Latvijas Lauksaimniecības universitātes raksti nr. 18 (313) , 2007 ...

D. Jonkus, L. Paura Govju piena produktivitātes mainību ietekmējošo faktoru analīzeGovju piena produktivitātes mainību ietekmējošo faktoru analīzeAnalysis of Factors Affecting Cows Milk Productivity Traits VariationDaina JonkusLLU Agrobiotehnoloģijas institūts, e-pasts: Daina.Jonkus@llu.lvInstitute of Agrobiotechnology, LLU, e-mail: Daina.Jonkus@llu.lvLīga PauraLLU Vadības sistēmu katedra, e-pasts: Liga.Paura@llu.lvDepartment of Control Systems, LLU, e-mail: Liga.Paura@llu.lvAbstract. The research was organized in the training and research farm “Vecauce” of the Latvia Universityof Agriculture. The trials were conducted during pasture period and lasted for 30 days – from 13 July till11 August, 2001, and were repeated from 18 July till 16 August, 2002. The sample group included 70 clinicallyhealthy Latvian brown dairy cows in different lactations. The main research interest was paid to the analysisof the variations in cow milk productivity traits by assessing the influence of particular physiological factorsof an animal’s organism and that of environmental factors. Milk productivity traits with the highest valueof variation coefficient proved to be milk yield (Cv = 9.8 – 10.0%) and fat content (Cv = 8.8 – 11.2%).The protein content varied from 4.3 to 4.5%. The trait with the lowest variation was the lactose content(Cv = 2.1 – 3.9%), whereas milk yield and protein content showed the highest values of repeatability coefficient– r w= 0.73 – 0.84 and r w= 0.72 – 0.73 respectively. The content of fat and lactose were less stable exhibitingthe lowest coefficient of repeatability – r w= 0.32 – 0.50 and r w= 0.52 – 0.59 respectively. Between days of thepasture period, statistically significant fluctuations in milk yield were observed under the influence of externalenvironmental factors (p