عنوان مقاله [English]
نویسندگان [English]چکیده [English]
This study was conducted on 24 Holstein cows in close-up period, in a split-plot in time design, with a 2×2 factoriel arrangement and in a completely randomized framework to evaluate the effect of pre and postpartum dietary cation-anion differences (DCAD) on homeostasis of calcium, acid-base balance and the subsequent lactation performance. The first factor was prepartum DCAD for which the animals were randomly divided into two groups (12 cows each) one of them fed with a diet of -100 meq/kg of DM and the other fed with a diet of +100 meq/kg of DM. The second factor was postpartum DCAD. Following parturition the anionic group was divided into two groups of 6 cows, one group receiving a diet of +200 meq/kg DM DCAD and the other +400 meq/kg of DM DCAD. Same division was made for the cationic group. The experiment was continued till 63 d in milk. To reduce DCAD, anionic salt and to increase it sodium bicarbonate and potassium carbonate were added. Prepartum reduction of DCAD and postpartum increase of DCAD resulted in decrease in urine and blood pH and increase in urine and blood pH (P<0.01) respectively. Feeding diet of -100 meq/kg DM DCAD, caused significant increase in plasma calcium on d 1 and DM intake on the first week of lactation as compared with the cationic group. Postpartum increased DCAD to +400 meq/kg DM increased DM intake, fat corrected milk production, milk fat and total solid percentages. In conclusion, feeding negative DCAD in late gestation period is beneficial for dairy cows for better blood calcium homeostasis and improvement of health status and as well increase in postpartum DCAD that will positively affect productivity in a lactating period.