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The effect of blood urea nitrogen on reproductive performance of beef heifers on different levels of nitrogen supplementation
Dissertation (MMedVet)--University of Pretoria, 2013.
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| Format: | Thesis |
| Language: | English |
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University of Pretoria
2014
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| _version_ | 1867613482521722880 |
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| access_status_str | Open Access |
| author2 | Holm, Dietmar Erik |
| author_browse | Holm, Dietmar Erik |
| author_facet | Holm, Dietmar Erik |
| collection | Thesis |
| dc_rights_str_mv | © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MMedVet)--University of Pretoria, 2013. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/36790 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:36:51.203Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2014 |
| publishDateRange | 2014 |
| publishDateSort | 2014 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/36790 The effect of blood urea nitrogen on reproductive performance of beef heifers on different levels of nitrogen supplementation Holm, Dietmar Erik takula.tshuma@up.ac.za Lourens, Dirk Cornelius Fosgate, Geoffrey Theodore Tshuma, Takula Blood urea nitrogen (BUN) Bad odours Bonsmara heifers Ruminants UCTD Dissertation (MMedVet)--University of Pretoria, 2013. Ruminants have a unique ability to acquire protein from non-protein nitrogen (NPN) sources, and to recycle nitrogen back into the rumen, instead of excreting all of it via the urine, faeces and milk. However, a high concentration of blood urea nitrogen (BUN) has a negative influence on conception. Additionally, a high dietary nitrogen intake poses a challenge to the environment in the form of ammonia emissions, eutrophication and bad odours. This calls for strategies to reduce the environmental impact of livestock production. Variation exists in the ability of cattle to recirculate nitrogen between as well as within cattle breeds. The purpose of this study was to investigate the effects of BUN concentration on reproductive performance in beef heifers under different management systems in South Africa. Serum samples from 369 Bonsmara heifers were taken in November and December 2010 to determine the BUN concentrations prior to the onset of the breeding season. Heifers were from five herds with different levels of protein supplementation during the weeks before the commencement of the breeding season. Body mass, age, body condition score (BCS) and reproductive tract score (RTS) were recorded at the same time as BUN concentration. Trans-rectal ultrasound and/or-palpation was performed four to eight weeks after the three-month breeding season to detect and estimate the stage of pregnancy. Days to pregnancy (DTP) was defined as the number of days from the start of the breeding season until a heifer was successfully mated. Logistic regression and Cox proportional hazards survival analysis were performed to estimate the effect of BUN concentration on subsequent pregnancy and DTP respectively, while stratifying by herd and adjusting for potential confounders. The correlations between BUN concentration, BCS and RTS were estimated using Spearman’s rho. Pearson correlations were used for the normally distributed variables of age and body mass. BUN concentration was not a significant predictor of pregnancy status but was a significant (P = 0.007) and independent predictor of DTP in heavily and some moderately supplemented herds. As BUN concentration increased, DTP also increased [hazard ratio (HR) = 0.827; 95% CI: 0.721 – 0.949; P = 0.007], while the chance of becoming pregnant decreased, although this was not statistically significant [odds ratio (OR) = 0.882; 95% CI: 0.772 – 1.007; P = 0.063]. Bonsmara heifers with higher BUN concentration, which suggests a better ability to recirculate nitrogen, might be at a disadvantage when the production system includes high levels of RDP supplementation because of this negative impact on reproductive performance. It is proposed that production systems be adapted to avoid selection against animals with an improved ability to recirculate nitrogen. gm2014 Production Animal Studies Unrestricted 2014-02-26T11:18:34Z 2014-02-26T11:18:34Z 2013-09-06 2013 Dissertation Tshuma, T 2013, The effect of blood urea nitrogen on reproductive performance of beef heifers on different levels of nitrogen supplementation, MMedVet dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/36790> E13/9/1129/gm http://hdl.handle.net/2263/36790 en © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | Blood urea nitrogen (BUN) Bad odours Bonsmara heifers Ruminants UCTD The effect of blood urea nitrogen on reproductive performance of beef heifers on different levels of nitrogen supplementation |
| title | The effect of blood urea nitrogen on reproductive performance of beef heifers on different levels of nitrogen supplementation |
| title_full | The effect of blood urea nitrogen on reproductive performance of beef heifers on different levels of nitrogen supplementation |
| title_fullStr | The effect of blood urea nitrogen on reproductive performance of beef heifers on different levels of nitrogen supplementation |
| title_full_unstemmed | The effect of blood urea nitrogen on reproductive performance of beef heifers on different levels of nitrogen supplementation |
| title_short | The effect of blood urea nitrogen on reproductive performance of beef heifers on different levels of nitrogen supplementation |
| title_sort | effect of blood urea nitrogen on reproductive performance of beef heifers on different levels of nitrogen supplementation |
| topic | Blood urea nitrogen (BUN) Bad odours Bonsmara heifers Ruminants UCTD |
| url | http://hdl.handle.net/2263/36790 |