estradiol-benzoate--progesterone-drug-combination and Weight-Gain

An 84-d grazing experiment was conducted in 2 growing seasons to evaluate interactions of stocking rate and steroidal implants with BW gain and symptoms of toxicosis in yearling steers grazing endemic endophyte-infected (E+) tall fescue (Festuca arundinacea Schreb.). A 4 x 2 factoral design was used to evaluate 4 stocking rates (3.0, 4.0, 5.0, and 6.0 steers/ ha) with or without steroidal implants (200 mg of progesterone + 20 mg of estradiol benzoate). Treatment combinations were randomly assigned to eight 1-ha pastures of E+ Kentucky-31 tall fescue (i.e., treatments were not replicated). Treatment effects were analyzed for ADG, total BW gain per hectare, forage availability, and hair coat ratings. At the conclusion of grazing in the second year (22 June), steers were placed on a bermudagrass [Cynodon dactylon (L.) Pers.] pasture, and rectal temperatures and serum prolactin concentrations were monitored for 10 d to assess carryover effects of stocking rate and steroidal implants on recovery from toxicosis-related heat stress. Forage availability differed (P < 0.001) between years, but there were no year x treatment interactions (P > 0.10). There was an implant x stocking rate interaction (P < 0.05) on ADG. Differences between the slopes in the regression equations indicated that ADG responded to implantation when stocking rates were low, but the response diminished as stocking rate increased. Stocking rate did not influence (P = 0.89) postgraze rectal temperature, but the regression intercept for implanted steers was 0.4 degrees C greater (P < 0.05) than for nonimplanted steers, and the difference was consistent across the entire 10-d fescue-free grazing period. Concentrations of prolactin increased during the 10-d fescue-free grazing period, but trends differed due to an implantation x stocking rate interaction (P < 0.05). Results indicate that implantation with progesterone + estradiol benzoate increases ADG with lower stocking rates, but the effect diminishes with increased grazing intensity. Implantation with steroid hormones increased rectal temperatures, but during a fescue-free grazing period rectal temperatures and serum prolactins for implanted and nonimplanted steers returned to values indicative of a stable and healthy status in a 192- to 240-h (i.e., an 8- to 10-d) period. However, because the treatments used in this study were not replicated, these observations need to be confirmed with replicated studies.

Topics: Absorbable Implants; Animal Husbandry; Animals; Body Temperature; Cattle; Climate; Drug Combinations; Estradiol; Male; Progesterone; Time Factors; Weight Gain

One hundred forty spring-born Angus x Gelbvieh and purebred Angus steers were selected for study as early weaned (EW; average age at weaning = 90 +/- 30 d) or traditionally weaned (TW; average age at weaning = 174 +/- 37 d) steers that were non-implanted or implanted (Synovex-S, Fort Dodge Animal Health, Overland Park, KS). Initially, steers were sorted by age, sire, and farm, and then allotted randomly in a 2 x 2 factorial arrangement of treatments of EW implanted (EWI), EW nonimplanted (EWN), TW implanted (TWI), or TW nonimplanted (TWN). Ultrasound measurements (US) of LM area (LMA), 12th rib fat thickness (US-BF), and marbling (US-M) were collected every 28 d during the time that steers were on feed. At 202 d of age, EW calves had larger US-LMA, US-BF, and BW than TW calves (37.9 vs. 32.3 cm2, 0.38 vs. 0.26 cm, and 271.6 vs. 218.9 kg, respectively; P < 0.001). At slaughter, EW calves had heavier HCW (290.4 vs. 279.7 kg, respectively; P < 0.05) and greater USDA marbling scores (51.25 vs. 46.26, respectively; P < 0.05) than TW calves; more EW steers graded USDA Choice or greater (P = 0.05). However, no differences were detected in BW (P = 0.15), LMA (P = 0.39), BF (P = 0.45), or liver abscess scores (P = 0.41). Twenty-four implanted steers were selected from the original group of 140 and sorted into two slaughter groups of 12. Twelve implanted steers from each weaning group, matched in slaughter BW but differing in age, were subsampled at slaughter to assess the effect of weaning age and chronological age on muscle tenderness. Younger animals had lower Warner-Bratzler shear force values (P < 0.001) than older calves after 14 d of postmortem aging; however, no differences were found in tenderness after 21 d of aging. Furthermore, there was greater variance (P < 0.001) in Warner-Bratzler shear force values among younger, EW steers vs. older, TW steers. These data provide evidence that early weaning of beef calves may be used as a tool to more effectively manage the cow-calf production system without compromising the quality of the offspring.

