Influence Of Dietary Cation-anion Difference On Milk, Blood And Urine In Lactating Cows

Three experiments were conducted to research and develop the influence of dietary cation-anion difference on milk, blood and urine in lactating cowsExperiment 1. Effects of dietary cation-anion difference(DCAD) with a positive value of +30, +40 and +50 mEq/100g dry matter(DM) respectively on milk production level, serum and urine mineral contents of early lactating dairy cows was examined in a randomized complete design. Three DCAD diets were randomly allotted to three groups. Each group contained three Holstein dairy cows. A linear increase in DMI and urine pH was recorded with increasing DCAD value positively (P<0.05). Urine sodium and potassium excretion increased and the urine calcium and creatinine excretion decreased by a relatively higher DCAD value; the concentrations of other irons were unaffected. Serum calcium concentration decreased and phosphorus concentration increased significantly with increasing DCAD values positively (P<0.05). For DCAD of +40 mEq/100g DM, milk yield and 4%FCM was 29.47±0.54kg/d , 28.42±0.50kg/d, respectively. Milk protein and fat percentage was 5.95% and 2.88% higher on DCAD of +50mEq/100g of DM than +30mEq/100g of DM.Experiment 2. Effects of dietary cation-anion difference(DCAD) with a positive value of +25, +35 and +45 mEq/100g dry matter(DM) respectively on milk production level, serum and urine mineral contents of mid-lactating dairy cows was examined in a randomized complete design. Three DCAD diets were randomly allotted to three groups. Each group contained three Holstein dairy cows. A linear increase in DMI and urine pH was recorded with increasing DCAD value positively (P<0.05). Urine sodium and potassium excretion increased and the urine calcium and creatinine excretion decreased by a relatively higher DCAD value; the concentrations of other irons were unaffected. Serum phosphorus concentration increased significantly with increasing DCAD values positively (P<0.05). For DCAD of +35 mEq/100g DM, milk yield and 4%FCM was 29.12±0.65kg/d , 28.73±0.96kg/d, respectively. The yield of milk protein and lactose was 12.05% and 5.97% higher on DCAD of +35mEq/100g of DM than +45mEq/100g of DM.Experiment 3. Effects of dietary cation-anion difference(DCAD) with a positive value of +15, +20 and +25 mEq/100g dry matter(DM) respectively on milk production level, serum and urine mineral contents of late lactating dairy cows was examined in a randomized complete design. Three DCAD diets were randomly allotted to three groups. Each group contained three Holstein dairy cows. A linear increase in urine pH was recorded with increasing DCAD value positively (P<0.05).Urine potassium increased by a relatively higher DCAD value, the concentrations of other irons were unaffected. The yield of 4%FCM increased with increasing DCAD values positively (P<0.05).The others were unaffected.