THE EFFECT OF RECOMBINANT BOVINE SOMATOTR OPIN (RBST) ON PRODUCTION AND SOME COMPONENTS OF MILK IN COWS OF THE CZECH PIED BREED

A test of the rBST effect was conducted in 18 cows of the Czech Pied b reed in the first lactation in the months of January to February 1993. The cows were in the 117th to 201st day of pregnancy. They were evenl y divided into an experimental and control group according to the time from calving, pregnancy duration, milk and fat production over 200 an d/or 100 lactation days, daily milk production within three months bef ore the trial and two controls in a week before rBST treatment. The pr eparation rBST was subcutaneously implanted into the skin fold on the neck to nine experimental cows (Optiflex, at a single dose of 640 mg S emidobove, manufactured by the company Eli Lilly, S. A., Geneva). Cont rol cows were administered a dose of 5 ml physiological solution in th e same way and on the same date. Milk production of cows was determine d twice a week, on Monday and Thursday, milk samples were taken during morning milking on the same days. Milk samples were analyzed for the content of fat, total proteins, lactose monohydrate and solids-not-fat . The RIA technique was used to determine progesterone in whole milk. The effect of rBST treatment was investigated on the basis of comparin g average daily milk yields, milk components and progesterone levels o f the experimental and control cows on the particular control days, ap plying a one-way classification analysis (GLM procedure SAS - Statisti cal Analysis System program). The objective of the test was to verify the effect of rBST with protracted effect on milk production, milk com ponents and progesterone concentrations in cows of the Czech Pied bree d, among other things to verify the effect of the preparation used by Zaoral et al. (1993) in their study. Milk production of the experiment al cows increased on average by 31.4 kg, i.e. by 12% (Tab. I), after t reatment within die 28-day period. The more marked increase in milk pr oduction was significant at P < 0.05 to P < 0.01 in fifty percent of r ecorded yields in the first fortnight. In the second fortnight, the di fferences were smaller, statistically insignificant. The average milk production of the experimental cows was higher than that of the contro l cows throughout the whole experimental period (Fig. 1). There were n o significant differences (P > 0.05) in the milk components (Tab. II) between the experimental and control animals. On two control days only , the difference in fat percentage was significant (P < 0.05) in favor of the control cows, once in lactose level in favor of the experiment al group. The progesterone level was insignificantly higher (P > 0.05) in the cows of control group (Tab. III).