University of Natural Resources and Life Sciences, Vienna (BOKU) - Research portal
Gewählte Master / Diploma Thesis:
Christian Kolb
(2012):
Einfluss von Klimaelementen auf Milchparameter unter Bedingungen der Vollweidehaltung von Milchkühen.
Master / Diploma Thesis - Institut für Nutztierwissenschaften (NUWI),
BOKU-Universität für Bodenkultur,
pp 201.
UB BOKU
obvsg
- Abstract:
- The aim of this study was to investigate the influence of thermal stress in form of two temperature-humidity indices (THI) with consideration of temperature and relative humidity (Formula 1) and additionally wind speed and solar radiation (Formula 2) on milk parameters of grazing dairy cows. 3355 individual records for milk-, fat- and protein yield and somatic cell count (SCC) of 23 (2008) and 27 cows (2009) were collected between May and September on two research farms, located in a valley with continental climate. The greatest impact on milk yield was found for the number of hours above THI 72 on test day with -0.35 kg per hour increase (Formula 2, P<0.0001). Fat yield showed a maximum reduction of 0.015 kg per unit increase of average THI from respective to previous day (Formula 1, P<0.0001). Protein yield decreased by 0.023 kg per unit increase of mean THI above THI 72 on test day (Formula 1, P<0.05). Milk yield significantly declined at a threshold of eight hours above THI 72. Protein yield was affected earlier than fat yield. SCC was affected only by few THI variables, being most affected by the number of hours above THI 72 on the previous day resulting in an increase by 7.515 cells/ml per hour (Formula 2, P<0.01). A quadratic relationship for THI led to an increase in milk-, fat- and protein yield in lower THI ranges and at low number of hours per unit increase. A further increase of THI and hour led to a decline (inversely for SCC). Previous days had less impact with increasing distance to the test day and also had less impact than the average of THI variables over several days. Brown Swiss cows showed a smaller increase of milk, fat and protein yield with increasing THI than Holstein Friesian, but were affected earlier and more strongly than Holstein Friesian (inversely for SCC). Critical THI values were only rarely observed, but the results show that even in moderate climate zones an effect of thermal stress on milk parameters can be expected.
- Beurteilende(r): Winckler Christoph
- 1.Mitwirkender: Knaus Wilhelm Friedrich