Final answer:
A client with mastitis should be advised to continue breastfeeding, starting with the affected breast to help clear the infection. The breast milk composition changes from colostrum rich in antibodies to mature milk, with milk fat content increasing during a single feeding.
Step-by-step explanation:
When educating a client with mastitis on how to feed the baby correctly, a nurse should advise the client to continue breastfeeding or expressing milk. It is important to feed the baby from the affected breast first, as emptying the breast regularly helps clear the infection. Besides, the baby's suction can help to remove the blockage causing the mastitis. Ice packs or cold compresses may be used to relieve pain and swelling between feedings, not before as cold can inhibit let-down.
The composition of breast milk is dynamic and changes significantly both during the first days of lactation and within individual feedings. Initially, the mother produces colostrum, which is rich in antibodies and acts as a form of active immunity for the newborn. Over the following days, the milk transitions to mature milk. During a feeding, the milk starts out as 'foremilk', which is more watery and satisfies the baby's thirst. As the feeding continues, the milk becomes richer in fat and is known as 'hindmilk', which helps to satisfy the baby's hunger.