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.

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 > 0.10) on proliferation, protein synthesis, or mRNA abundance at any time point. Each treatment increased (p < 0.01) proliferation, and anabolic hormones increased (p = 0.04) protein synthesis. Polyamines increased (p < 0.05) the abundance of mRNA involved in polyamine biosynthesis, proliferation, and protein synthesis. Treatment with polyamine precursors decreased (p < 0.05) the abundance of mRNA involved in proliferation and protein synthesis. Overall, C2C12 and Sol8 myoblasts do not differ (p > 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.

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.

Cattle production in the U.S. is being impacted by the changing global climate and limited availability of natural resources. Improving the efficiency of cattle production is imperative to make the most of these limited resources. Increasing the percentage of Bos indicus (BI) genetics within cattle herds is one potential method to address these issues, as they are able to withstand higher temperatures, are better adapted to nutritional stress, and consume less water than Bos taurus (BT) influenced cattle. The objective of this study was to examine steers of different breed types relative to feedlot performance, feeding behavior, and carcass characteristics. This study utilized a total of 115 steers of two different breeds: Angus (AN; n=83; 100% BT) and Santa Gertrudis influenced (SG; n=32; 19% BI, 81% BT). Steers were stratified by weight and randomly divided into one of four covered pens. Each pen was equipped with two GrowSafe bunks and all steers were fed the same typical ration. All steers were harvested at a commercial facility once industry average backfat standards were met. Individual dry matter intake and feeding behaviors were collected through the GrowSafe system. Weight, ribeye fat thickness, marbling score, and USDA yield grades were also assessed. Breed did not have an effect (P &gt;0.10) on dry matter intake, average daily gain, ribeye fat thickness, hot carcass weight, or USDA yield grade. There was a tendency (P=0.09) for SG steers to spend more time with their heads down during individual GrowSafe bunk visits. Intramuscular fat was increased (P=0.0019) in AN steers compared to SG steers. Further research focused on genomic differences between cattle of different breed types is warranted to better understand the relationship between breed type and production performance characteristics.

Omega-3 fatty acids have immunomodulatory and anti-inflammatory effects. The objective of this project was to determine the effects of fish oil, a source of omega-3 fatty acids, on genes involved in inflammation and growth of skeletal muscle tissue after an LPS challenge. Male Landrace-New Hampshire weaned piglets (BW 8.21±0.83 kg) were used in a randomized complete block design and assigned to two treatments: 1) basal diet (n=7) and 2) basal diet plus 3% fish oil added (n = 7). Treatments were fed for 35 d. On d 34, an LPS challenge was performed and 24 h later, piglets were euthanized and skeletal muscle samples were collected from the longissimus lumborum and biceps femoris. Total mRNA was isolated and markers of inflammation [cyclophilin (Cyclo), nuclear factor kappa beta subunit-1 (NF-kB), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6)], skeletal muscle growth [paired box transcription factor-7 (Pax7), myogenic factor-5 (Myf5), myoblast determination factor-1 (MyoD), myogenin (MyoG)] and adipose growth (peroxisome proliferator activated receptor (PPARy), leptin, and adiponectin) were analyzed. Cyclophilin abundance was increased (P = 0.03) in fish-oil piglets compared to control piglets. Other markers of inflammation (TNF-α, IL-6, NF-kB) were not affected (P &gt; 0.05) by fish-oil supplementation. Abundance of Myf5 was lower (P = 0.03) in fish oil piglets than control piglets. Other myogenic regulatory factors (Pax7, MyoD, MyoG) were not (P &gt; 0.05) altered by treatment. Abundance of PPARy, leptin or adiponectin was not affected (P &gt; 0.05) by fish-oil supplementation. Muscle location influenced (P &lt; 0.01) abundance of leptin and adiponectin, with abundance being higher in the biceps femoris than in the longissimus lumborum. No other genes analyzed were impacted by muscle location (P &gt; 0.05). Our findings suggest that supplementation of omega-3 fatty acids via fish-oil may affect the inflammatory response and skeletal muscle growth. Further research is needed to evaluate the impact of these results on animal production.