Effects of duration of zilpaterol hydrochloride supplementation on growth performance, carcass traits and meat quality of grain-fed cull cows

Abstract

Several studies have shown that feeding of an energy-dense diet over short periods to cull cows could be profitable in terms of increased saleable yield and improved carcass conditions. Although the application of growth promoters, such as anabolic implants and beta agonists, in finishing of cull cows have been recorded, there is no conclusive evidence as to the timing and duration of beta agonists in cull cow production. In this study, 288 cull cows with four or more permanent incisors and varying weights and body conditions were divided into four treatment groups so that variation in age, weight and body condition were equally distributed among groups. One group received concentrate feed without any beta agonist (C), whereas the other three groups also received concentrate feed with zilpaterol hydrochloride (6 p.p.m.) for 20 (Z20), 30 (Z30) or 40 (Z40) days, respectively, followed by a 2-day withdrawal. Animals were adapted for 10 days on a grain-based diet and fed an additional 40 days before slaughter. Growth rate and efficiency (live and carcass), trimmed meat yield and meat tenderness (Warner Bratzler shear force and sensory) of the aged (10 days) m. longissimus thoracis (LT) and m. semitendinosus (ST) were recorded. In general, Z cows had higher carcass gains and efficiency of gain than C cows ( P , 0.05). In addition, Z carcasses showed higher proportional trimmed meat yields than C carcasses ( P , 0.05). No significant differences in tenderness measurements were recorded for LT or ST. In general, supplementation of zilpaterol for 30 days showed better growth performance and higher trimmed meat yield than 20 and 40 days supplementation.

Effects of zilpaterol hydrochloride on growth performance, carcass characteristics, and wholesale cut yield of hair-breed ewe lambs consuming feedlot diets under moderate environmental conditions

“…These results agree with effects of ZH on fat deposition of finishing ewe lambs under heat stress (Macias-Cruz et al, 2010). In general, several studies in the literature in which effects of ZH were evaluated on deposition of internal fat in heifers and culled cows agree with the results of the present study Neill et al, 2009;Robles-Estrada et al, 2009a;Strydom and Smith, 2010). Zilpaterol is considered a repartitioning agent that primarily functions through an increase of protein deposition, whereas other composition factors such as moisture, fat, and ash seem to be minimally affected (Leheskaet al, 2009).…”

Effects of feeding a single or sequence of beta-adrenergic agonists on cull cow meat quality

“…After 10 d and 21 d of aging, LM steaks from ZH and RH+ZH treatments had a lower (Pb 0.0001) percentage of degraded desmin than steaks from C cows or cows supplemented only with RH. As expected, for all treatments, a higher percentage of degraded desmin was present after 21 d of postmortem aging than at 10 d. In contrast to our results, Kellermeier et al (2009) reported that ZH supplementation in steers did not alter desmin degradation in LM steaks aged for 7, 14, and 21 d. In support of our results, Strydom and Smith (2010) reported increased calpastatin activity in steaks from β-AA-supplemented steers. We speculate that desmin degradation was lower in ZH-fed cattle because of increased muscle calpastatin activity, and, thereby, reduced postmortem proteolysis.…”

“…In young cattle, β-AA have profound effects on growth performance and carcass yields, but several studies have shown that the effectiveness of β-AA in mature cows is less pronounced (Carter, Johnson, Thrift, & Foster, 2006;Harborth, 2006;Holmer, Homm, Berger, McKeith, & Killefer, 2009;Neill et al, 2009). In contrast, Strydom and Smith (2010) and Lawrence, Gasch, Hutcheson, and Hodgen (2011) reported increased performance, carcass yield, and conformation scores when cows were supplemented with ZH at 8.33 mg head −1 for 30 d.…”

Feeding zilpaterol hydrochloride is associated with decreased dry matter intake shortly after initiation of feeding dependent on season and previous intake1

“…There is divergence in the reported effects of zilpaterol on DMI, with reports ranging from small to moderate decreases in DMI (Baxa et al, 2010;Holland et al, 2010;Parr et al, 2011) to reports of greater decreases (Scramlin et al, 2010;McKevers et al, 2012a). South African researchers have reported reduced DMI of 6% in steers (Strydom et al, 2008) and 5% in cull cows (Strydom and Smith, 2010) fed ZIL at 6 mg/kg, although these reductions were not statistically significant. Vasconcelos 2008) demonstrated a 0.40 kg reduction in DMI when ZIL was fed for 40 d at 72 mg/animal daily but no effect on DMI for cattle fed ZIL at 75 mg/animal daily for 20 d. Montgomery et al (2009a) reported a ZIL × sex interaction for DMI; steers did not have a reduction in DMI during ZIL administration but heifers had a 0.52 kg reduction in DMI during the ZIL-feeding period.…”