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University of Melbourne

1. Hancock, Andrew Stuart. Management practices and breeding soundness of dairy herd bulls in south west Victoria.

Degree: 2016, University of Melbourne

In pasture-based, seasonal calving dairy herds of south west Victoria, the mating period usually consists of an initial artificial insemination (AI) period followed by a natural mating period using herd bulls. Bull breeding soundness evaluations (BBSE) were performed on 256 bulls from 32 dairy herds in south west Victoria, according to the Australian Cattle Veterinarians (ACV) guidelines, prior to and immediately after a single natural mating period. At the time of evaluation a questionnaire regarding the management of the bulls was undertaken. The objectives of this study were: to describe the management practices of dairy herd bulls; to describe and quantify the causes of reduced fertility in local dairy herd bulls, as measured by the BBSE; to describe the causes of bull breakdown during mating; and to identify any possible associations between bull management practices and bull fertility via the pre- and post-mating BBSE. At the pre-mating BBSE 19.5% of bulls were classified as ‘High risk’ of reduced fertility. These classifications were mostly due to physical abnormalities and reduced semen quality. At the post-mating BBSE 36.5% of bulls were classified as ‘High risk’ of reduced fertility. These classifications were mostly due to physical abnormalities, of which lameness was the major problem. Of the bulls used 15.9% were reported to have been removed from the normal mating rotation by the herd manager, and lameness and injuries were the cause of almost all of these breakdowns. To identify bull and herd-level factors associated with being classified as ‘High risk’ at the pre-mating and post-mating BBSE respectively, multivariable mixed effects logistic regression models were constructed. Bulls older than 4 years of age were more likely to be classified ‘High risk’ compared with bulls less than 4 years of age at the pre-mating BBSE. Herds which fed their bulls grain prior to mating were more likely to have a higher proportion of bulls classified as ‘High risk’ at the post-mating BBSE. Univariable analyses also highlighted some areas for potential further research, including breed differences between dairy bulls, leg conformation and joint abnormalities, preventative hoof blocking for bulls, and mating ratios. In general, the understanding of the use of dairy herd bulls in Australian and overseas dairies would benefit from more research. The presence of infectious reproductive disease pathogens in these bulls was also investigated. Dairy herd bulls from the 32 herds were sampled for bovine viral diarrhoea virus (BVDV) (256 bulls, 32 herds) prior to the natural mating period, bovine herpes virus 1(BHV-1) prior to (10 bulls, 5 herds) and after (118 bulls, 19 herds) the natural mating period, and for Campylobacter fetus spp. and Tritrichomonas foetus after the natural mating period (61 bulls, 7 herds). BVDV was detected from an ear-notch sample using a commercially available rapid assay ELISA, BHV-1 and T. foetus were screened for by PCR from a penile swab and preputial sample respectively, and C. fetus spp. were…

Subjects/Keywords: dairy herd bull; bull breeding soundness evaluation; lameness; bovine herpes virus; bovine viral diarrhoea virus; Campylobacter fetus; Tritrichomonas foetus; venereal disease

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APA (6th Edition):

Hancock, A. S. (2016). Management practices and breeding soundness of dairy herd bulls in south west Victoria. (Masters Thesis). University of Melbourne. Retrieved from http://hdl.handle.net/11343/91706

Chicago Manual of Style (16th Edition):

Hancock, Andrew Stuart. “Management practices and breeding soundness of dairy herd bulls in south west Victoria.” 2016. Masters Thesis, University of Melbourne. Accessed December 01, 2020. http://hdl.handle.net/11343/91706.

MLA Handbook (7th Edition):

Hancock, Andrew Stuart. “Management practices and breeding soundness of dairy herd bulls in south west Victoria.” 2016. Web. 01 Dec 2020.

Vancouver:

Hancock AS. Management practices and breeding soundness of dairy herd bulls in south west Victoria. [Internet] [Masters thesis]. University of Melbourne; 2016. [cited 2020 Dec 01]. Available from: http://hdl.handle.net/11343/91706.

Council of Science Editors:

Hancock AS. Management practices and breeding soundness of dairy herd bulls in south west Victoria. [Masters Thesis]. University of Melbourne; 2016. Available from: http://hdl.handle.net/11343/91706

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