J. Anim Sci.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Head, W. A.
Right arrow Articles by Stellflug, J. N.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Head, W. A., Jr
Right arrow Articles by Stellflug, J. N.

Journal of Animal Science, Vol 74, Issue 9 2152-2157, Copyright © 1996 by American Society of Animal Science

JOURNAL ARTICLE

Effect of selection for lifetime production of lamb weaned on hormonal factors that affect growth in Targhee ewes and lambs

W. A. Head Jr, P. G. Hatfield, D. M. Hallford, J. A. Fitzgerald, M. K. Petersen and J. N. Stellflug
New Mexico State University, Las Cruces 88003, USA.

Targhee ewes (n = 22, average age 5 yr) rearing twin lambs were used to investigate serum growth hormone (GH), IGF-I, triiodothyronine (T3), thyroxine (T4), and prolactin (PRL; ewes only) concentrations associated with selection pressure for lifetime production of kilograms of lamb weaned per ewe. Period 1 started on d 4 after birth and was conducted in confinement. Periods 2, 3, and 4 were conducted on fenced intermountain sagebrush-bunchgrass range starting at an average of 49, 84, and 112 d after birth, respectively. Blood samples were collected hourly for 6 h on d 4, 11, 18, 25, 49, 84, and 112 after lambing. Ewe models included the fixed effect for line, with ewe age, lambing date, and starting weight nested within line as potential covariables.Lamb models included fixed effects for line, sex, and sibling sex, with lamb age and birth weight nested within line tested as possible covariables. Growth hormone concentrations were greater (P = .06) for selected than for control ewes, but lamb GH concentrations did not differ (P = .90) between selected and control lambs. Ewe prolactin concentration tended (P = .13) to be greater for control than selected ewes. Ewe and lamb IGF-I did not differ (P > .55) between selected and control ewes and lambs. Ewe T3 and T4 concentrations did not differ (P > .19) between selected and control ewes; however, lamb T3 and T4 concentrations were greater (P < .01) for control than for selected lambs. Increased GH concentration in selected ewes seemed to be associated with greater milk production. Differences in selected and control lamb T3 and T4 concentrations could be an indicator of receptor sensitivity, metabolic activity, or seasonal reproductive transitions in ewe lambs.




HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1996 by the American Society of Animal Science.