Effects of growth hormone-releasing factor and(or) thyrotropin-releasing hormone on growth, feed efficiency, carcass characteristics, and blood hormones and metabolites in beef heifers.
Enright. W J WJ; Prendiville. D J DJ; Spicer. L J LJ; Stricker. P R PR; Moloney. A P AP; Mowles. T F TF; Campbell. R M RM
Key Findings
- GRF‑1‑29 alone raised GH on day 36 and IGF‑1 on day 1; GRF‑1‑29 + TRH raised GH on days 1, 36, and 78.
- The combination (GRF + TRH) lowered feed intake and increased longissimus muscle area, while reducing fat score.
- No changes were seen in overall weight gain, carcass weight, or most blood metabolites; effects were modest and species‑specific.
Practical Outcomes
- For human biohackers, the data suggest GRF‑1‑29 can stimulate GH and may improve muscle‑to‑fat ratio, but the benefits were small and observed in cattle, not people. Translating the dose and effects to humans would require careful testing, so this study offers limited direct guidance for self‑experimentation.
Summary
In a study on beef heifers, giving a growth‑hormone‑releasing factor (GRF‑1‑29) alone or together with thyrotropin‑releasing hormone (TRH) modestly raised growth‑hormone levels, slightly improved feed efficiency, and increased muscle size while reducing fat, but it didn’t make the animals grow faster overall.
Abstract
The objective of this study was to determine the effect of long-term administration of a growth hormone (GH)-releasing factor analog (GRFa) and(or) thyrotropin-releasing hormone (TRH) on growth, feed efficiency, carcass characteristics, and blood hormones and metabolites in beef heifers. Crossbred heifers (n = 48; 345.9 +/- 2.8 kg) were divided into four equal groups: control (vehicle), 1 microgram of GRFa (human GRF 1-29 analog).kg BW-1.d-1, 1 microgram of TRH.kg BW-1.d-1, or GRFa + TRH. Daily s.c. injections continued for 86 d. Blood samples were collected from half of the heifers after injection on d 1, 36, and 78. On d 89, all heifers were slaughtered. Treatments did not affect (P > .05) ADG but GRFa + TRH decreased (P < .05) ADFI relative to all other treatments. Feed conversion efficiency tended (P < .10) to be improved in the groups given GRFa alone or TRH alone. Treatment with GRFa and(or) TRH did not affect carcass weight, dressing percentage, conformation score, backfat thickness, or weights of liver, kidneys, pituitary, and ovaries. The GRFa + TRH treatment reduced (P < .05) fat score and increased (P < .05) longissimus muscle area relative to other treatments. The GRFa treatments reduced (P < .05) the weight and fat percentage of the mammary gland and increased (P < .05) heart weight. Treatment with TRH alone failed to stimulate GH on d 1, 36, and 78. Treatment with GRFa alone increased (P < .05) GH above controls on d 36, whereas GRFa + TRH increased (P < .05) GH on d 1, 36, and 78. Treatment with GRFa alone increased (P < .05) IGF-I only on d 1, whereas GRFa + TRH was without effect on all days. Across sampling days, treatments had little effect on blood concentrations of insulin, triiodothyronine, nonesterified fatty acids, urea nitrogen, and glucose. The GRFa alone and GRFa + TRH decreased (P < .05) and TRH alone increased (P < .05) thyroxine concentrations. In conclusion, with the dose and administration regimen used, GRFa and(or) TRH yielded small but positive improvements in animal performance.
Study Information
pubmed
1993
10.2527/1993.7192395x