title: Effect of anabolic implants on adrenal cortisol synthesis in feedlot beef cattle implanted early or late in the finishing phase.
abstract: Implantation of anabolic steroids to increase growth rate in beef cattle impacts adrenal glucocorticoid production. The mechanism by which combination androgen and estrogen implants reduce cortisol biosynthesis in heifers is not clear. The objective of this study was to identify whether pituitary or adrenal gene expression and liver enzyme activity may contribute to altered serum cortisol concentrations in heifers receiving a combination implant. On d 0 of a 122-d finishing phase, 187 predominantly Angus heifers (361 kg) approximately 14 months old were randomly assigned to one of three implant groups: (1) non-implanted control, (2) implanted at the beginning of the finishing phase (d 0; early implant) with a combination implant (200mg TBA+20mg E2; Revalor 200®), and (3) implanted during the late stage of the finishing phase (d 56; late implant) with Revalor 200®. At d 56, body weight (BW) was greater (P<0.0001) for the early implanted heifers (456 ± 1.9 kg) compared to 437 and 435 (± 1.8) kg for control and late implanted heifers, respectively. Final BW (d 122) was similar between both implanted groups and heavier than non-implanted controls (P<0.0001). Serum cortisol was similar among groups at d 0 (P=0.86) however, by d 28 heifers receiving the combination implant had reduced (P<0.05) serum cortisol concentrations (31.2 ng/mL) compared to controls (49.4 ng/mL) and late (48.2 ng/mL) groups. On d 84 cortisol was similar (P=0.75) among implanted heifers and was less (P<0.01) than non-implanted heifers. Expression of pituitary and adrenal genes involved in glucocorticoid synthesis was evaluated at d 28/29 or 84/85; however, despite decreased serum cortisol in implanted heifers, no change in mRNA expression was demonstrated. Liver CYP3A enzyme activity at d 28/29 was decreased 59% in early implanted heifers compared to control heifers (P=0.01). Additionally, at d 84/85 AKR1C activity was greatest (P=0.01) in control heifers compared to both implanted groups. Data suggest that components of hypothalamic-pituitary-adrenal axis are influenced by exposure to exogenous hormones and this should be recognized when considering cortisol levels as a marker for stress response.
authors.affiliation: Oklahoma State University, Department of Animal Science, Stillwater, OK 74078, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Gifford
authors.affiliation: Oklahoma State University, Department of Animal Science, Stillwater, OK 74078, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Branham
authors.affiliation: Oklahoma State University, Department of Animal Science, Stillwater, OK 74078, USA.
authors.forename: J O
authors.initials: JO
authors.lastname: Ellison
authors.affiliation: Oklahoma State University, Department of Animal Science, Stillwater, OK 74078, USA.
authors.forename: B I
authors.initials: BI
authors.lastname: Gómez
authors.affiliation: Mississippi State University, Department of Animal and Dairy Sciences, Mississippi State, MS 39762, USA.
authors.forename: C O
authors.initials: CO
authors.lastname: Lemley
authors.affiliation: Mississippi State University, Department of Animal and Dairy Sciences, Mississippi State, MS 39762, USA.
authors.forename: C G
authors.initials: CG
authors.lastname: Hart
authors.affiliation: Oklahoma State University, Department of Animal Science, Stillwater, OK 74078, USA.
authors.forename: C R
authors.initials: CR
authors.lastname: Krehbiel
authors.affiliation: Oklahoma State University, Department of Animal Science, Stillwater, OK 74078, USA.
authors.forename: B C
authors.initials: BC
authors.lastname: Bernhard
authors.affiliation: Oklahoma State University, Department of Animal Science, Stillwater, OK 74078, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Maxwell
authors.affiliation: Oklahoma State University, Department of Statistics, Stillwater, OK 74078, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Goad
authors.affiliation: New Mexico State University, Department of Animal and Range Sciences, Las Cruces, NM 88003, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Hallford
authors.affiliation: Oklahoma State University, Department of Animal Science, Stillwater, OK 74078, USA. Electronic address: jah.hernandez_gifford@okstate.edu.
authors.forename: J A
authors.initials: JA
authors.lastname: Hernandez Gifford
mesh_terms: D015089:20-Hydroxysteroid Dehydrogenases / Q000378:metabolism; D000311:Adrenal Glands / Q000187:drug effects* / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D045930:Anabolic Agents / Q000494:pharmacology*; D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000378:metabolism*; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D004343:Drug Implants; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006854:Hydrocortisone / Q000097:blood*; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D010902:Pituitary Gland / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000097:blood; D011863:Radioimmunoassay; D011897:Random Allocation; D060888:Real-Time Polymerase Chain Reaction; D013252:Steroid 11-beta-Hydroxylase / Q000378:metabolism; D013315:Stress, Psychological / Q000188:drug therapy* / Q000378:metabolism; D013997:Time Factors
chemical_list: D045930:Anabolic Agents; D004343:Drug Implants; D012333:RNA, Messenger; D000324:Adrenocorticotropic Hormone; D015089:20-Hydroxysteroid Dehydrogenases; D051544:Cytochrome P-450 CYP3A; D013252:Steroid 11-beta-Hydroxylase; D006854:Hydrocortisone
keywords: Anabolic implant; Bovine; Cortisol; Heifer; Stress