Topics: Aging; Animal Feed; Animal Husbandry; Animal Nutritional Physiological Phenomena; Animals; Body Composition; Cattle; Diet; Drug Combinations; Estradiol; Male; Meat; Progesterone; Weaning; Weight Gain

The separate and combined effects of Synovex-S (SYN) ear implants and thyroxine (T4)-5'-monodeiodinase inhibition (Trial 1) and T3 injection to create a mild elevation in circulating T3 concentrations (Trial 2) on BW gain and composition of gain were studied. Trial 1 used 24, 285-kg Angus steers in two experimental phases. Low-level feeding of propylthiouracil (PTU, 1.5 mg/kg BW daily) was used to achieve inhibition of T4-5'-monodeiodinase activity (TMA). Twelve steers received neither treatment (control) and 12 received SYN+PTU (hypothesized to maximize weight gain) from 0 to 56 d (phase 1) in a single factor treatment comparison. Subsequently, PTU was fed to six control steers and not fed to six of the original SYN+PTU steers from 56 to 175 d (phase 2) in a 2 x 2 arrangement of treatments. Trial 2 used 24, 302-kg Angus-Hereford steers. Treatments were without or with SYN and without or with sc injections of T3 in polyethylene glycol (2 micrograms/kg BW every 48 hr) in a 2 x 2 factorial arrangement of treatments. In both trials, all steers were individually fed a diet of a corn-based concentrate and silage mixture at an equal metabolizable energy intakes per unit of metabolic body weight (.25 Mcal/kg BW.75). Measurements of daily dry matter intakes, weekly BW, 28-d estimates of empty body components (measured by urea dilution), final TMA (trial 1) and plasma thyroid hormone concentrations were obtained. In both trials, SYN increased BW gain and protein accretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Body Composition; Cattle; Drug Combinations; Drug Implants; Estradiol; Male; Progesterone; Propylthiouracil; Thyroid Gland; Triiodothyronine; Weight Gain

Sixty-three Angus x Simmental calves were allotted to a bull or a steer group based on sire, birth date, and birth weight to determine effects of castration status on performance, carcass characteristics, and circulating insulin-like growth factor I (IGF-I) concentrations in early-weaned cattle. At 75 d of age, calves in the steer group were castrated. Calves were not creep-fed prior to weaning. All calves were weaned and weighed at an average age of 115 d and transported by truck to the OARDC feedlot in Wooster, OH. Performance and carcass characteristics were measured in three phases. Phase 1 was from 115 to 200 d of age, phase 2 was from 201 to 277 d of age, and phase 3 was from 278 d of age to slaughter. Before implantation, four bulls and four steers were selected for serial slaughter and carcass evaluation. Steers were implanted with Synovex-C at 130 d of age and with Revalor-S at 200 and 277 d of age. Serum samples were collected from all calves on the day of implantation, 28 and 42 d after implantation, and at slaughter and analyzed for circulating IGF-I concentration. Bulls gained 9.7% faster (1.75 vs 1.60 kg/d; P < 0.01), consumed 25 kg more DM (521 vs 496 kg; P = 0.11), and were 3.3% more efficient (282 vs 273 g/kg, P < 0.10) than steers in phase 1. However, steers gained 10.5% faster (1.62 vs 1.46 kg/d; P < 0.02), consumed similar amounts of DM, and were 6.5% more efficient than bulls (214 vs 201 g/kg; P < 0.06) in phase 2. Overall gains and efficiency were similar between bulls and steers; however, bulls consumed 140 kg more DM (P < 0.05), were 27 kg heavier (P < 0.05), and had to stay in the feedlot 18 more days (P < 0.05) than steers to achieve a similar amount of fat thickness. Implanted steers had greater concentrations of circulating IGF-I than bulls (P < 0.01), and the pattern of IGF-I concentration over time was affected by castration status (castration status x time interaction; P < 0.01). Synovex-C had a lower impact on circulating IGF-I concentration (implant effect, P < 0.01) than either Revalor-S implant. Eighty-five percent of both bulls and steers had marbling scores sufficient to grade low Choice or better. Bulls achieved their target fat thickness later, increased muscle growth, and deposited fat more favorably than steers, possibly due to a gradual increase in IGF-I concentration as the testicles grew rather than the large fluctuations in IGF-I concentration observed in steers following implantation.

