Skeletal Muscle Growth of Beef Cattle: Cattle Breed Types and Anabolic Implants

Two potential methods that can be used by the U.S. to help further improve environmental and economic sustainability of the beef industry are through the use anabolic implants, typically composed of the hormones estradiol and trenbolone acetate, and by crossbreeding Bos taurus and Bos indicus cattle. How anabolic implants operate to improve growth, and their resulting relationship with different cattle breed types have yet to be determined. However, crossbreeding these cattle breed types has been found to have a positive influence on economically important traits such as average daily gain and carcass characteristics. Therefore, we hypothesized that the different hormones utilized in anabolic implants will operate through different mechanisms from each other, while causing changes in a breed dependent manner due to the innate physiological difference between different cattle breed types. This research found that estradiol primarily improved growth by altering nutrient partitioning in skeletal muscle of feedlot steers, while trenbolone acetate increased mRNA abundance associated with skeletal muscle growth. Furthermore, this research found that anabolic implants elicit changes in feeding behavior, animal temperament, serum metabolites, feedlot performance, carcass characteristics, and mRNA associated with protein turnover in a breed dependent manner. Economic return always improved when feedlot steers were implanted, however the extent of this return varied based off breed and implant protocol used. Therefore, the findings from this research suggest that anabolic implant protocols need to be optimized to match cattle breed types to help further improve environmental and economic sustainability of beef production in the U.S

The Benefits of Growth-Promoting Implants for Beef Cattle

Growth-promoting implants have been used in the cattle industry for decades. Their benefits allow cattle producers to become more sustainable by decreasing the amount of resources used. Resources such as water and land are decreased when using growth-promoting implants in beef cattle

Understanding the Influence of Trenbolone Acetate and Polyamines on Proliferation of Bovine Satellite Cells

Approximately 90% of beef cattle on feed in the United States receive at least one anabolic implant, which results in increased growth, efficiency, and economic return to producers. However, the complete molecular mechanism through which anabolic implants function to improve skeletal muscle growth remains unknown. This study had 2 objectives: (1) determine the effect of polyamines and their precursors on proliferation rate in bovine satellite cells (BSC); and (2) understand whether trenbolone acetate (TBA), a testosterone analog, has an impact on the polyamine biosynthetic pathway. To address these, BSC were isolated from 3 finished steers and cultured. Once cultures reached 75% confluency, they were treated in 1% fetal bovine serum (FBS) and/or 10 nM TBA, 10 mM methionine (Met), 8 mM ornithine (Orn), 2 mM putrescine (Put), 1.5 mM spermidine (Spd), or 0.5 mM spermine (Spe). Initially, a range of physiologically relevant concentrations of Met, Orn, Put, Spd, and Spe were tested to determine experimental doses to implement the aforementioned experiments. One, 12, or 24 h after treatment, mRNA was isolated from cultures and abundance of paired box transcription factor 7 (Pax7), Sprouty 1 (Spry), mitogen-activated protein kinase-1 (Mapk), ornithine decarboxylase (Odc), and S adenosylmethionine (Amd1) were determined, and normalized to 18S. No treatment × time interactions were observed (P ≥ 0.05). Treatment with TBA, Met, Orn, Put, Spd, or Spe increased (P ≤ 0.05) BSC proliferation when compared with control cultures. Treatment of cultures with Orn or Met increased (P ≤ 0.01) expression of Odc 1 h after treatment when compared with control cultures. Abundance of Amd1 was increased (P \u3c 0.01) 1 h after treatment in cultures treated with Spd or Spe when compared with 1% FBS controls. Cultures treated with TBA had increased (P \u3c 0.01) abundance of Spry mRNA 12 h after treatment, as well as increased mRNA abundance of Mapk (P \u3c 0.01) 12 h and 24 h after treatment when compared with 1% FBS control cultures. Treatment with Met increased (P \u3c 0.01) mRNA abundance of Pax7 1 h after treatment as compared with 1% FBS controls. These results indicate that treatments of BSC cultures with polyamines and their precursors increase BSC proliferation rate, as well as abundance of mRNA involved in cell proliferation. In addition, treatment of BSC cultures with TBA, polyamines, or polyamine precursors impacts expression of genes related to the polyamine biosynthetic pathway and proliferation

Understanding the Effects of Trenbolone Acetate, Polyamine Precursors, and Polyamines on Proliferation, Protein Synthesis Rates, and the Abundance of Genes Involved in Myoblast Growth, Polyamine Biosynthesis, and Protein Synthesis in Murine Myoblasts

Research suggests that androgens increase skeletal muscle growth by modulating polyamine biosynthesis. As such, the objective of this study was to investigate effects of anabolic hormones, polyamine precursors, and polyamines relative to proliferation, protein synthesis, and the abundance of mRNA involved in polyamine biosynthesis, proliferation, and protein synthesis in C2C12 and Sol8 cells. Cultures were treated with anabolic hormones (trenbolone acetate and/or estradiol), polyamine precursors (methionine or ornithine), or polyamines (putrescine, spermidine, or spermine). Messenger RNA was isolated 0.5 or 1, 12, or 24 h post-treatment. The cell type had no effect (p \u3e 0.10) on proliferation, protein synthesis, or mRNA abundance at any time point. Each treatment increased (p \u3c 0.01) proliferation, and anabolic hormones increased (p = 0.04) protein synthesis. Polyamines increased (p \u3c 0.05) the abundance of mRNA involved in polyamine biosynthesis, proliferation, and protein synthesis. Treatment with polyamine precursors decreased (p \u3c 0.05) the abundance of mRNA involved in proliferation and protein synthesis. Overall, C2C12 and Sol8 myoblasts do not differ (p \u3e 0.10) in proliferation, protein synthesis, or mRNA abundance at the time points assessed. Furthermore, anabolic hormones, polyamines, and polyamine precursors increase proliferation and protein synthesis, and polyamines and their precursors alter the abundance of mRNA involved in growth

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

Myokines Produced by Cultured Bovine Satellite Cells Harvested from 3- and 11-Month-Old Angus Steers

The myokines interleukin 6 (IL-6), interleukin 15 (IL-15), myonectin (CTRP15), fibronectin type III domain containing protein 5/irisin (FNDC5), and brain-derived neurotrophic factor (BDNF) are associated with skeletal muscle cell proliferation, differentiation, and muscle hypertrophy in biomedical model species. This study evaluated whether these myokines are produced by cultured bovine satellite cells (BSCs) harvested from 3- and 11-month-old commercial black Angus steers and if the expression and secretion of these targets change across 0, 12, 24, and 48 h in vitro. IL-6, IL-15, FNDC5, and BDNF expression were greater (p ≤ 0.05) in the differentiated vs. undifferentiated BSCs at 0, 12, 24, and 48 h. CTRP15 expression was greater (p ≤ 0.03) in the undifferentiated vs. differentiated BSCs at 24 and 48 h. IL-6 and CTRP15 protein from culture media were greater (p ≤ 0.04) in undifferentiated vs. differentiated BSCs at 0, 12, 24, and 48 h. BDNF protein was greater in the media of differentiated vs. undifferentiated BSCs at 0, 12, 24, and 48 h. IL-6, 1L-15, FNDC5, and BDNF are expressed in association with BSC differentiation, and CTRP15 appears to be expressed in association with BSC proliferation. This study also confirms IL-6, IL-15, CTRP15, and BDNF proteins present in media collected from primary cultures of BSCs