. Fourteen lactating Friesian cows were used. 7 cows as control injected
subcutaneously with saline (0.9% Nac!) and the rest were injected subcutaneously
with 500 mg rbST (Somatech®) at injection intervals of 14 days. Blood and milk samples were taken every two weeks for analysis. Milk
constituents such as fat. total protein. lactose, total solids, solids not fat and somatic
cell count were determined. Fresh blood used for the determination of hemoglobin
(Hb) and hematocrit (HT). Blood constituents (total protein, albumin, globulin, total
lipids, triglycerides and glucose were determined in plasma colorimetrically. Results
are summarized as follow: Injection of rbST causes insignificant increase In both Ht
(%) and Hb (g/dl) of the whole blood by 2.6% and 1.4%, respectively over the control.
Hb concentration was higher in injected cows' plasma blood at 3rd, 4th, 7th and 10th
injections. Concentrations of plasma tolal protein (g/dl), globulin, triglycerides (mg/dl)
and the ratio between albumin and globulin were significantly (P<0.05) higher by 5.9
%, 13.1 %, 11.1 % and 3.8 %, respectively, while plasma albumin was lower in blood of
rbST injected cows by 0.7%, than the control cows. Meanwhile, concentraticn of
plasma total lipids (gIL) was slightly higher in blood of rbST injected cows than control
bv..0.5%. Total protein concentration was higher in treated cows at 1st, 2nd, 3rd, 5th.
6th and 7th injections. Milk yield at 305 days was higher (P<0.05) in rbST treated cows than control
by 20.6%. Injection of rbST in Friesian cows had significantly higher milk protein than
control by 2.4%, it was significantly higher at 1 st, znc, 3rd, 4th, 5th, 7th, 8th, 9th and
10th injections. Cows injected with rbST were inSignificantly higher in milk fat and total
solids, but lower in milk lactose than control cows by 11.1 %, 9.4 % and 0.2%,
respectively. Changes in milk somatic cell count revealed that control cows had lower
(P<0.05) counts than rbST treated cows by 30.6 %.