Topics: Age Factors; Anabolic Agents; Animals; Body Composition; Cattle; Drug Combinations; Estradiol; Insulin-Like Growth Factor I; Male; Meat; Orchiectomy; Progesterone; Trenbolone Acetate; Weaning; Weight Gain

The objective of two experiments was to correlate plasma levels of urea N (PUN) and the percentage of urine N in the form of urea (UUN) to weight gain in response to different dietary protein regimens for growing Angus steers. In Exp. 1, 60 steers (302 kg BW) were assigned to various levels of dietary N (control plus supplemental N to provide from 100 to 400 g more crude protein daily) within two sources of supplemental N (soybean meal [SBM] or a mixture of two parts corn gluten meal:one part blood meal [CGM:BM]). In Exp. 2, 27 steers (229 kg BW) were fed two levels of SBM, and half of the steers received growth-promoting implants. Steers were housed in groups of 12 and fed individually for 84 d in both experiments. Corn silage was fed at a restricted rate to minimize orts. Jugular blood and urine samples were collected during the experiments. In Exp. 1, maximal ADG of steers fed SBM (1.0 kg) was reached with 671 g/d total crude protein, or 531 g/d metabolizable protein. Maximal ADG of steers fed CGM:BM (0.91 kg) was reached with 589 g/d total crude protein, or 539 g/d metabolizable protein. The DMI was higher (P < 0.07) for steers fed SBM (6.37 kg/d) than for steers fed CGM:BM (6.14 kg/d). Increasing ruminal escape protein from 36% (SBM) to 65% (CGM:BM) of CP decreased (P < 0.05) endogenous production of urea, as evidenced by lower concentrations of urea in blood and lower UUN. In Exp. 2, increasing supplemental protein from 100 to 200 g/d increased (P < 0.05) ADG and PUN. Implants lowered (P < 0.05) UUN, particularly at the higher level of supplemental protein. Protein supplementation of growing steers can be managed to maintain acceptable ADG yet decrease excretion of urea in the urine.

Topics: Ammonia; Animal Feed; Animals; Cattle; Dietary Proteins; Drug Combinations; Estradiol; Fatty Acids, Volatile; Gastrointestinal Contents; Least-Squares Analysis; Linear Models; Male; Nitrogen; Progesterone; Random Allocation; Rumen; Silage; Urea; Weight Gain

