# Effects of Zilpaterol Hydrochloride Supplementation on Growth Performance, Carcass Characteristics and Meat Quality for Steers Differing in Breed Type

## TL;DR

This study examines how zilpaterol hydrochloride affects growth, carcass traits, and meat quality in different types of beef cattle.

## Contribution

The study provides new insights into the effects of ZH on British and British × Continental steers, focusing on breed-specific responses.

## Key findings

- ZH improved loin muscle area and yield grade in steers.
- ZH increased Warner–Bratzler shear force, indicating tougher meat.
- ZH had minimal impact on composition of gain and meat quality in both breed types.

## Abstract

The β–adrenergic agonist zilpaterol hydrochloride (ZH) enhances skeletal muscle growth in beef cattle, resulting in a shift in the composition of gain. This results in improvements in feedlot performance and carcass yield but has been reported to decrease marbling score and beef tenderness. British (B) and British × Continental (BC) cattle possess inherent differences in muscle and fat composition and may respond differently to the growth-promoting mechanism of ZH. Therefore, the objective of this study was to determine the effects of ZH on growth performance, carcass characteristics and meat quality for B and BC steers. Steers with B (n = 76) or BC (n = 57) backgrounds were assigned to a control (no ZH) or ZH-supplemented treatment group. Cumulative growth performance was evaluated. Steers were subjected to ultrasound immediately before ZH supplementation and following withdrawal of ZH to evaluate changes in body composition. After harvest, carcass data were recorded, and muscle samples were collected to determine impacts on meat quality. Inclusion of ZH largely did not impact composition of gain and meat quality characteristics of B and BC cattle. Supplementation with ZH did improve loin muscle area and yield grade for steers but increased Warner–Bratzler shear force, indicating tougher steaks.

To determine the effects of zilpaterol hydrochloride (ZH) on growth performance, carcass characteristics and meat quality for steers differing in breed type, steers with British (B; n = 76) or British × Continental (BC; n = 57) backgrounds were allocated to a randomized incomplete block design with a 2 × 2 treatment structure. Pens within each block × breed type were randomly assigned to either ZH (8.3 mg/kg of DM; fed for 20 d before slaughter, followed by a 3-day withdrawal) or control (CON; 0 mg/kg ZH). Steers were subjected to ultrasound immediately before ZH inclusion and following withdrawal to determine the influence of ZH on changes in longissimus muscle area (LMA), fat thickness and percent intramuscular fat (IMF). Carcass data were collected, and the longissimus lumborum was collected for analysis of tenderness, moisture percentage, crude fat content, collagen content, postmortem proteolysis and sensory attributes. The ZH × breed type interaction did not influence (p > 0.05) the feedlot performance, carcass or meat quality attribute traits evaluated, with the exception of moisture percentage. Responses among breed types were as expected for B vs. BC cattle types. Supplementation with ZH improved (p < 0.05) LMA and yield grade but increased Warner–Bratzler shear force.