# Hair hormone profiling as a non-invasive diagnostic approach for assessing long-term endocrine status and productivity in Hereford bulls

## TL;DR

This study shows that hormone levels in hair can predict beef cattle productivity and meat quality better than blood tests, offering a non-invasive diagnostic tool.

## Contribution

Hair hormone profiling is introduced as a non-invasive method to assess long-term endocrine status and productivity in beef cattle.

## Key findings

- Hair hormones like STH and insulin positively correlate with growth and carcass traits.
- Stress hormones like cortisol negatively affect live weight gain and meat quality.
- Reference intervals for 12 hormones in hair were established for diagnostic use.

## Abstract

Accurate evaluation of hormonal status is critical for optimizing growth performance and meat quality in beef cattle. Conventional matrices such as blood, saliva, and urine reflect only short-term fluctuations and are influenced by collection stress. Hair, as a retrospective biosubstrate, can integrate hormone secretion over time and serve as a non-invasive indicator of chronic endocrine activity. This study aimed to evaluate the relationship between hair hormone concentrations and productive performance in Hereford bulls and to establish reference intervals (RIs) for major hormones in hair.

A total of 200 Hereford bulls aged 15–18 months were reared under uniform feeding and housing conditions. Hair samples from the withers were processed into powder (d50 < 20 µm), and concentrations of 12 hormones, including cortisol, adrenaline, testosterone, estradiol, somatotropin (STH), thyroxine (T4), and insulin, were quantified by enzyme-linked immunosorbent assay. Slaughter data included live and carcass weights, yields, and physicochemical meat traits. Correlation analyses (Spearman) and stepwise multiple linear regression were used to determine hormonal predictors of productivity. RIs (2.5th–97.5th percentiles) were calculated according to American Society for Veterinary Clinical Pathology recommendations.

Hair and serum hormones correlated significantly only for STH (r = 0.69) and adrenocorticotropic hormone (r = 0.61). Cortisol and adrenaline were inversely related to anabolic hormones (testosterone and insulin) and showed negative associations with live weight gain, carcass weight, and meat yield, but positive associations with meat pH and lipid oxidation. STH, insulin, estradiol, testosterone, and T4 were positively related to growth rate, carcass composition, and protein content. Regression models identified STH as the strongest independent positive predictor (β = 0.49) and cortisol as the principal negative predictor (β = –0.35) of productivity. RIs for 12 hormones were established for diagnostic application.

Hair hormone analysis reliably reflects chronic endocrine status and predicts productive performance in beef cattle. Elevated stress hormones impair growth and meat quality, whereas anabolic hormones enhance carcass traits. The established RIs can serve as practical benchmarks for metabolic monitoring and herd management strategies in precision beef production.