Animal Breeding and Genetics Research Programs

Develop and maintain a program of research and graduate training in quantitative genetics with emphasis on sheep and beef cattle breeding and management of livestock genetic resources.

Major Activities Underway:

Selection to reduce seasonality of breeding in sheep
Evaluation of genetic resistance to internal parasites in sheep
Development of strategies for management of livestock genetic resources

Progress (last 5 years):

In research on selection to reduce seasonality of breeding, which was initiated in 1988, fertility of adult ewes in May and June increased from about 50% initially to about 85% in the last 4 years.  Cumulative genetic trends total about 20% for spring fertility, suggesting that about half of the observed progress is genetic and about half is environmental or adaptational.  A significant number of selected ewes do not exhibit a seasonal anestrus.  Fertility of 7-month-old ewe lambs in spring, however, remains low and has not responded to selection.  We have validated protocols for assessing resistance using a fixed dose of infective larvae of Haemonchus contortuos.  The protocol allows assessment of resistance without producing serious disease symptoms and can be integrated into normal flock management.  This project ended in summer, 1999.  Work with livestock genetic resource management involves consulting arrangements with the Food and Agriculture Organization of the United Nations and various other U.S. assignments and publications.

Cooperative Work:

At Iowa State University (Dr. Max Rothschild), DNA from animals in our selection lines was used to discover two polymorphic sites within the sheep melatonin receptor gene (Messer et al., 1997), In cooperative work with Utah State University (Dr. Noelle Cockett), a DNA repository was established in 1997 for our sheep lines.  DNA from all animals in the flock and from subsequent replacements was collected.  Animals were genotyped for the melatonin receptor polymorphism identified by Iowa State.  Relationship of this polymorphism to fertility and circulating levels of melatonin and prolactin are being evaluated.  In cooperation with INRA, France (Dr. Philippe Chemineau), nighttime blood samples were collected in summer, 1998 from ewes in our sheep lines and assayed at INRA for circulating melatonin and prolactin levels.  The select and control lines differed in circulating levels of both hormones.  Cooperating with the National Sheep Improvement Association, we developed the first across-flock genetic evaluations for the American sheep industry, in the Targhee, Suffolk, and Polypay breeds.  This effort included estimation of genetic parameter and adjustment factors for each breed and calculation of across-flock EPDs.

Future Plans:

The last lamb crop from the project to reduce seasonality of breeding was produced in fall, 1998.  The control line has been discontinued.  The selection line and a sample of low breeding value ewes were retained to further characterize selected ewes.  In spring, 1999, about one third of the flock was mated to Polypay rams to compare our ewes to daughters of industry rams.  Animals in the selected line are showing negative effects of narrowing of the genetic base and inbreeding, and need to be revitalized if the animals are to have an impact on the industry.  This project will probably completely terminate in 1 to 2 years.  We are interested in evaluation of hair sheep germplasm and development of hair sheep composite lines.  These wool-free, fertile, "easy-care" sheep would have a place in the industry if growth and muscling could be improved through  crossbreeding and selection.  Ideally, a hair sheep development project would replace the project to reduce seasonality.  We would like to continue to serve as a research and development center for the National Sheep Improvement Program (NSIP).  However, NSIP ceased processing records in spring, 1999 pending establishment of a new processing center, and its future is in doubt.  Involvement in genetic resource management activities is expected to continue.

 A senior faculty member in a commodity department at a comprehensive land-grant university should have a program with state, regional, national, and international visibility.  My program is general rather than specific and dynamic rather than static.  This approach is logical because the thrust of the program is problem oriented and involves both basic and mission-oriented research in poultry genetics and behavior.  Graduate education and undergraduate independent studies are important aspects of this research effort.

Major Activities Underway:

 Research involves the effects of selection on growth, reproduction, and behavior of chickens.  Genotype by environment interactions are evaluated by physiological and immunological responses during various phases of the life cycle.

Progress (past 5 years):

 Progress is difficult to ascertain because an academic position in this research area involves gradual accumulation of achievements rather than the spectacular.  Evaluation of progress during the past five years may be made by a review of research publications provided in the faculty vitae.

Cooperative Work:

 Because the research program is problem oriented, cooperation with other investigators is routine.  These investigators are from within the department, other departments at Virginia Tech, as well as other universities and institutes nationally and internationally.  Evidence for this cooperation is readily available from coauthorships in the research publications provided in the faculty vitae.

