Analysis of factors affecting cows milk productivity traits variation
2007
Jonkus, D. | Paura, L.
The research was organized in the training and research farm Vecauce of the Latvia University of Agriculture. The trials were conducted during pasture period and lasted for 30 days - from 13 July till 11 August, 2001, and were repeated from 18 July till 16 August, 2002. The sample group included 70 clinically healthy Latvian brown dairy cows in different lactations. The main research interest was paid to the analysis of the variations in cow milk productivity traits by assessing the influence of particular physiological factors of an animal's organism and that of environmental factors. Milk productivity traits with the highest value of 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 - rw = 0.73-0.84 and rw = 0.72-0.73 respectively. The content of fat and lactose were less stable exhibiting the lowest coefficient of repeatability - rw = 0.32-0.50 and rw = 0.52-0.59 respectively. Between days of the pasture period, statistically significant fluctuations in milk yield were observed under the influence of external environmental factors (p is less than 0.05).
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