HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Rhodes, R. C. Articles by Long, C. R. Search for Related Content PubMed PubMed Citation Articles by Rhodes, R. C., III Articles by Long, C. R.

Corpus Luteum function in the Bovine: in Vivo in Vitro Evidence for Both a Seasonal and Breedtype Effect^{1 , 2,}

Texas A&M University Agricultural Research and Extension Center, Overton 75684

Abstract

Breed type and season appear to modify the reproductive capacity of cattle. This study was designed to elucidate the effect of these factors on the bovine corpus luteum. Six Brahman (B) and six Hereford x Holstein (H) heifers were bled via coccygeal vessel puncture on d 2, 4, 6, 8, 10, 12 and 13 postestrus within 20 d of both the summer and winter solstices. On d 13 postestrus, the corpus luteum (CL) was surgically removed from each heifer following blood sampling. Serum progesterone, total progesterone content of each CL and in vitro progesterone (P₄) production of dispersed luteal cells was determined. Serum progesterone on d 2 through 13 did not vary with breedtype or season. However, the CL weights differed (P>.05) between breeds (H heavier than B), and there was a tendency for CL weight to be greater during the summer than winter among both B and H heifers. CL concentrations of P₄ (µg/g) also differed between B and H. Concentrations of P₄ in B were greater (P>.10) during winter than during summer, but H concentrations of P₄ did not differ between seasons. Total P₄ content was greater (P>.01) in the winter than in summer and in H than in B. Luteal cell viability did not vary with breedtype, season or LH dosage. Breedtype (P>.001) and season (P>.001) influenced the capacity of incubated luteal tissue to release progesterone in response to luteinizing hormone (LH). Luteal tissue from H released a greater amount of progesterone than incubated B tissue. Further, the release of progesterone by winter CL tissue in the LH-challenged cultures was diminished. The minimal LH dosage required to elevate P₄ above concentrations observed at 0 ng LH did not differ between breeds or seasons (5 ng LH). However, the amount of P₄ released at 5 ng LH dosage was highest for tissue from H during the winter, followed by H during the summer, B during the summer and B during winter. In contrast, maximal release of P₄ was associated with the 500 ng LH dosage for H (summer and winter), the 100 ng LH dosage for B during summer and the 50 ng LH dosage for B during winter. At LH dosages above 10 ng, P₄ concentrations were consistently greater in H than B, with summer greater than winter values in both breedtypes. The greatest change in P₄ release (highest P₄ concentrations minus P₄ concentration at 0 ng LH) followed the same trends as above. Significant (P>.001) interaction terms were also detected for breed X season and breed x dose. These data indicate that luteal tissue from H had a greater capacity to release P₄ in vitro than luteal tissue from B. Further, CL removed during the winter had a lessened capability to release P₄ than CL removed during the summer.

¹ Journal Paper TA 16937, Texas A&M Univ. Agr. Exp. Sta.

² This study was a contribution to the Western Regional Research Project, W-112, "Reproductive Performance in Domestic Ruminants".

³ Present address: Division of Anim. and Vet. Sci., West Virginia Univ., Morgantown 26506.

⁴ Dept. of Anim. Sci., Texas A&M Univ., College Station 77843.