|HERGENREDER, JERILYN - Texas Tech University|
|LEGAKO, JARED - Utah State University|
|DIHN, THU T. - Mississippi State University|
|SPIVEY, KARI - Texas Tech University|
|BAGGERMAN, JESSICA - Texas Tech University|
|BECKETT, JOHN - Consultant|
|BRANINE, MARK - Zinpro Corporation|
Submitted to: Biological Trace Element Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2015
Publication Date: N/A
Interpretive Summary: Cattle producers are constantly seeking supplements to enhance the diets of feedlot animals to promote feedlot and carcass performance. Supplementation of zinc in the diet is important to maintain homeostatic conditions across multiple physiological and biochemical pathways. Therefore, the objective of this study was to determine the effect of supplementing zinc methionine(ZnMet) on feedlot growth performance, carcass characteristics, skeletal muscle and adipose tissue gene expression, protein synthesis, and fatty acid compositon of calf-fed Holstein steers. There were no differences observed in either feedlot or carcass performance. However cattle fed ZnMet did display an increase proteins and genes essential for the establishment of lean tissue deposition. Control cattle had a smaller skeletal muscle cross-sectional area and also were observed to have more internalized beta-receptors which means there ability to bind the beta-agonist was diminished. When fatty acids were quantified, it was determined that ZnMet increased neutral lipids , but not phospholipids concentrations which coinside with decreased expresion of certain fat producing enzymes in supplemented cattle. Overall, ZnMet increased myosin heavy chain expression and increased muscle hypertrophy; however, these changes did not translate to overall enhancement of feedlot and carcass performance, thereby leaving profitability unchanged. This information will be informative to producers, packers, pharmaceutical companies, and veterinarians. It is also important to researchers as they attempt to elucidate some of the biochemical interactions of trace minerals on gene expression and animal performance.
Technical Abstract: Calf-fed Holstein steers were supplemented with a zinc (Zn) methionine supplement (ZnMet; ZINPRO®; Zinpro Corporation, Eden Prairie, MN) for 115±5 days prior to harvest along with zilpaterol hydrochloride (ZH; Zilmax®; Merck Animal Health, Summit, NJ) for the last 20 days with a 3 day withdrawal to evaluate the effects on growth and carcass performance together with gene and protein expression of skeletal muscle, adipose tissue and fatty acid (FA) composition of polar and neutral lipid (PL and NL) depots. Steers (n=1,296; initial weight=468.5±0.5 kg) were sorted by weight, blocked by harvest date, and randomly assigned to pens (six/treatment) and treatment: Control (90 ppm Zn from ZnSO4) and ZnMet (Control plus 720 mg Zn from ZnMet/head/day). There were no differences (P > 0.05) in growth performance or carcass characteristics. Cattle fed ZnMet had an increased (P < 0.05) abundance of myosin heavy chain (MHC)-I mRNA in skeletal muscle tissue. Control cattle had an increased (P < 0.05) abundance of MHC-IIX, ß1-adrenergic receptor (ßAR), peroxisome proliferator-activated receptor gamma and stearoyl-CoA desaturase mRNA in skeletal muscle tissue. The ZnMet cattle had greater (P < 0.05) abundance of MHC-II protein, increased MHC-IIA and IIX cross-sectional areas (< 0.05), increased percentage of MHC-I fibers (P < 0.05) and tended (P < 0.10) to have a greater percentage of MHC-IIA fibers. Control cattle had a greater (P < 0.05) percentage of MHC-IIX fibers, nuclei density but less total muscle cells. There was a greater (P < 0.05) density of cells expressing Pax7, and tendency (P < 0.10) for a greater density of ß3AR and internalized ß2AR in ZnMet cattle. Control cattle had an increased (P < 0.05) density of ß2AR. An interaction was determined for several FA (14:0, 15:0, 16:0, 17:0, 18:0, 14:1, 16:1, 17:1, 18:1trans, 20:1, 18:2 n-6; P = 0.049), where ZnMet increased concentrations of NL FA, while PL FA were not impacted. Alteration in FA saturation was in agreement with decreased mRNA expression of stearoyl-CoA desaturase in ZnMet. The addition of ZnMet resulted in increased MHC-I and decreased MHC-IIX gene expression with increasing muscle hypertrophy and protein concentration.