One hundred forty-three Angus x Simmental crossbred steers (initial BW = 155.1 +/- 4.5 kg) were used in a 2-yr study (yr 1, n = 67; yr 2, n = 76) to determine the effects of weaning age, implant regimen, and the weaning age x implant regimen interaction on steer growth and performance, organ mass, carcass characteristics, and cooked beef palatability. Steers were early-weaned at an average age of 108 d (EW) or normally weaned at an average age of 202 d (NW) and allotted by weight to an aggressive or nonaggressive implant regimen. On their respective weaning dates, EW and NW steers were penned individually and fed a grain-based diet until they were slaughtered at a final BW of 546 kg. A subsample of steers (n = 2 per treatment) were slaughtered at 254 kg. At 254 kg, EW steers implanted with the aggressive implant regimen had 64% greater backfat depth than those implanted with the nonaggressive implant regimen; conversely, NW steers implanted with the aggressive implant regimen had 52% lower backfat depth than those implanted with the nonaggressive implant regimen (weaning status x implant regimen interaction; P < 0.01). A similar interaction was observed for empty visceral organ weights. Early-weaned steers were younger (354.7 vs 372.4 d; P < 0.01) at final slaughter but were in the feedlot longer (246.5 vs 169.6 d; P < 0.01) than NW steers, whereas the aggressive implant regimen decreased days fed (203.3 vs 212.7; P < 0.07) compared to the nonaggressive implant regimen. Overall ADG was greater for EW than for NW steers (1.61 vs 1.50 kg/d; P < 0.01) and for the aggressive compared with the nonaggressive implant regimen (1.59 vs 1.52 kg/d; P < 0.02). Early-weaned steers consumed less DM per day (7.4 vs 8.5 kg/d; P < 0.01) and were more efficient (0.217 vs 0.208 kg/kg; P < 0.02) but consumed more total DM (1,817 vs 1,429 kg; P < 0.01) than NW steers while in the feedlot. Implant regimen did not affect DMI (P > 0.37) or feed efficiency (P > 0.15). Weaning status did not affect carcass characteristics (P > 0.14), final empty body composition (P > 0.25), or final longissimus muscle composition (P > 0.18); however, steaks from EW steers had higher (P < 0.05) taste panel tenderness and juiciness ratings than steaks from NW steers. The aggressive implant regimen decreased yield grade (P < 0.02), but did not affect quality grade (P > 0.86) compared to the nonaggressive implant regimen. Placing early-weaned steers on an aggressive implant regimen is a viable managem

Topics: Age Factors; Anabolic Agents; Animals; Body Composition; Cattle; Delayed-Action Preparations; Drug Combinations; Estradiol; Male; Progesterone; Trenbolone Acetate; Weaning; Weight Gain

In a 172-d finishing trial (Exp. 1), 210 recently weaned crossbred heifers were allotted to six growth promotant treatment groups, involving implanting initially with Synovex-C (C) or H (H) followed by reimplanting with Finaplix-H (F) or H and F. Melengestrol acetate (MGA) was provided in the diet to four of the treatment groups. Heifers fed MGA and administered only F as the terminal implant had the greatest (P = .01) number of mature ovaries with follicles but also had lower (P = .01) gain/DMI. In a 182-d finishing study (Exp. 2), 270 recently weaned crossbred heifers were allotted to the following six implant (d 0)/ reimplant (d 70) groups using no implant (N), Ralgro (R) or H: N/R, R/H, R/R, N/R, H/H and R/R for Treatments 1 through 6, respectively. On d 70, all heifers were implanted with F. Heifers were fed MGA from d 70 to 182 (Treatments 1, 2, and 3) or for the entire trial (Treatments 4, 5, and 6). Implanting on d 0 increased (P < .05) overall ADG. Differences (P > .05) in performance were not found between MGA treatment groups. Using an H implant/reimplant regimen decreased (P = .01) ovarian and(or) follicular development when compared with an R implant/reimplant regimen. In a 126-d finishing trial (Exp. 3), 360 crossbred yearling heifers were used to evaluate F and estrogen (Implus-H) implants when used in combination with an MGA feeding program. Heifers receiving only F in combination with MGA had greater (P < .05) ADG, whereas all heifers fed MGA had greater (P < .05) gain/DMI than heifers not fed MGA. These data suggest that feeding MGA was not beneficial for young heifers, particularly if they are provided an initial estrogenic implant followed by a second implant. In older (yearling) heifers, increased gains and gain/DMI were obtained by feeding MGA and implanting initially or 56 d later with F.

