The Inf luence of Subclinical Hypocalcemia on Production and Reproduction Parameters in Israeli Dairy Herds

Gild, C. 16 INTRODUCTION Parturient paresis is a metabolic disorder occurring close to parturition especially in high producing dairy cows. The disease is characterized by a rapid decline in blood calcium (Ca) concentrations. Nearly all mature cows experience some degree of hypocalcemia during the first day after calving as the intestine and bone adapt to the Ca demands of lactation (1). In some cows, the mammary drain of Ca causes extracelluar and blood Ca concentrations to decline to levels that disrupt neuromuscular function, resulting in the clinical syndrome of “Milk Fever”. This Ca decline lasts in some cases for several days postpartum (2). Post-parturient hypocalcemia is divided into clinical and subclincal forms (3, 4). The literature indicates that the clinical form is associated with an increase in post-parturient diseases (5, 6, 7, 8). In large parts of the United States and some European countries it is assumed that the subclinical form is also related to post parturient diseases (5, 9, 10, 11) and has a negative impact on profitability. Therefore, many dairies use expensive feed additives to reduce the incidence of this form (12, 13). Fatty acid metabolism might differ between cows with subclinical hypoclacemia and their normocalcemic counterparts (14) however, there is conflicting evidence regarding the impact of subclinical blood calcium levels on milk production, reproduction parameters and post-parturient disorders (10, 14, 15). Most of the research The Inf luence of Subclinical Hypocalcemia on Production and Reproduction Parameters in Israeli Dairy Herds