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n Ondersoek na die invloed van monsteringsfrekwensie tydens melkaantekening op die betroubaarheid van prestasietoetsing by melkkoeie
Tesis (M. Sc. Agric.) -- Universiteit van Stellenbosch, 1995.
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| Format: | Thesis |
| Language: | Afrikaans |
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Stellenbosch : Stellenbosch University
2012
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| _version_ | 1867613934528233472 |
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| access_status_str | Open Access |
| author | De Waal, Hendrik Loock |
| author2 | Heydenrych, H. J. |
| author_browse | De Waal, Hendrik Loock Heydenrych, H. J. |
| author_facet | Heydenrych, H. J. De Waal, Hendrik Loock |
| author_sort | De Waal, Hendrik Loock |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Tesis (M. Sc. Agric.) -- Universiteit van Stellenbosch, 1995. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/54806 |
| institution | Stellenbosch University (South Africa) |
| language | Afrikaans |
| last_indexed | 2026-06-10T12:44:02.133Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/54806 n Ondersoek na die invloed van monsteringsfrekwensie tydens melkaantekening op die betroubaarheid van prestasietoetsing by melkkoeie De Waal, Hendrik Loock Heydenrych, H. J. Stellenbosch University. Faculty of AgriSciences. Dept. of Agricultural Economics. Milk yield Dairy cattle Dairy cattle -- Monitoring Dissertations -- Agriculture Tesis (M. Sc. Agric.) -- Universiteit van Stellenbosch, 1995. The purpose of this study was to investigate the possibility of simplifying the process of sampling during milkrecording, as well as to possibly decrease the frequency of milkrecording without affecting the accuracy of the calculated lactation milk yield (LMY), butterfat- (LBY), -protein- (LPY) and -lactose yield (LLY) over a 200 to 300 days lactation. The most important question was whether five weekly proportional, composed 24-hour sampling, as practised now, can be replaced with single evening sampling. Composite milksamples were obtained weekly at two Holstein-Fresian herds involving 129 cows and two Jersey herds involving 107 cows. A single evening and a single morning milksample were also taken from each cow. Daily sampling was not practicable. A composite weekly milksample was therefore considered the best estimate of production parameters. Although the frequency of milk recording was reduced from the present general four weekly cycle to five weeks, satisfactory accurate estimations of a cow’s production are still obtained. However, no other method is as accurate as daily milk recording. An important conclusion derived from the present investigation is that less frequent milk recording (five weekly or six weekly) should have no negative influence on the selection programme of a herd or breed. This is because less frequent milk recording has relative little influence on the ranking order of individual milk cows. Therefore, it should also have virtually no influence on the breeding values and thus on the ranking order of progeny tested bulls since progeny tests are based on 30 or more effective daughters per bull. The effect of increasing test intervals on accuracy were tested through regression and correlation analyses. It was proven that LMY (R² = 0.99), LPY (R² = 0.98) and LLY (R² = 0.99) could be estimated accurately through five weekly single evening milksamples, but not LBY (R² = 0.89). Correction factors must be used for the accurate estimation of LBY under a regime of five weekly single evening milksampling. Nevertheless, six weekly samples and milk recording could be practically applied as the economic importance of butterfat is much smaller than in the past. At present the price ratio of milk is 13:6 for protein:butterfat. The A.I. industry also uses component values based on a 13:6 ratio of the expected breeding value of progeny test bulls for protein and butterfat, respectively. Masters 2012-08-27T11:36:44Z 2012-08-27T11:36:44Z 1995 Thesis http://hdl.handle.net/10019.1/54806 af Stellenbosch University 220 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Milk yield Dairy cattle Dairy cattle -- Monitoring Dissertations -- Agriculture De Waal, Hendrik Loock n Ondersoek na die invloed van monsteringsfrekwensie tydens melkaantekening op die betroubaarheid van prestasietoetsing by melkkoeie |
| title | n Ondersoek na die invloed van monsteringsfrekwensie tydens melkaantekening op die betroubaarheid van prestasietoetsing by melkkoeie |
| title_full | n Ondersoek na die invloed van monsteringsfrekwensie tydens melkaantekening op die betroubaarheid van prestasietoetsing by melkkoeie |
| title_fullStr | n Ondersoek na die invloed van monsteringsfrekwensie tydens melkaantekening op die betroubaarheid van prestasietoetsing by melkkoeie |
| title_full_unstemmed | n Ondersoek na die invloed van monsteringsfrekwensie tydens melkaantekening op die betroubaarheid van prestasietoetsing by melkkoeie |
| title_short | n Ondersoek na die invloed van monsteringsfrekwensie tydens melkaantekening op die betroubaarheid van prestasietoetsing by melkkoeie |
| title_sort | n ondersoek na die invloed van monsteringsfrekwensie tydens melkaantekening op die betroubaarheid van prestasietoetsing by melkkoeie |
| topic | Milk yield Dairy cattle Dairy cattle -- Monitoring Dissertations -- Agriculture |
| url | http://hdl.handle.net/10019.1/54806 |
| work_keys_str_mv | AT dewaalhendrikloock nondersoeknadieinvloedvanmonsteringsfrekwensietydensmelkaantekeningopdiebetroubaarheidvanprestasietoetsingbymelkkoeie |