Abstract
Interactive effects of supplemental Zn and ractopamine hydrochloride (RH) were evaluated using 156 crossbred heifers (initial BW = 527 kg ± 6.61; gross BW × 0.96) to determine impact on feedlot performance, plasma urea nitrogen (PUN) and carcass characteristics. The study was conducted as a randomized complete block design with a 2 × 2 factorial arrangement. Factors consisted of: 1) 30 or 100 mg supplemental Zn/kg diet DM (30Zn or 100Zn) as Zn sulfate, and 2) 0 or 200 mg RH/animal daily. Heifers were blocked by BW and, assigned randomly within block to treatments. Heifers were housed in partially covered feeding pens (3 heifers/pen; 13 pens/treatment), fed once daily ad libitum, and RH was fed for 42 d and removed from the diet until cattle were harvested on d 43. Plasma samples were collected on d 0 and 36 to assess changes in plasma Zn and PUN. On d 43, heifers were transported to a commercial abattoir where HCW and incidence of liver abscesses were recorded. Carcass data were collected after 32 h of refrigeration. No Zn × RH interactions were observed for plasma Zn or PUN (P ≥ 0.58); however, there was a tendency for RH × d interaction for PUN (P = 0.08). Supplementing 100Zn increased plasma Zn concentration (P = 0.02) compared to 30Zn. No interactions were observed for feedlot performance (P ≥ 0.24). Final BW and ADG increased with RH supplementation (P ≤ 0.02), but DMI was not affected (P = 0.63), thus feed efficiency improved (P < 0.01) when cattle were fed RH. Supplementing 100Zn tended to reduce ADG (P = 0.07), but did not affect other measures of feedlot performance or incidence of liver abscesses (P ≥ 0.12). Zinc × RH interactions were observed for LM area and yield grade (P ≤ 0.01); LM area decreased and yield grade increased when cattle were supplemented 100Zn with no RH compared to other treatments. A tendency for Zn × RH interaction was detected for dressing percentage (P = 0.08), but no other interactions or effects of Zn were observed for carcass traits (P ≥ 0.11). Supplementing RH increased HCW (P = 0.03), but did not affect other carcass traits (P ≥ 0.13). In conclusion, supplemental Zn had little impact on feedlot performance or PUN concentration, but may alter muscle and fat deposition when fed in conjunction with RH.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.