Topics: Animal Feed; Animal Husbandry; Animals; Cattle; Delayed-Action Preparations; Drug Combinations; Energy Intake; Estradiol; Female; Melengestrol Acetate; Ovary; Progesterone; Progesterone Congeners; Testosterone; Vaccination; Weight Gain

We assessed testis function, aggressive behavior, and carcass traits in beef bulls actively immunized against GnRH at 1, 4, or 6 mo of age. In addition, we examined the effect of combining immunization with insertion of estrogen-containing implants (Synovex C) at 1 mo of age. Unimmunized bulls and steers were included as control animals. All immunized calves received a secondary immunization at 12 mo of age. Anti-GnRH titer was evident at slaughter in all immunized animals. Neither age at primary immunization nor implant status affected (P > .05) anti-GnRH titer at slaughter. Immunization, but not implant status, reduced (P < .05) serum concentration of testosterone and testis weight at slaughter. The final live weight and feedlot gain of immunized and unimmunized bulls were comparable (P > .05). In contrast, aggressive behavior was reduced (P < .05) and carcass quality was improved (P < .05) by immunization. These data suggest that active immunization against GnRH is a practical, noninvasive alternative to physical castration in the management of bull calves.

Topics: Aggression; Animals; Antibodies; Behavior, Animal; Cattle; Drug Combinations; Drug Implants; Estradiol; Gonadotropin-Releasing Hormone; Immunization, Secondary; Male; Meat; Progesterone; Testis; Testosterone; Vaccination; Weight Gain

The influence of Synovex-S (SYN) ear implant (200 mg progesterone and 20 mg estradiol benzoate) and Somavubove (SbV) recombinant bovine growth hormone (.1 mg/kg BW i.m., daily) on live animal performance, tissue growth, and the partitioning of energy gain was determined using a slaughter-balance protocol with 25 young MARC II x (Angus-Hereford crossbred) beef steers (initial BW 182 +/- 1.8 kg). Following 21 d of adjustment to individual pens and to a diet of 80% concentrate and 20% corn-grass (1:1) silages, five groups of five steers per group were assigned to initial slaughter or a 2 x 2 factorial arrangement of treatments of CTL (no implant + daily placebo i.m. injection of bicarbonate-saline), SYN (implant + placebo), SbV, or SYN + SbV and slaughtered at 56 d on treatment. Steers were fed (per kilogram BW.75 daily) 20 g of CP and 252 Kcal of ME and consumed 5.5 +/- .07 kg/d DM across treatments. Empty body and carcass gains were affected (SYN, P < .01; SbV, P < .01) by treatments (CTL, SYN, SbV, and SYN + SbV: 1.26, 1.43, 1.63, 1.78 kg/d, SEM = .05, and .78, .97, .97, 1.08 kg/d, SEM = .04, respectively). Noncarcass gain was .45, .48, .60, and .60 kg/d (SEM = .03; SbV, P < .01). For empty body, both protein and water gains were greater for SYN-implanted steers (P < .05) than for steers not implanted and for SbV-injected steers (P < .01) than for placebo-injected steers. Treatments did not influence the efficiency of energy gain. The proportional amount of energy deposited as protein was greater (P < .01) for SbV-injected steers than for placebo-injected steers. The proportional amount of protein deposited was not influenced by SYN (P > .10); however, means were numerically greater for SYN-implanted steers than for steers not implanted, the largest mean being for the SYN + SbV treatment group. Somavubove increased (P < .01) the efficiency of energy deposited as protein in both the empty body and carcass compared with steers not receiving SbV. Efficiency of energy deposited as protein in the empty body tended to be greater (P < .10) for SYN-implanted steers than for steers not implanted. The efficiency with which total feed energy was deposited as protein in empty body was 10% greater for the SYN group than for the CTL group, 21% greater for the SbV group than for the CTL group, and 37% greater for the combined SYN + SbV treatment than for the CTL group. The data from this study are interpreted to indicate that SYN and SbV act in an additive manner to imp

Topics: Animals; Body Composition; Body Weight; Cattle; Drug Combinations; Estradiol; Growth Hormone; Male; Progesterone; Random Allocation; Recombinant Proteins; Weight Gain