 The major goals of my research program are to identify and characterize genes which play important roles in regulating growth and reproduction in agriculturally important animals.  We are applying the tools of molecular biology to study the genomic organization and regulation of expression of these genes.

 Major Activities Underway:

 There are two major projects in my lab.  One project involves an analysis of the molecular mechanism that regulates expression of the turkey prolactin gene. Prolactin plays an important role in the transition of hens from egg laying to the incubation phase, thus understanding the regulation of prolactin gene expression is important for optimizing turkey reproduction.  The second project involves the cloning and characterization of intestinal peptide transporters.  Peptide transporters transport amino acids as short peptides across the intestine and thus are important nutritional regulators.

Progress (past 5 years)

  My lab has cloned the cDNAs and genes encoding turkey prolactin and the transcription factor, Pit-1. In mammals Pit-1 activates the prolactin gene.  We have found in turkeys that although Pit-1 can activate the turkey prolactin gene in vitro, it does not play a role in the in vivo regulation of the prolactin gene because Pit-1 and prolactin are not coexpressed in turkey lactotrophs.

 In collaboration with K.E. Webb, Jr., my lab has cloned cDNAs encoding the peptide transporter, PepT1, from sheep, pig, and chicken.  We have determined that PepT1 mRNA is expressed predominantly in intestinal tissue.  We are in the process of determining the substrate specificities of the cloned PepT1 after injection of PepT1 RNA into Xenopus laevis oocytes and measurement of proton cotransport by electrophysiology.

Cooperative Work:

 The PepT1 project is a collaborative effort between K.E. Webb, Jr., and
J.R. Bloomquist (Entomology).  I have collaborated with M. Akers (Dairy Sci) on the generation of transgenic mice overexpressing ovine IGF-I in the mammary gland.  In addition, I have been involved in a group project with B. Wentworth (U. WI), J. Proudman (USDA-Beltsville), and M. El Halawani (U. MN) on the development of transgenic turkeys by transfection of primordial germ cells.

Future Plans:

  We plan to continue our work on identifying transcription factors which regulate expression of the turkey prolactin gene and characterizing the substrate specificities of our cloned chicken, pig, and sheep PepT1 cDNAs.  We also plan to examine the developmental and nutritional changes in the expression of intestinal PepT1.
 

 Improve pork production efficiency
 Improve academic advising of undergraduates

Major activities underway:

NC-200 regional project “Integration of quantitative and molecular technologies for genetic improvement of pigs”.  Specifically, we are working on Objective 3: Improve the accuracy of predictors of progeny performance when applied to different breed combinations and environments.  White cross sows at the Swine Center were bred to paired Hampshire boars evaluated for litter size (High-EPD and Low-EPD).  Up to three gilts were kept from each resulting litter for two parities to determine actual litter size for comparison to EPD predictions.  The first set of sows completes their second parity in May.  Several more groups will complete the study by the end of the year.  We are beginning  the second phase of the objective, which is to determine how well TSI (Terminal Sire Index) predicts progeny performance.

 Improvement of pork quality through the use of ultrasonic evaluation of body composition.  This on-going Extension effort is used to demonstrate how objective measurements of fat and lean can benefit youth exhibitors and adults alike.  Results on show pigs are immediately available to exhibitors and their families.  Regression analysis will be used to determine changes in pigs over time.

 Activity in this area centers around student success once they enroll at Virginia Tech.  Student data have been analyzed for relationships between intervention activities and student performance in freshman chemistry.  In addition, high school demographics have been analyzed to find predictors of success in chemistry.  We currently are looking at the role of predictors in counseling students out of chemistry their first year.  In addition, outcomes assessment mandates that we collect data on current students and graduates.

Progress (past 5 years):

 Data from first parity sows shows a trend for daughters sired by high-EPD boars to have larger litters than those sired by low-EPD boars.  The difference is not statistically significant, however.

  Preliminary results from one youth show indicate a decrease of 2.5 mm in backfat for each year scanning has been used.

 Cooperative work:

NC-220 includes participants from almost all U. S. universities doing swine genetic research.  That list includes AL, IA, NC, NE, OH, OK, GA, IN, VA, and NC A&T.

Pigs used in the genetic research are also available for use in many other research projects and teaching activities.

Future plans:

Continue with these two long-range projects.