Anabolic Implants Varying in Hormone Type and Concentration Influence Performance, Feeding Behavior, Carcass Characteristics, Plasma Trace Mineral Concentrations, and Liver Trace Mineral Concentrations of Angus Sired Steers

Fifty Angus-sired steers were utilized to evaluate the effects of anabolic implants varying in hormone type and concentration on performance, carcass traits, and plasma and liver trace mineral concentrations over 129 d. Steers were stratified by weight into one of four (n = 12 or 13/treatment) implant treatments: (1) estradiol (E2; 25.7 mg E2; Compudose, Elanco Animal Health, Greenfield, IN, USA), (2) trenbolone acetate (TBA; 200 mg TBA; Finaplix-H, Merck Animal Health, Madison, NJ, USA), (3) combination implant (ETBA; 120 mg TBA + 24 mg E2; Revalor-S, Merck Animal Health), or (4) no implant (CON). Steers were randomly assigned to pens equipped with GrowSafe bunks and fed a corn and barley-based finishing ration. Overall average daily gain and body weight were greater for ETBA and TBA than CON (p ≤ 0.04), but not E2 (p ≥ 0.12). Feed efficiency and hot carcass weight were only greater than CON for ETBA (p ≤ 0.03). Plasma and d 2 liver Zn concentrations were lesser for ETBA than CON (p ≤ 0.01) and d 10 liver Mn was lesser (p = 0.0003) for TBA than CON. These data indicate that implants containing TBA influence growth and trace mineral parameters, though more work investigating this relationship is necessary.

The Impact of Polyamine Precursors, Polyamines, and Steroid Hormones on Temporal Messenger RNA Abundance in Bovine Satellite Cells Induced to Differentiate

Emerging research suggests that hormones found in anabolic implants interact with polyamine biosynthesis. The objective of this study was to determine the effects of steroidal hormones, polyamines and polyamine precursors on bovine satellite cell (BSC) differentiation and polyamine biosynthesis temporally. Primary BSCs were induced to differentiate in 3% horse serum (CON) and treated with 10 nM trenbolone acetate (TBA), 10 nM estradiol (E2), 10 nM TBA and 10 nM E2, 10 mM methionine, 8 mM ornithine, 2 mM putrescine, 1.5 mM spermidine, or 0.5 mM spermine. Total mRNA was isolated 0, 2, 4, 8, 12, 24, and 48 h post-treatment. Abundance of mRNA for genes associated with induction of BSC differentiation: paired box transcription factor 7, myogenic factor 5, and myogenic differentiation factor 1 and genes in the polyamine biosynthesis pathway: ornithine decarboxylase and S-adenosylmethionine—were analyzed. Overall, steroidal hormones did not impact (p > 0.05) mRNA abundance of genes involved in BSC differentiation, but did alter (p = 0.04) abundance of genes involved in polyamine biosynthesis. Polyamine precursors influenced (p < 0.05) mRNA of genes involved in BSC differentiation. These results indicate that polyamine precursors and polyamines impact BSC differentiation and abundance of mRNA involved in polyamine biosynthesis, while steroidal hormones altered the mRNA involved in polyamine biosynthesis.

389 Interactions between zinc, copper, and growth promoting technologies in beef cattle

Trace minerals (TM) are required for many biochemical processes and support optimal animal growth. However, as animal genetics and feed technologies in the beef industry have advanced, our understanding of the TM requirements of modern cattle has lagged. Recently, Zn and Cu have emerged as potential targets for better understanding the interaction between nutrition and growth-promoting technologies like anabolic implants and β-agonists (BA). Both Zn and Cu are phosphodiesterase inhibitors, potentially maintaining cAMP concentrations, potentiating the BA signal. Zinc supplementation well above national recommendations can improve ADG or HCW in finishing cattle during the BA feeding period, and N retention is increased by both Zn and BA supplementation, suggesting a major role for Zn is in protein accretion. Interestingly, Cu status of feedlot steers appears to affect ADG during the BA period, where steers with moderate liver Cu and 10 mg Cu/kg diet DM gaining more than steers with high or low Cu status. Anabolic implants likely improve growth through altering protein deposition, degradation and satellite cell proliferation, processes that can be linked to Cu and Zn metalloproteins. Implanting cattle decreases both plasma and liver Zn, and heifers receiving a long-lasting implant had greater HCW when supplemented with 100 mg Zn/kg DM when compared with 30 mg Zn/kg DM. It is apparent Cu status and supplementation also affect the response to hormone implants. Steers supplemented with 20 mg Cu/kg DM had greater liver Cu concentrations and a lesser response to an implant than steers supplemented with 10 mg Cu/kg DM. Current state of knowledge suggests TM status and diet concentrations can impact the response to growth promoting technologies. Much remains to be learned about cattle requirements for dietary TM, and the appropriate TM concentrations to optimize feedlot cattle performance.

