Serotonin and the Physiology of Calcium Homeostasis during the Transition Period

Adequate circulating Ca concentrations throughout the transition period are necessary for productive lactation, but large quantities of Ca are lost from maternal Ca pools into milk and colostrum. A rapid, large drop in maternal blood Ca causes 5-10% of cows to be afflicted with clinical hypocalcemia (CH) and an additional 50% to suffer from subclinical hypocalcemia (SCH). SCH and CH are significant risk factors of early lactation culling/premature removal from the herd (DeGaris and Lean, 2008; Reinhardt et al., 2011; Roberts et al., 2012). Furthermore, SCH increases risks of developing ketosis; displaced abomasum; and metritis; SCH depresses immune function; prolongs the interval until pregnancy is achieved; decreases pregnancy rate; and reduces overall productivity (DeGaris and Lean, 2008; Chapinal et al., 2011; Chapinal et al., 2012; Figure 1).