Holm, DE (PhD)

Dietmar Holm was raised in Hartbeespoort and qualified as veterinarian at the University of Pretoria in 1998. After spending five years in private practice, he returned to Onderstepoort in 2003 for an academic career in production animal medicine and obtained the degree MSc in Veterinary Science cum laude in 2006. He has published six peer-reviewed scientific papers and presented more than 20 scientific papers at local and international congresses. The candidate is actively involved in the veterinary community, where his passion is to promote the impact that veterinarians can have on food production.

In his thesis, Early determination of the reproductive potential of beef heifers using reproductive tract scoring, pelvimetry and transrectal ultrasonography, the promovendus presents the results of four observational studies in beef cattle, including a seven-year longitudinal study of a commercial Bovelder herd. Various multivariable methods were used to determine the most useful predictors and prognostic models of reproductive failure from data collected before the first breeding season started. The findings of these studies demonstrated that heifers with relatively low production potential can be identified before reproductive failure occurs; therefore, animals with inferior potential can be removed to optimise productivity of the farm. These studies included the first observational study of the association of pre-breeding reproductive tract scoring (RTS) with long-term performance of cows, and carefully analysed and described the strengths, weaknesses and limitations of this system. A new application of internal pelvis area data in heifers was developed as a predictor of calving difficulty, improving the sensitivity and specificity of previous methods while avoiding potential side effects of selection based on pelvis area. Further, a novel prognostic model was developed for reproductive failure, using transrectal ultrasonographic data collected on a single day; it was demonstrated for the first time that internal pelvis area data adds significantly to prognostic models for reproductive failure, using RTS or transrectal ultrasonography.

The results of this study have so far been published in one paper in an international journal and a further three papers have been submitted. This research is likely to have a significant impact on the beef cattle breeding industry by adding value to selection programmes to improve productivity of beef cattle operations.

Thesis title:
Early determination of the reproductive potential of beef heifers using reproductive tract scoring, pelvimetry and transrectal ultrasonography

Supervisor: Prof PN Thompson
Co-supervisor: Prof PC Irons
External co-supervisor: P rof M Nielen (Utrecht University, the Netherlands)
Internal examiner: Prof EC Webb
External examiners: Prof DG Renter (Kansas State University, USA), Prof JLMR Leroy (Antwerpen University, Belgium)

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Dr Dietmar Erik Holm