Feedlot performance, carcass characteristics, hormones, and metabolites in steers actively immunized against growth hormone-releasing factor.
Harvey. R W RW; Armstrong. J D JD; Heimer. E P EP; Campbell. R M RM
Key Findings
- Vaccinating steers against GRF‑1‑29 reduced their weight gain by about 34–48 kg over the study period.
- Carcass weight was about 28 kg lower in the GRF‑immunized group.
- Feed intake stayed the same, but feed efficiency dropped, meaning the animals got less growth per unit of feed.
- Marbling scores (intramuscular fat) were lower in GRF‑immunized steers, though most still met a low‑choice grade.
Practical Outcomes
- For human biohackers, the study shows that blocking GRF can blunt growth and reduce muscle‑lean gains in a large animal model, but it offers no direct protocol for supplementation. It suggests that the peptide’s activity matters for growth, yet the immunization approach isn’t applicable to people, so the relevance to everyday longevity or performance strategies is minimal.
Summary
In this cattle study, scientists vaccinated steers against the hormone‑releasing peptide GRF‑1‑29. The vaccinated animals grew less, weighed less at slaughter, and were less efficient at turning feed into body mass, while their meat quality (marbling) was also slightly lower. Food intake didn’t change, so the effect was due to the hormone block, not less eating.
Abstract
Large-framed Simmental and Charolais steers were actively immunized against growth hormone-releasing factor (GRF) to evaluate the effect on growth, carcass characteristics (especially intramuscular fat deposition), and concentrations of somatotropin (ST) and IGF-I. Primary immunizations of 1.5 mg of GRF-(1-29)-Gly-Gly-Cys-NH2 conjugated to 1.5 mg of human serum albumin (GRFi, n = 12) or 1.5 mg of human serum albumin (HSAi, n = 12) were given at approximately 10 mo of age. Booster immunizations of .5 mg of the appropriate antigen were given at d 49 and 125. Weights of steers administered GRFi were less (P < .05) than those given HSAi at 126 d (34.6 kg) or at 262 d (48.2 kg) after treatment. Carcass weights were 28.2 kg less (P < .01) for GRFi than for HSAi steers. Dry matter intake was not affected by immunization treatment, whereas feed efficiency was reduced in GRFi steers. Marbling scores were higher (P < .05) for HSAi than for GRFi steers but similar percentages (83.3) of both treatments graded Low Choice or higher. Rib sections of GRFi steers contained more fat (31.2 vs 25.0%) and less lean (63.3 vs 68.4%) than those of HSAi steers (P < .05). A breed x treatment interaction was observed for percentage of fat within the trimmed longissimus muscle (P < .05); percentage of fat was similar for Charolais and Simmental steers when immunized against HSAi but was higher for Simmental than for Charolais when immunized against GRFi.(ABSTRACT TRUNCATED AT 250 WORDS)
Study Information
pubmed
1993
10.2527/1993.71112853x