EFFECT OF PRE-PARTUM DIETARY CATION-ANION DIFFERENCE LEVEL ON PHYSIOLOGICAL PERFORMANCE OF DAIRY COW

Ths investigation aimed to study the effect of dietary cation: anion difference (DCAD) on some physiological parameters in dairy cow, including blood serum and urine concentration of mineral elements, acid-base balance, calcium homeostasis, and health status. This experiment began before the expected due date (21 days) and continued until calving and insemination for the next pregnancy. Twenty multiparous cows in second and third parity were targeted as experimental animals. Animals were divided according to the parity to four groups, five cows each. Animals were housed in four separate open areas provided with water sinks and shades. All animals were fed on a basal diet without (G1) or with different DCAD, including +90,0, -90 and -150 mEq/kg of DM, in G1, G2, G3, and G4, respectively, During the postpartum period, cows in all groups were fed on diet with DCAD of + 200 mEq/kg DM) anionic salt. Results indicated that serum calcium concentration increased significantly (p<0.05) with decreasing DCAD. With positive DCAD (+90 mEq/kg DM), serum calcium concentration was 6.5968 mg/dl, increased significantly to 7.2095 mg/dl with zero DCAD. When DCAD decreased to -90 or -150 /mEq/kg DM), serum calcium concentration increased to 7.7263 and 7.9486 mg/dl with anionic salts, respectively with no significant differences. The urinary calcium concentration had the same trend of blood calcium concentration. Total Serum phosphorus concentration decreased significantly (p < 0.05) with decreasing DCAD, the highest serum phosphorus concentration was recorded for G1 (5.11 mg/dl), and the lowest was obtained with G4 (4.67 mg/dl). The urinary pH decreased from 2.009 for G1 to 1.808 for G4. Moreover, DCAD level affects significantly urinary magnesium, urea and creatinine, while serum magnesium, total protein, albumin, globulin, AST and ALT weren’t affected significantly by treatment. Data indicated that there was a significant interaction between treatment and time before and after parturition effects on Beta hydroxyl Butyric Acid (BHBA) concentration. The data also showed that the thyroid hormone (T4) was unaffected by the therapy, and as expected, progesterone levels dropped sharply during delivery and kept dropping until 14 days postpartum.It could be concluded that the dairy cattle breeders adjust DCAD at transition period to -150 /mEq/kg DM pre-partum and to +200 /mEq/kg DM post-partum.