Changes in metabolites and metabolic hormones during the first 12 weeks postpartum in both summer and winter were analyzed on a total of 18 lactating, Holstein cows (summer, n=11; winter, n=7). The summer trial covered the months of August through October. The winter trial began in November and lasted through early February. Maximum and minimum temperature and humidity values were recorded daily. Blood was sampled in serum, fluoride and heparin tubes from the coccygeal vein once a week beginning at day of calving for 12 weeks. Concentrations of progesterone, cortisol, thyroxine, leptin, NEFA, cholesterol and insulin were analyzed from serum samples. The metabolites glucose, PUN and â-HBA were analyzed with plasma collected from fluoride and heparin containing tubes. No significant seasonal differences were found between summer and winter calving groups for P4, T4, glucose, insulin, PUN and NEFA. However, leptin (P < 0.01), cholesterol (CHL) (P < 0.0001) and â-HBA (P < 0.0001) had significant seasonal differences between the two calving groups. The mild heat stress during the early part of the summer trial may not have been severe enough to detect significant changes in serum T4 or the animals had become acclimated to these temperatures. Summer calving cows may have experienced a drop in feed intake at calving (not measured) enough to increase their plasma ketone bodies (â-HBA), but not enough to dramatically reduce circulating levels of glucose and insulin.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-07312003-174200 |
| Date | 01 August 2003 |
| Creators | Nordbladh, Louise I. |
| Contributors | Dr. Scott Whisnant |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-07312003-174200/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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