title: Effects of increasing dosages of zeranol implants on lamb growth, carcass characteristics, blood hormones, and nitrogen metabolism.
abstract: The objective of this research was to compare the growth performance, incidence of prolapse and mortality, carcass characteristics, blood hormone concentration, and N balance of lambs implanted with increasing dosages of zeranol. One hundred forty-four crossbred lambs (29.6 ± 4.9 kg) were used in a completely random design and placed into 16 feedlot pens (4 pens/treatment) for a 116 d finishing study. Lambs were fed an 84.7% corn and 15.3% market lamb pellet (DM basis) diet ad libitum. Treatments were 0, 12, 24, and 36 mg zeranol (Ralgro; Schering-Plough), and lambs were implanted in the ear according to treatment on d 0. Lambs were weighed. Thirty lambs (67.6 ± 3.4 kg) and 96 lambs (65.8 ± 5.1 kg) were harvested on d 84 and d 118, respectively. Carcass data were collected 24 h after chill. Blood samples were collected on d 0, 28, 56, 70, 82, 99, and 116 from 64 lambs (29.6 ± 2.1 kg) in the feedlot study (subsample of 4 lambs per pen) and analyzed for thyroxine, triiodothyronine, and IGF-I. A second study was conducted to compare effects of 0, 12, 24, or 36 mg zeranol on N balance in 16 crossbred lambs (34.8 ± 2.1 kg). There were no differences among treatments for BW, ADG, DMI, and G:F (P > 0.05) in the feedlot study. However, there was a linear increase for incidence of prolapse (P = 0.006; 2.78, 5.55, 24.98, and 27.75%, respectively) and mortality (P = 0.005; 0.00, 5.55, 11.10, and 13.88%, respectively) as zeranol dosage increased. Carcass characteristics, blood hormone concentrations, and N balance were not affected by treatment (P > 0.05). These results indicate zeranol increases incidence of prolapse and mortality without increasing growth performance.
authors.affiliation: North Dakota State University, Hettinger Research Extension Center, Hettinger 58639, USA.
authors.forename: S R
authors.initials: SR
authors.lastname: Eckerman
authors.forename: G P
authors.initials: GP
authors.lastname: Lardy
authors.forename: M M
authors.initials: MM
authors.lastname: Thompson
authors.forename: M L
authors.initials: ML
authors.lastname: Van Emon
authors.forename: B W
authors.initials: BW
authors.lastname: Neville
authors.forename: P T
authors.initials: PT
authors.lastname: Berg
authors.forename: C S
authors.initials: CS
authors.lastname: Schauer
mesh_terms: D000818:Animals; D001823:Body Composition / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004968:Estrogens, Non-Steroidal / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D009584:Nitrogen / Q000378:metabolism*; D012756:Sheep / Q000097:blood / Q000254:growth & development* / Q000502:physiology*; D013963:Thyroid Hormones / Q000097:blood; D015029:Zeranol / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D004968:Estrogens, Non-Steroidal; D013963:Thyroid Hormones; D007334:Insulin-Like Growth Factor I; D015029:Zeranol; D009584:Nitrogen