Forty-two heifers and 38 steers sired by either Charolais (n = 47) or Salers (n = 33) from Bos indicus x Hereford dams were used to determine the effects of an anabolic agent on metacarpal characteristics and accompanying weight gain and carcass characteristics. Calves were blocked by sex and sire breed and either not implanted or implanted with Synovex-C within 45 d of birth, and with Synovex-S or -H at weaning and 84 and 169 d postweaning. Calves grazed oat pastures immediately after weaning for 169 d, after which calves received a feedlot diet for 124 d and were slaughtered. Live weight and hip height were recorded at initial implanting, weaning, d 84 and d 169 postweaning, and at approximately 28-d intervals during the feedlot period. Metacarpal and carcass characteristics were determined after slaughter. Metacarpals from implanted calves had greater medio-lateral axis (P < .01), cortical areas (P < .05), and cross-sectional areas (P < .05) and tended to have a greater breaking load (P < .08) than bones from nonimplanted calves. Implanted steers had shorter (P < .05) metacarpals than nonimplanted steers. Implanted calves had a greater (P < .05) ADG to weaning and over the postweaning grazing and feedlot periods than control calves. The implant did not alter backfat thickness but decreased (P < .05) percentage of kidney, pelvic, and heart fat and quality grade and tended (P < .07) to improve yield grade in heifers, but not in steers. Implanted calves tended (P < .08) to have a lower marbling score.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Aging; Animals; Body Composition; Bone Development; Cattle; Drug Combinations; Drug Implants; Estradiol; Female; Least-Squares Analysis; Male; Metacarpus; Progesterone; Weight Gain

Studies were conducted to evaluate the effects of delayed implanting or the use of a low-dose implant followed by a higher-dose implant in feedlot cattle. In the first study, 150 steers were allotted to 15 pens (three pens/treatment) and assigned to a nonimplant treatment (control), a single zeranol (36 mg) implant (R), or a double zeranol implant (DR) administered at the start of a 140-d finishing period, or a single zeranol implant administered at the start of an 80-d growing period, followed by a single (RR) or double (RDR) zeranol implant administered at the start of the finishing period. Steers managed under the DR, RR, and RDR implant schemes had greater (P < .10) finishing period gains and intakes than the control steer group. However, only DR and RDR steer groups had improved (P < .10) finishing period feed conversions compared with control steers. In combined growing and finishing periods, the RDR steer group displayed the lowest (P = .12) feed:gain ratio. In a second trial, conducted concurrently to the zeranol trial, steers that did not receive an initial implant containing 20 mg of estradiol benzoate plus 200 mg of progesterone (S) but were subsequently implanted twice, once at the start of the finishing period and again 80 d later, had a lower (P < .11) finishing period feed:gain ratio (6.08 vs 6.51) than steers implanted all three times.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adipose Tissue; Animal Nutritional Physiological Phenomena; Animals; Cattle; Dose-Response Relationship, Drug; Drug Combinations; Drug Implants; Eating; Estradiol; Male; Meat; Progesterone; Random Allocation; Time Factors; Weight Gain; Zeranol

Two trials were conducted to evaluate effects of Synovex C implants on replacement heifers, given at two different ages. Crossbred heifer calves (n = 370) were allotted to four treatments: 1) nonimplanted controls, 2) implanted at 2 mo, 3) implanted at 6 mo, and 4) implanted at both 2 and 6 mo of age. Heifers implanted at 2 mo gained 7 kg more (P = .01) by 6 mo than those not implanted at 2 mo. No differences were found in 22-mo weights. All implanted heifers had larger (P = .01) yearling pelvic area than controls. All heifers implanted at 6 mo continued to have larger (P = .01) pelvic area at 22 mo. All implanted heifers had higher (P = .05) occurrence of non-ovulatory estrus. No differences were found among treatments in percentage of heifers puberal before breeding, in estrus first 21 d of breeding, or in first-service conception rate. In only one trial, pregnancy first 21 d and total pregnancy in 63-d breeding season were decreased (P = .05) by implanting at 6 mo. At subsequent calving, an interaction existed between the effects of the 2- and the 6-mo implant for calf birth weight and pelvic area:birth weight ratio. A single implant at either 2 or 6 mo decreased (P = .01) calving difficulty score; and implanting at both 2 and 6 mo showed the greatest reduction in calving difficulty. Implants had no significant long-term effects on reproduction or calf production of 2-yr-old cows.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Birth Weight; Cattle; Cattle Diseases; Drug Combinations; Drug Implants; Dystocia; Estradiol; Female; Fertility; Mammary Glands, Animal; Ovary; Pelvic Bones; Pelvimetry; Pregnancy; Progesterone; Random Allocation; Reproduction; Sexual Maturation; Time Factors; Weight Gain