98 Comparing the effectiveness of anabolic implants in Santa Gertrudis sired steers versus Angus steers

This research compared the use of implants in Bos indicus influenced animals versus Bos taurus in a feedlot setting. Twenty steers were blocked by weight and breed in a 2 x 2 factorial design examining two different breeds: Angus (AN; n = 10) or Santa Gertrudis influenced (SGI; n = 10), and two implant strategies: no implant (CON; n = 10) or a combined implant (CI; n = 10). Steers were randomly placed into pens equipped with GrowSafe® bunks, fed the same ration, and weighed and ultrasounded on days 0, 28, 56, 84, and 112. Blood was collected on days 0, 2, 10, 28, 56, 84, and 112. Backfat measurements (BF), weights, and blood urea nitrogen (BUN) were determined. Data were analyzed using repeated measures and the ProcMixed procedure of SAS, looking at the main effects of breed, implant, and breed*implant. There were no initial differences (P &gt; 0.05) in weight between any of the main effects. The main effects of breed, implant, and breed*implant demonstrate that AN gained more (P &lt; 0.05) weight than SGI, CI gained more (P &lt; 0.05) weight than CON, and the AN that received a CI had increased weight gain when compared to the AN CON, SGI CON and SGI CI. There was no difference (P &gt; 0.05) in weight gain between the SGI that received a CI vs CON, nor was there a difference (P &gt; 0.05) between the CON SGI and AN. There was a treatment*breed interaction for BF (P &lt; 0.05), with AN tending to put on more BF than SGI CON (P &lt; 0.08). A breed*treatment interaction was also observed when analyzing BUN (P &lt; 0.05). This research provides preliminary evidence suggesting that anabolic implants are not as effective in Bos indicus influenced animals when compared to Bos taurus animals.

PSIX-28 Examining the effects of estradiol, trenbolone acetate, or polyamines on bovine satellite cell differentiation

The mechanism through which anabolic implants improve skeletal muscle growth of beef animals is incompletely understood. Polyamines (PA) are bioactive amino acid derivatives that act as potent growth stimulants. The objective of this study was to determine effects of anabolic implants, PA and their precursors on bovine satellite cell (BSC) differentiation. Primary BSC were cultured to approximately 80% confluency, at which time they were induced to differentiate in the presence of 3% horse serum (Con) and treated with 10nM TBA, 10 nM E2, or 10nM TBA and 10 nM E2 (ETBA), 10 mM methionine (Met), 8 mM ornithine (Orn), 2 mM putrescine (Put), 1.5 mM spermidine (Spd) or 0.5 mM spermine (Spe). Total mRNA was isolated 0, 2, 4, 8, 12, 24, or 48 h post-treatment and abundance of paired box transcription factor 7 (Pax7) and myogenic differentiation factor (MyoD) were analyzed. Treatment with the hormones (TBA, E2, or ETBA) and PA (Orn, Put, Spd, and Spe) increased (P &lt; 0.05) abundance of MyoD 4 h post-treatment when compared to Con cultures. However, 24 h post-treatment, MyoD abundance was decreased in the presence of hormone treatments when compared to the Con, while the PA treatments increased (P &lt; 0.05) abundance of MyoD when compared to the Con cultures. Treatment with either the hormones or PA had no effect (P &gt; 0.05) on Pax7 abundance at 2, 4, 8, 12, 24, or 48 h post-treatment when compared to Con cultures (P &gt; 0.05). These results indicate that treatment with PA or hormones increases abundance of MyoD, though temporally different indicating that these two classes of growth promoters impact differentiation via alternate physiological pathways. Additional research is underway in order to determine the effects of both PA and hormones on differentiation of primary BSC.