Flushing is the practise of feeding breeding age goats,supplemental protein and or energy for 30 days prior to and 30 days following the introduction of bucks to achieve a weight gain during this period.This weight gain is usually accompanied by improved fertility,increased conception and twinning.Flushing may or may not be necessary for meat goat production depending on quantity and quality of available forage.If flushing is necessary,0.5lb of corn and/or 0.5lb of protein supplement day/head will usually suffice.
Meat Goat Production Handbook
By: Frank Pinkerton

if does are thin at breeding,kidding percent can be increased by flushing.Which is increasing nutrition during breeding.This puts the animal in  weight gaining condition and causes an increase in the ovulation rate.Flushing can be done by turning goats on fresh,lush pasture if it is available or by feeding grain.For flushing.corn is most often fed at the rate of 1/2 to 3/4 of a pound per head per day or 227 grams to 340.5 grams per head per day.Begin feeding 2-3 weeks before the bucks are turned in with the does and continue for 2-3 weeks after the introduction of the bucks,for a total feeding period of 4-6 weeks.Flushing generally results in a 10-20% increase in kid crop.Does in good condition generally will not benefit from flushing.