This experiment examined the effect of daily administration of 3,5,3'-triiodothyronine (T3) on plasma profiles of T3, thyroxine (T4), 3,3',5'-triiodothyronine (reverse T3; rT3) and thyrotropin (TSH) in beef steers in which protein accretion was increased by using implants of Synovex-S (SYN). Twenty-four Angus-Hereford steers (302 +/- 16 kg) were individually fed a diet of a corn-based concentrate and silage mixture for 56 d at equal energy intake per steer (ME/unit BW.75). A 2 x 2 factorial arrangement of treatments was used in which treatments were SYN ear implants (200 mg of progesterone and 20 mg of estradiol benzoate) or no implants and s.c. injections of T3 in polyethylene glycol (2 micrograms of T3/kg BW every 48 h) or no injections of T3. Blood samples were collected every 2 wk. Plasma T3 concentration during the experimental period was increased in T3-treated steers (3.0 +/- .1 vs 2.2 +/- .1 ng/mL, P < .01) and was decreased in SYN-implanted steers (2.4 +/- .1 vs 2.7 +/- .1 ng/mL, P < .01). Plasma T4 and rT3 concentrations were reduced (22 +/- 4 vs 75 +/- 2 and .04 +/- .01 vs .12 +/- .01 ng/mL, respectively, P < .01) in T3-treated steers. Concurrently, plasma TSH concentration was decreased in T3-treated steers (.37 +/- .01 vs .51 +/- .02 ng/mL, P < .02). Synovex-S increased BW gain (21.0%, P < .01) and protein gain (35.6%, P < .01) compared with that of nonimplanted steers. Body weight gain and protein gain were not affected by treatment with T3.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Cattle; Drug Combinations; Drug Implants; Drug Interactions; Estradiol; Injections, Subcutaneous; Male; Progesterone; Thyroid Hormones; Thyrotropin; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse; Weight Gain

Effects of diethylstilbestrol (DES, 10 mg/d orally, Trial 1) or Synovex-S (SYN, 220 mg ear implant, Trial 2) on gain and N balance (g/d) were determined in steers that consumed 1.3, 2.7, 4.4 and 7.4 kg DM/d (Trial 1) and 1.3, 2.9, 4.3 and 6.6 kg DM/d (Trial 2). Each trial was a replicated 4 x 4 Latin square with four pairs of steers per trial (BW:322 kg, Trial 1; 278 kg Trial 2) and a control and growth promoter steer in each pair. Steers were fed a pelleted 75% concentrate diet containing 16.7% (DM basis). Each period consisted of 1 wk of intake adaptation, 5 wk of feeding and 1 wk in metabolism crates (2-d adjustment and 5-d collection). Steers were switched among DMI but not among promoter treatments. Intercept and slope, respectively, for the regression of BW gain (kg/d) on DMI (kg/d) were -.66 and .276 for control vs -.84 and .328 for DES steers and -.69 and .276 for control vs -.89 and .356 for SYN steers. Similar regression values for N balance (g/d) on DMI (kg/d) were -10.3 and 6.91 for control vs -17.2 and 9.10 for DES steers and -4.5 and 4.67 for control vs -7.6 and 5.85 for SYN steers. Across trials, slopes differed from zero (P less than .01), and promoter slopes differed from controls for gain (P less than .01) and N balance (P less than .10). During an extra period at the end of each trial, all steers were fed the high intake level for 6 wk, followed by N balance determinations the last 3 d of a 7-d fast.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animal Feed; Animals; Cattle; Dietary Proteins; Diethylstilbestrol; Digestion; Drug Combinations; Estradiol; Male; Nitrogen; Progesterone; Regression Analysis; Weight Gain

