Document Type : Research Paper
Former M.Sc. Student, Department of Animal Science, Arak University, Iran
Associate Professor, Department of Animal Science, Arak University, Iran
Assistant Professor, Department of Animal Science, Arak University, Iran
Supplementing anionic salts to make negative DCAD in close-up heifers’ diets is still a challenging topic in formulation of dairy cattle rations. Twelve close-up Holstein heifers (21 ± 7 d expected to calving date) were fed individually and allocated to two treatments of 6 animals each. Experimental treatments were; 1) positive DCAD with level of +165 meq/kg basis on dry matter; and 2) negative DCAD with the level of -85 meq/kg basis on dry matter. Dry matter intake (DMI), milk yield and composition, colostrum yield and its immunoglobulins content and some blood metabolites (pre- and post-partum) were evaluated. The results show that DMI was similar between treatments. The blood pH was lesser in negative-DCAD fed heifers. Among blood metabolites, only Ca was increased in negative-DCAD fed heifers. Colostrum and milk yield and milk composition, colostrum concentrations of IgM and IgA were similar between treatments. However, serum and colostrum concentrations of IgG were slightly increased in negative-DCAD fed heifers; a further research should be carried out to elaborate on the effects of using negative-DCAD rations in close-up heifers exposed to stressful conditions.