초록
For this study three types of block such as medicated urea-molasses-mineral block (MUMMB, 7% urea), urea-molasses-mineral blocks ($UMMB_a$ 7% urea) and urea-molasses-mineral blocks ($UMMB_b$ 21% urea) were prepared. Naturally infested 24 indigenous dairy cows with gastrointestinal nematodes were used to study the effect of MUMMB, $UMMB_a$ and $UMMB_b$ on different parameters (body weight, milk yield, serum urea level, milk urea level). The cows were offered normal diet added with 250 g block per cow for every day. Straw and green grasses were used as basal diet in the ration. The managemental facilities for all cows of each group were similar. Cows were stall fed, calves were tied up at night and had free access to their dam during day time. Milking was done once daily in the morning. The daily average live weight gains by MUMMB, $UMMB_a$, $UMMB_b$, and control group (no block) were 52.08 g, 44.44 g, 48.58 g, and 1.41 g respectively. The live weight gain were statistically significant (p<0.01) in comparison to control group. The highest daily milk yield was observed in MUMMB treated cows (2.39 L/d); followed by $UMMB_b$ treated cows (1.82 L/d) and $UMMB_a$ treated cows (2.16 L/d). The lowest milk yield was found in control group (1.54 L/d). This result differs significantly (p<0.05) between treated groups and also with control group. During urea-molasses-mineral blocks $UMMB_a$, $UMMB_b$ licking milk urea level increased from initial $22.76{\pm}2.35mg/dl$ to $35.46{\pm}4.80mg/dl$ and initial $22.86{\pm}2.96mg/dl$ to $40.66{\pm}0.87mg/dl$ respectively. This variation of milk urea level was statistically significant (p<0.001). Similarly during $UMMB_a$, and $UMMB_b$ blocks licking, serum urea level increased in both treated groups from initial $22.76{\pm}2.60mg/dl$ to $32.68{\pm}2.21$ and initial $23.70{\pm}2.78mg/dl$ to $40.48{\pm}3.24mg/dl$, respectively. This variation of serum urea level was also statistically significant (p<0.001). Use of MUMMB instead of UMMB was proved better for milk production and live weight gain in dairy cows under the village condition of Bangladesh where balanced ration for dairy cows are a major scarcity. And various concentration of urea in blocks positively affect milk and serum urea levels of indigenous dairy cows.