This thesis described the results of two studies that measured the concentrations of serum micronutrients in western Canadian beef cows at key production points, and examined associations between reproductive outcomes and micronutrient concentrations. The first study reported the serum copper and molybdenum concentrations at pregnancy testing time in cows from 66 cow-calf herds that were enrolled in a study of factors affecting productivity in 205 herds from western Canada. A relatively small proportion of cows had serum copper and molybdenum concentrations outside of adequate levels (16.2% of cows had below adequate serum copper, < 0.60 ppm; 12% of cows had high serum molybdenum, > 0.10 ppm). There were no associations between copper and molybdenum concentrations measured at the end of the grazing season and reproductive outcomes measured in these cows, with the exception that cows with the lowest serum copper concentrations at pregnancy testing were more likely to be pregnant than cows with higher copper concentrations. The practice of comparing serum copper and molybdenum concentrations between pregnant and non-pregnant animals in the fall as a tool in investigating poor pregnancy rates was not supported by this study.
In the second study, serum micronutrient concentrations of beef cows (n = 791) in southern Saskatchewan were measured before placement onto summer grazing and breeding pastures and again at the end of the grazing season. Pre-breeding serum copper concentrations were less than adequate (< 0.60 ppm) in 75% of cows. High concentrations of serum molybdenum (d 0.10 ppm) were present in 19% of cows at pre-breeding. Cows < 10 years of age with lower pre-breeding serum copper concentrations were at increased odds of nonpregnancy. The greatest effect on pregnancy rates was observed for pre-breeding serum copper concentrations < 0.4 ppm. Season of measurement influenced the concentrations of serum micronutrients in these cows. Copper and vitamins A and E were higher in the fall, and molybdenum and selenium concentrations were lower in the fall.
These studies described serum micronutrient concentrations from healthy cows in western Canada at two production points, pre-breeding placement onto grazing pastures and pregnancy testing when cows are removed from grazing pasture. Identifying increased odds of nonpregnancy in cows with below adequate serum copper at pre-breeding emphasizes the importance of ensuring adequate copper concentrations in breeding females during this critical production phase.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-08122011-135644 |
| Date | 30 August 2011 |
| Creators | Van De Weyer, Leanne Margaret |
| Contributors | Waldner, Cheryl, Hendrick, Steve, Rosengren, Leigh, Stookey, Joe, Hill, Janet, Lardner, Bart |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-08122011-135644/ |
| 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 University of Saskatchewan 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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