Script with sleeping between tasks

sleeping=1
if [ "$1" != "" ]; then
    sleeping=$1
fi

echo "     (___)"
echo "     (o o)____/"
echo "      @@      \\"
echo "      \ ____, /"
echo "      //    //"
echo "     ^^    ^^"

echo "Cowd started."
echo "Mooing every $sleeping seconds."

start=$(date +%s)
while true
do 
    now=$(date +%s)
    echo "$(($now-$start)) Moo!"
    sleep $sleeping
done