The Effects of Different Zilpaterol Hydrochloride Feed Supplements and Extended Aging Periods on the Meat Quality of Feedlot Bulls

This study researched the effects of two commercially available zilpaterol hydrochloride (ZH) β-adrenergic agonists, denoted as ZH-A and ZH-B, on the meat quality characteristics of typical South African feedlot bulls (taurine × indicus composites), over extended aging periods of up to 120 days. The effects of ZH were studied to address concerns about the possible adverse effects of ZH on beef quality following extended aging, which typically occurs during the exportation of beef by boat. The completely randomized control study consisted of 3 homogenous experimental groups, with 3 replicates per treatment and 50 bulls per replicate = 450 animals. Treatments were a negative control (CT) with no ZH supplementation added to the basal diet or a basal diet supplemented with either zilpaterol hydrochloride A (ZH-A) or zilpaterol hydrochloride B (ZH-B), both at 105 g ZH/ton, fed from the first day of the finishing period (D0) for 30 days. Subsamples were collected from 38 random carcasses from each treatment for proximate analysis and meat quality analysis using Longissimus dorsi samples. ZH supplementation decreased meat tenderness (Warner-Bratzler shear force values (WBSF)) of bulls fed ZH-A or ZH-B, compared to those fed the CT diet (p < 0.05; η2 = 0.24). The WBSF values of both ZH treatments were about 0.5-0.8 kg higher during the aging periods compared to the CT, but ZH did not affect post-mortem meat aging or meat quality characteristics differently compared to the CT. Post-mortem aging per se influenced all meat quality characteristics investigated (p < 0.001; η2 > 0.30), showing improvements in WBSF, a decrease in meat colour and an increase in drip and cooking losses. L*-values increased from 3 to 56 days of aging and then decreased to day 120 (p < 0.001; η2 = 032). Chroma values decreased from day 3 to day 120 (p < 0.001; η2 = 0.50). Hue° decreased from day 3 to day 7 and stabilized until day 120 (p < 0.001; η2 = 0.40). Moisture and cooking loss (CL) increased to 56 days and then decreased to 120 days.

Variations in Low Electrical Stimulator Voltage Settings Minimally Influence Beef Longissimus Muscle Slice Shear Force Values

The objective of the current study was to evaluate the effect of differing electrical stimulation (ES) voltage levels on beef longissimus muscle tenderness, postmortem temperature, pH decline, and carcass quality. Beef carcasses from 3 commercial beef processing plants (A, B, C) were exposed to 3 varying voltage levels: (1) control (no ES), (2) ES level 1 (ES1; 60 Hz for 17 s each at 16, 20, 24, and 28 V), and (3) ES level 2 (ES2; 60 Hz for 17 s each at 25, 35, 45, and 55 V) prior to chilling. Ninety beef carcasses were selected from each of the 3 plants, and within a carcass, paired sides were randomly assigned to one of 3 ES treatments (n = 60 sides/treatment/plant). The results indicated that ES affected (P &lt; 0.05) muscle pH at 3 h postmortem in 2 of the 3 plants. However, ES did not affect (P &gt; 0.05) pH at the time of grading (postrigor). Although the slice shear force (SSF) values were lower (P &lt; 0.05) for ES steaks compared with controls, voltage did not affect (P &gt; 0.05) SSF values. Variation in SSF was observed among the plants (P &lt; 0.05), with steaks from Plant C having greater (P &lt; 0.05) SSF values compared with steaks from Plants A and B, which exhibited similar (P &gt; 0.05) SSF values. Overall, although ES steaks had lower SSF values compared with control steaks, the lack of difference in postmortem tenderness between ES1 and ES2 voltage settings indicated that the low ES voltages minimally influenced SSF values.