[Seasonal changes in the concentration of total blood proteins in cows during various phase intervals]

In four one-year stages (A, B, C, D) in the summer (L) and winter (Z) feeding seasons, the total protein (CB) of blood plasma was determined in 3207 cows included in three groups: I - the first stage of lactation, II - the second stage of lactation, and III - the 8th to 9.5th month of pregnancy. 1948 cows were examined when given the winter feed rations and 1259 cows on the summer rations. At the same time, the supply of required digestible crude protein (SNL) and energy (starch units) was calculated for the feed rations of different groups of cows. High-pregnant cows (III) had the lower total protein in all the four years and feeding seasons, as compared with the groups of lactating cows. The difference was significant in nine out of ten cases in relation to group I and in eight cases in relation to group II. This is a regular phenomenon, independent of the summer or winter feed ration type and of the seasonal climatic effects of each year. The trend of decreasing crude protein levels with the length of lactation is less conclusive (significant in four out of ten cases); nevertheless, it is still apparent, since none of the three reverse cases was significant. The differences in total protein concentration between cows of different groups are absolute and their causes must be endogenous: they cannot be attributed to differences in the supply of required nutrients. A rise of total protein content was recorded in both feeding seasons at stages C and D in all groups of cows. The higher occurrence of hyperproteinaemia is ascribed to increased proteosynthesis at better utilization of the supplied crude protein. Relative (concentration) hyperproteinaemia was excluded. The effect of the summer or winter type of feed rations on total protein concentration was insignificant when considered for the whole four-year period; at individual stages significantly higher total protein values in the summer feeding season than in the winter feeding season were recorded three times and the reverse case was recorded only once.