Steers (n = 77) and heifers (n = 68) were assigned randomly to one of three treatment groups. Treatment groups were defined as: no implant, implanted twice with trenbolone acetate (Revalor S or H), or implanted twice with estrodial benzoate (Synovex S or H). Animals were fed to an estimated 10 mm backfat thickness and based on visual appraisal, were assigned a harvest date. Carcass characteristics, color space values, sarcomere length, fat and moisture determination, Warner-Bratzler shear force, and protein degradation were all measured. Implanted animals, as a whole, exhibited heavier hot carcass weights and larger ribeye areas than non-implanted animals. Animals implanted with Revalor displayed significantly lower marbling scores and lower yield grades than those from control or Synovex groups. The distribution of quality grades within treatment groups shifted, with implant groups displaying higher percentages of Select carcasses. Gender impacted percentage of extractable fat and marbling scores, with heifers displaying higher values than steers for both measurements. Both implant groups displayed higher (P < 0.05) Warner-Bratzler shear values following a 0- and 14-d aging periods. However, following the 21-d aging period, differences in tenderness were no longer present between non-implanted and implanted animals. Synovex treated animals displayed longer (P < 0.01) sarcomere lengths than control or Revalor. Differences (P < 0.001) in protein degradation were found between treatment groups. Across gender groups, the non-implanted cattle displayed the greatest amount of degradation (62%), followed by Synovex (48%,) and lastly Revalor (33%), all of which were different (P < .05) from each other. These results indicate that use of anabolic implants positively impacted lean muscle growth, yet was a detriment to quality. Also, tenderness was negatively impacted by the use of these compounds. However, this study found by aging product for at least 21 days, tenderness differences between implanted and non-implanted animals were significantly mitigated.

Master of Science / Department of Animal Sciences and Industry / James S. Drouillard / Exogenous growth promotants, such as the synthetic beta agonist zilpaterol hydrochloride (ZH), have been shown to increase carcass weight by repartitioning energy toward increased skeletal muscle at the expense of adipose tissue, which is associated with a decline in tenderness. More recently, essential oils such as menthol have been observed to have growth promoting properties in livestock. The objectives of this research were to determine effects of ZH on blood parameters and long chain fatty acids in plasma and adipose tissue, to determine if the decline in tenderness can be negated by temporary depletion of calcium during ZH supplementation, and to determine effects of crystalline menthol on blood parameters. Blood samples were collected in 7-d intervals during ZH administration. Zilpaterol hydrochloride decreased concentrations of plasma urea nitrogen and whole blood glucose (P < 0.10), but had no effects on concentrations of plasma glucose, lactate, beta-hydroxybutyrate, NEFA, or whole blood lactate (P > 0.10). Total long chain fatty acids of plasma and adipose tissue were unaffected (P > 0.10); however, ZH supplementation increased HCW, dressing percentage, and LM area (P < 0.10). Calcium was temporarily depleted during ZH supplementation in an attempt to increase tenderness of meat. No differences (P > 0.10) were observed for Warner-Bratzler shear force values, live animal performance, or carcass measurements. Addition of 0, 0.003, 0.03, 0.3% menthol (diet DM) to diets of steers resulted in a menthol × time within day interaction (P < 0.01) for IGF-1 concentration and BW; however, glucose, lactate, and PUN concentrations were unaffected (P > 0.05). Furthermore, concentrations of VFA were not different (P > 0.05), but production of fermentative gas was decreased (P < 0.01) when menthol was added at 0, 0.003, 0.03, 0.3% of substrate DM in a 24 h in vitro fermentation trial. Results from these studies suggest ZH improved efficiency of nutrient utilization for increased skeletal muscle growth; however, the decline in tenderness was not negated by the temporary depletion of calcium in the diet. Overall, ZH affected components related to increased skeletal muscle growth, but menthol did not affect blood parameters associated with growth.

Master of Science / Department of Animal Sciences and Industry / James S. Drouillard / Christopher D. Reinhardt / The effects of supplementing forms of flaxseed on plasma and longissimus muscle (LM) fatty acid (FA) composition, finishing performance, and carcass characteristics were evaluated in five studies. In study 1, steers were fed diets with soy oil (SO), ground flaxseed (Flaxseed), or urea formaldehyde condensation polymer treated flaxseed (UFCP). In study 2, steers were fed diets with SO, linseed oil (LO), or a combination of flaxseed and field peas that was extruded (LinPro). Feeding flaxseed products increased (P < 0.01) α-linolenic acid (ALA), omega-3 FA, and decreased (P < 0.01) n-6:n-3 in LM compared to cattle fed SO. Feeding LinPro increased (P < 0.01) ALA, omega-3 FA, and decreased (P < 0.01) n-6:n-3 in LM compared to steers fed SO or LO. In studies 3 and 4, steers were fed diets with and without Flaxseed and implanted or not. Implanting improved (P ≤ 0.05) DMI, ADG, feed efficiency, HCW, and LM area compared to cattle not implanted. In study 4, cattle fed Flaxseed had increased (P < 0.01) ALA and omega-3 FA, and decreased (P < 0.01) n-6:n-3 in LM compared to cattle fed SO. In study 5, heifers were fed diets with 0% or 5% linseed meal, and administered with or without exogenous hormones (NHTC). Administering exogenous hormones improved (P ≤ 0.02) DMI, ADG, G:F, and HCW compared to NHTC cattle. Omega-3 FA increased in LM when cattle were supplemented with flaxseed products. Cattle fed LinPro achieved the highest levels of ALA and omega-3 FA. Flaxseed products did not interact with implants as a natural growth promoter in finishing cattle.