol and trenbolone acetate treatment on growth rate and carcass merit. Heifers were fed a corn-corn silage diet and were slaughtered when treatment groups attained live-animal weights of 433 kg. Observations of rate of growth, efficiency of feed conversion, characteristics of carcasses and characteristics of organoleptic properties of the cooked meat were made. Average daily gains (ADG) were similar in the control and OVX groups and tended to be less than in other treatment groups (P less than .36). Although not statistically significant, the observed mean for the BSA-E + TBA treatment suggests improved ADG and TDN per unit of gain, indicating a possible immunization X TBA interaction. Data also suggested that heifers implanted with TBA had increased ADG and efficiencies of gain. Possibly, immunoneutralization of endogenous estradiol can improve ADG as compared with control and OVX groups. Treatments had no effect on color or texture of lean muscle at the 12th rib interface. The OVX + TBA group had less (P less than .01) 12th rib fat cover than other groups and lower percent fat in the rib than C. The BSA-E + TBA and TBA groups also possessed larger (P less than .02) longissimus muscle areas than the control group. Observations of juiciness, tenderness and flavor were similar among all treatments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Implant sequence effects in intact male Holstein veal calves: live and slaughter traits

Seven sequences of growth promotant implants were used in special-fed intact male Holstein veal calves (n = 443). Calves received implants 4 d after arrival at the veal barn, 42, and 84. The following implants were used: placebo (0), Z (36 mg zeranol), ET (20 mg estradiol, 200 mg testosterone), EP/2 (10 mg estradiol, 100 mg progesterone), EP (20 mg estradiol, 200 mg progesterone), and EBA (24 mg estradiol, 120 mg trenbolone acetate). The following sequences were compared: 0-0-0 (negative control), 0-ET-ET, Z-ET-ET, 0-EP-EP, Z-EP-EP, 0-EP/2-EBA, and Z-0-EBA. From 0 to 42 d, Z implants increased (P<.05) ADG by 3.4% compared to placebo. However, implant schemes without an initial Z implant (0-ET-ET and 0-EP-EP) had higher (P<.05) mean ADG for the period from d 42 to 84. From 84 d to the end of the experiment, only the 0-EP/2-EBA treatment increased (P<.05) ADG compared to 0-0-0. Over the entire trial 0-ET-ET, 0-EP-EP, Z-EP-EP, and 0-EP/2-EBA implant sequences increased (P<.05) ADG by 3.2, 3.2, 2.4, and 4.7%, respectively, compared to the 0-0-0 sequence. Blood traits measured within 2 wk before slaughter were not affected by implant sequence, except that sequences with EP had higher (P<.05) leukocyte counts than were observed for the other sequences. Testicular weight was less (P<.01) for all of the implant sequences than for the negative control and less (P<.05) for Z-ET-ET than for 0-ET-ET, 0-EP-EP, 0-EP/2-EBA, and Z-0-EBA. The type and frequency of medical treatments did not differ among implant sequences for any of the 42-d phases, or over the entire trial. Generally, the growth promotant implants currently approved for beef cattle resulted in approximately 50% of the increase in growth rate in Holstein intact bull calves, as has been observed in beef-type steers or heifers.