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Effects of source and level of zinc on feedlot performance and carcass characteristics in steers
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To determine the effects of source and level of dietary Zn on performance, carcass characteristics and tissue Zn concentration, Angus steers (n = 120; initial weight = 325 kg ︢2.57) were assigned to diets containing five levels of added Zn (5, 35, 95, 215, or 445 mg/kg) from Zn methionine (ZnMet) or ZnSO4 in a 2 x 5 factorial arrangement of treatments. Total dietary Zn was 30, 60, 120, 240 and 480 mg/kg. Within treatment groups, steers were assigned to one of two kill groups (kill group I = d 77; kill group 2 = d 126). Steers were housed four to a pen and fed ad libitum a 90% concentrate diet of primarily corn and cottonseed meal by electronic Calen gate feeders. At the time of slaughter, the right front metacarpal, a 150 g liver sample and the right kidney were obtained from each steer. Carcass cooler traits were determined 48 h post slaughter and soft tissue from 9-1 0-1 1 rib section was analyzed for water, protein and lipid content. Statistical models for carcass characteristics included carcass weight as a covariate. Steers fed ZnSO4 gained faster (P <.05) than steers fed ZnMet (2.01 vs 1.85 kg/d .︢048). However, feed intake and feed efficiency were similar for ZnSO4 and ZnMet supplemented steers (I 1.2 vs 10.9 kg/d and 178 vs 170 g gain/kg intake, respectively). There was no difference (P > . I 0) in ADG or feed efficiency due to level of Zn in the diet. Neither source nor level of Zn affected (P > . I 0) carcass characteristics. The composition of the 9-1 0-1 1 rib section was not affected (P > . I 0) due to dietary treatment. Zinc and Cu concentrations in the liver, kidney and bone were not affected (P > . 1 0) by source of Zn. Level of Zn, however, did affect tissue concentrations of Zn and Cu. Liver Zn was higher (P <.0007) in steers fed 480 mg/kg Zn compared to steers in any other treatment. Liver Cu decreased(P<.OOOI)as level of dietary Zn increased. Zinc and Cu content of the kidney was higher (P<.0001) in steers fed 480 mg/kg Zn than steers in any other treatment. Zinc concentration of the metacarpal was highest (P < .000 1) in steers fed 480 mg/kg Zn than steers receiving 30, 120 and 240 mg/kg Zn, but not different from steers fed 60 mg/kg Zn. Bone Cu was not affected (P > . I 0) by level of dietary Zn.
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Includes bibliographical references: p.54-59.
Issued also on microfiche from Lange Micrographics.
Nunnery, Greg Alan (1998). Effects of source and level of zinc on feedlot performance and carcass characteristics in steers. Master's thesis, Texas A&M University. Available electronically from
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