Abstract:
The objective of the present experiment was to study the effect of dietary Na₂CO₃ supplementation on milk production, milk compositions, digestibility of nutrients and the concentration of electrolytes in plasma, urine and fecae in crossbred Friesian cows. Six multiparous crossbred Friesian cows, 114±24 d postpartum, were used in the experiment. They were randomly divided into three groups of two cows each. A Latin Square (3x3) design was used in this study. Each period lasted for 21 days; the adjusting and collecting periods were 14 and 7 days, respectively. Cows were fed ad libitum with total mixed ration (TMR). TMR was the mixture of silage and concentrate at the ratio of 39:61 (DM basis). The compositions of a basal diet (control) and two treatment diets were the same except for the difference of the sodium (Na) concentration. Dietary Na was varied by using Na₂CO₃. The concentrations of Na₂CO₃ in control diet and two treatment diets were 0%, 1% and 2% (DM basis), respectively. Dry matter intake and milk yield were significantly increased (P<0.05) by increasing the Na₂CO₃ concentration in diet. The percentages of milk composition: fat, protein, lactose and SNF were not significantly affected. No significant differences were observed in plasma concentrations of Na, K, and CI when Na₂CO₃ was added to diets. The ratio of urinary Na, CI: creatinene did not significant increase (P>0.05), but the urinary K: creatinine ratio was significantly increased (P<0.05) by addition of Na₂CO₃ to the diet. The concentration of fecal CI was unaffected whereas fecal Na of the control group was lower (P<0.05) than those of other groups given Na₂CO₃ supplementation. The concentration of fecal K in animals supplemented with 1 and 2% of Na₂CO₃ were lower in comparison to the control animals. The digestibility of DM, ADF, NDF, and CI were not different, but the digestibility for both Na and K was significant difference (P<0.05) when dietary Na₂CO₃ was increased. The pH and the concentrate of VFA in the ruminal fluid i.e. acetic acid (C₂), propionic acid (C₃), butyric acid (C₄), valeric acid (C₅) and acetic acid per propionic acid ratio (C₂:C₃) were not affected by addition of Na₂CO₃ in TMR diet.
