Luteinizing hormone concentrations in serum of postpartum beef cows injected with microencapsulated luteinizing hormone-releasing hormone analog.

A. J. Roberts, C. F. Chang, A. V. Schally, J. J. Reeves

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

Twenty-five cows were divided equally into five groups to determine whether [D-Trp6]-luteinizing hormone releasing hormone (LHRH-A) microencapsulated in poly (DL-lactide co-glycolide) would increase basal serum concentrations of LH during the postpartum period. On d 5 postpartum, cows were injected i.m. with 2 ml of vehicle alone (Group 1) or vehicle containing microcapsules calculated to release .4, 1.6, 6.4 or 25.6 micrograms LHRH-A per day for approximately 30 d (Groups 2, 3, 4 and 5, respectively). Cows were bled every 15 min for 4 h immediately before and after injection and every 15 min for 4 h at weekly intervals for the next 4 wk to evaluate serum profiles of LH. Estrus was determined by twice daily observations and confirmed by serum progesterone. More cows in Groups 2, 3, 4 and 5 exhibited pulsatile patterns of LH after LHRH-A injection than in Group 1 (P less than .06). More pulses of LH were observed after LHRH-A injection in Groups 4 and 5 than in Group 1 (P less than .01). Mean concentrations of LH within treatment groups did not change during the initial injection, except in Group 5. All cows in Group 5 had a surge of LH immediately after injection. The induced surge of LH in two cows in Group 5 cows resulted in progesterone profiles similar to those during a normal luteal phase. Days to first postpartum estrus were not different among the five treatment groups. Microencapsulated LHRH-A given at a dose estimated to release 25 micrograms LHRH-A/d was effective in elevating LH concentrations following injection. However, effectiveness of this hormonal treatment in shortening postpartum anestrus was not substantiated.

Original languageEnglish (US)
Pages (from-to)2730-2734
Number of pages5
JournalJournal of animal science
Volume67
Issue number10
DOIs
StatePublished - Oct 1989
Externally publishedYes

ASJC Scopus subject areas

  • Food Science
  • Animal Science and Zoology
  • Genetics

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