Department of Animal Sciences research and reviews: beef and sheep

Relationship of a PCR-SSCP at the Bovine calpastatin locus with calpastatin activity and meat tenderness / H. Y. Chung, M. E. Davis, H. C. Hines, and D. M. Wulf -- Effects of calpain proteolysis and calpain genotypes on meat tenderness of angus bulls / H. Y. Chung, M. E. Davis, H. C. Hines, and D. M. Wulf -- Identification of genetic markers for growth and carcass traits in beef cattle / W. Ge, M. E. Davis, H. C. Hines, and K. M. Irvin -- Relationships of polymorphisms in the bovine leptin gene with differences in beef carcass traits / K. Tessanne, H. C. Hines, and M. E. Davis -- Effects of rate of gain during periods of restricted intake on performance and carcass characteristics in steers fed to achieve step-wise increases in rate of gain / J. E. Rossi and S. C. Loerch -- Effects of feeding regimen and days fed on performance and carcass characteristics of feedlot steers / J. E. Rossi, S. C. Loerch, S. J. Moeller, and J. P. Schoonmaker -- Effect of an accelerated finishing program on performance and carcass characteristics of early weaned bulls and steers / J. P. Schoonmaker, S. C. Loerch, F. L. Fluharty, T. B. Turner, S. J. Moeller and J. E. Rossi -- Yeast-mineral mixes and beef-cattle performance in fescue-based grazing systems: preliminary report / S. Boyles, W. Shriver, and D. Kobs -- Forage and animal evaluation of heifers at Indian Lake Hydrologic Unit CRP stocker grazing demonstration / S. L. Boyles, B. W. Stoll, and T. L. Dobbels -- Beef quality is every cattleman's business: education program / J. Yates and S. Boyles -- Effects of pelleted alfalfa and whole-shelled corn combinations on lamb growth and carcass characteristics / F. L. Fluharty -- Effects of feeding pelleted, ensiled, or a combination of pelleted and ensiled alfalfa on lamb growth and carcass characteristics / F. L. Fluharty, G. D. Lowe, and D. D. Clevenger -- Effects of corn silage vs. alfalfa haylage on lamb growth and carcass characteristics in forage-based finishing systems / F. L. Fluharty, G. D. Lowe, and D. D. Clevenger -- Effects of feed-delivery system and corn processing on lamb growth and carcass characteristics / F. L. Fluharty, G. D. Lowe, and D. D. Clevenger -- Effects of pen floor type and bedding on lamb growth and carcass characteristics / F. L. Fluharty, G. D. Lowe, and D. D. Clevenger -- A PCR-SSCP polymorphism detected in the 5' flanking region of the ovine IGF-I gene / A. Yilmaz, M. E. Davis, and H. C. Hine

Production of transgenic calves expressing an shRNA targeting myostatin

Myostatin (MSTN) is a well-known negative regulator of muscle growth. Animals that possess mutations within this gene display an enhanced muscling phenotype, a desirable agricultural trait. Increased neonatal morbidity is common, however, resulting from complications arising from the birth of offspring with increased fetal muscle mass. The objective of the current research was to generate an attenuated MSTN-null phenotype in a large-animal model using RNA interference to enhance muscle development without the detrimental consequences of an inactivating mutation. To this end, we identified a series of short interfering RNAs that demonstrated effective suppression of MSTN mRNA and protein levels. To produce transgenic offspring capable of stable MSTN suppression in vivo, a recombinant lentiviral vector expressing a short hairpin RNA (shRNA) targeting MSTN for silencing was introduced into bovine fetal fibroblasts. These cells were used as nucleus donors for somatic cell nuclear transfer (SCNT). Twenty blastocysts were transferred into seven recipient cows resulting in five pregnancies. One transgenic calf developed to term, but died following delivery by Caesarean-section. As an alternative strategy, microinjection of recombinant lentiviral particles into the perivitelline space of in vitro-produced bovine zygotes was utilized to produce 40 transgenic blastocysts that were transferred into 14 recipient cows, resulting in 7 pregnancies. Five transgenic calves were produced, of which three expressed the transgene. This is the first report of transgenic livestock produced by direct injection of a recombinant lentivirus, and expressing transgenes encoding shRNAs targeting an endogenous gene (myostatin) for silencing. © 2011 Wiley Periodicals, Inc

Development of Transgenic Livestock with Reduced Myostatin Expression Using Rna Interference

RNA interference (RNAi) is a means of regulating gene expression by targeting mRNA in a sequence-specific manner for degradation or translational inhibition. Short hairpin RNAs (shRNAs) and siRNAs have been extensively employed for manipulating gene expression in a wide range of species. However, the great majority of this work has involved in vitro studies with cells grown in culture. Our goal for this project is to produce transgenic livestock in which myostatin, a negative regulator of muscle growth, has been targeted for silencing by RNAi. In theory, livestock in which myostatin has been silenced should exhibit increased muscle growth and development. To that end, we designed shRNAs to target the bovine myostatin mRNA sequence. The shRNAs were cloned into a lentiviral vector that contains a cytomegalovirus promoter controlling green fluorescent protein and shRNA expression as well as neomycin resistance. Infective lentivirus was made in HEK293T cells through co-transfection of the lentiviral vector, a packaging plasmid, and a plasmid expressing the VSVG pseudotype. Bovine fetal fibroblasts were transduced, selected using Geneticin®, and nuclear transfer was utilized to produce cloned transgenic embryos. There were 186 fusion attempts resulting in 160 fused embryos (fusion rate = 86%). Of these, 54 reached the blastocyst stage (34%) and 10 embryos were transferred into 5 recipient females (2 embryos per recipient). At 40 days, ultrasound revealed 1 confirmed pregnancy. Current plans are to harvest this fetus at 90 days and analyze it for evidence of myostatin knockdown. The production of transgenic animals exhibiting myostatin knockdown through lentiviral-mediated RNAi will demonstrate the utility of RNAi in the study of gene function in large animal models without the need for homologous recombination techniques, which are currently inefficient in species other than mice