Postpartum LH and GH secretory patterns were evaluated with mature Brangus cows group fed either 50%M (n = 8) or 100%M (n = 7) NRC maintenance energy requirements starting two months prepartum and continuing for three months postpartum. Feed level was adjusted at 14 day intervals. Weights of cows and (or) calves were taken every 14 days before and after calving. Sequential blood samples were taken every 15 min for 8 h at biweekly intervals starting 14 days postpartum and continuing until 100 days. Serum LH and GH were determined by a validated double antibody RIA. A peak-detection algorithm was used to summarize hormone data into 5 variables for each cow at each bleeding period. Data were analyzed by GLM and regression using SAS procedures. Cows in the 100%M group were heavier (P<0.01) at calving time and at the end of the trial. There were no significant differences for weight of calves at birth or at the end of the study for the two energy levels. Total release of LH during secretory episodes was 5 fold greater (27 vs 5 ng/ml x min P<0.05) in cows receiving 100%M vs 50%M energy. Basal concentration and peak height of LH increased linearly with time postpartum in 50% but not 100% energy groups. For GH, cows receiving 50%M energy had more secretory spikes (2.6 vs 2.1 per 8 h; P<0.05), and higher basal concentration (14 vs 8 ng/ml; P<0.05), and a shorter duration of secretory episodes (82 vs 95 min; P<0.05) compared with cows on 100%M energy. Maximum release of GH occurred earlier postpartum in cows receiving 100%M energy (30-39 d) vs cows receiving 50%M energy (90+d). Number of GH peaks increased linearly with time postpartum in cows on 100% energy, but not in the 50% group. Dietary energy restriction of mature beef cows significantly alters several parameters of LH and GH secretion during the early postpartum period.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/186008 |
| Date | January 1992 |
| Creators | Zapien, Antonio. |
| Contributors | Ray, Donald E., Wise, Mark E., Wegner, Thomas N., Rice, Richard W., Whiting, Frank M. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | text, Dissertation-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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