Ninety crossbred beef heifers averaging 260 kg were blocked by weight and allotted randomly to 15 pens of six heifers each, with three replicates per treatment. The treatments were spayed heifers (S); intact heifers (I); S + Synovex-H7 (SH); I + Synovex-H (IH); and S + Synovex-S7 (SS). The heifers were spayed vaginally with a Willis instrument; intact heifers were rectally palpated for reproductive soundness. Heifers were fed a growing diet (55 d), re-implanted and subsequently fed a finishing ration (73 or 101 d). All heifers were observed for estrus daily at approximately 0600 and 2000 until d 69. A jugular vein blood sample was obtained from each heifer on d 48, 55, 62 and 69 for blood progesterone analysis. Results of blood progesterone analysis and reproductive tract examination indicated that two spayed heifers were incompletely spayed, a 96% success rate. The SH and SS heifers continued to exhibit estrous behavior despite being successfully spayed. Heifers implanted with Synovex-H had greater (P less than .01) ADG and were more efficient (P less than .03) than nonimplanted heifers. The SS heifers had greater ADG (P less than .05) during the finishing phase than SH heifers, but no advantage of SS over SH was apparent during the growing phase. The overall ADG response to implantation was fourfold greater (P less than .07) in the spayed heifers than in the intact heifers (32 vs 8%). Heifers implanted with Synovex-H had greater adjusted hot carcass weight (P less than .02) and ribeye area (P less than .002) than nonimplanted heifers. For adjusted live weight and ribeye area, the response to implantation was approximately threefold greater in the spayed heifer than the intact heifer. These results demonstrate that spaying and implanting heifers can increase rates and efficiency of gain even though behavioral estrus is not eliminated.

Topics: Animals; Body Composition; Cattle; Drug Combinations; Drug Implants; Estradiol; Female; Linear Models; Ovariectomy; Progesterone; Random Allocation; Testosterone; Weight Gain

The effects of anabolic implants, growth phase (growing vs finishing) and rate of growth on the priorities for protein and fat deposition were determined in yearling cattle. Santa Gertrudis crossbred yearling steers weighing 290 kg were individually fed diets varying in forage and grain content and either not implanted (n = 16) or implanted (90-d intervals) with Ralgro (n = 13) or Synovex-S (n = 12) implants. The cattle were fed toward a similar expected final empty BW (455 kg). Initial and interim empty body composition was measured via deuterium oxide dilution; final composition was determined by carcass specific gravity. During a 100-d growing phase, rates of protein gain were increased (P less than .12) to 118 and 131 g/d from 98 g/d for Ralgro and Synovex vs nonimplanted cattle, respectively. Concurrently, the fraction of protein in empty body growth was increased (P less than .09) from 17.5% for controls to 23.8 and 19.7% for Ralgro- and Synovex-implanted steers, respectively. This change in protein growth occurred concomitant with mobilization of fat and a reduction (P less than .04) in fat gain with Ralgro and Synovex implants. During the 136-d finishing phase, protein accretion was 115 and 132 vs 93 g/d for Ralgro- and Synovex-implanted cattle vs nonimplanted cattle; this represented a 24 and 42% increase (P less than .03) with Ralgro and Synovex, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adipose Tissue; Anabolic Agents; Animals; Body Composition; Cattle; Drug Combinations; Drug Implants; Estradiol; Lipid Metabolism; Male; Progesterone; Proteins; Random Allocation; Regression Analysis; Weight Gain; Zeranol