Weaning
Weaning is the process of gradually introducing an infant human or other mammal to what will be its adult diet while withdrawing the supply of its mother's milk. In the UK, weaning primarily refers to the introduction of solid foods at 6 months; in the US, it primarily refers to stopping breastfeeding.
The process takes place only in mammals, as only mammals produce milk. The infant is considered to be fully weaned once it is no longer fed by any breast milk.
Humans
In some cultures, weaning progresses with the introduction of feeding the child food that has been prechewed by the parent along with continued breastfeeding, a practice known as premastication. The practice was important throughout human history in that it naturally gave a child a greatly improved protein source in addition to preventing iron deficiency. However, premasticated food from caregivers of lower socioeconomic status in areas of endemic diseases can result in the passing of the disease to the child.How and when to wean a human infant is controversial. The American Academy of Pediatrics recommends feeding a baby only breast milk for the first six months of its life. Many mothers find breastfeeding challenging, especially in countries where many mothers have to return to work relatively soon after the birth of their child.
The American Academy of Pediatrics, the World Health Organization, the National Health Service Choices UK, and the National Health & Medical Research Council in Australia recommend waiting until six months to introduce baby food. However, many baby food companies market their "stage 1" foods to children between four and six months old with the precaution that the food is meant to be consumed in addition to breast milk or formula and is just for "practice". These practice foods are generally soft and runny. Examples include mashed fruit and vegetables. Certain foods are recommended to be avoided. The United Kingdom's NHS recommends withholding foods including those "that contain wheat, gluten, nuts, peanuts, peanut products, seeds, liver, eggs, fish, shellfish, cows' milk and soft or unpasteurised cheese" until a baby is six months old, as they may cause food allergies or make the baby ill. However, recommendations such as these have been called into question by research that suggests early exposure to potential allergens does not increase the likelihood of allergies, and in some cases reduces it.
Evidence from clinical trials shows that nutrition education of family members about infant weaning practices probably has a positive effect on babies' weight and height at 12 months compared with conventional management of weaning.
No matter what age baby food is introduced, it is generally a very messy affair, as young children do not have the coordination to eat neatly. Coordination for using utensils properly and eating with dexterity takes years to develop. Many babies begin using utensils between 10 and 14 months, but most will not be able to feed themselves sufficiently well until about two or three years of age.
Weaning conflict
At this point, the mother tries to force the infant to cease nursing, while the infant attempts to force the mother to continue. From an evolutionary perspective, weaning conflict may be considered the result of the cost of continued nursing to the mother, perhaps in terms of reduced ability to raise future offspring, exceeding the benefits to the mother in terms of increased survival of the current infant. This can come about because future offspring will be equally related to the mother as the current infant, but will share less than 100% of the current infant's genes. So, from the perspective of the mother's evolutionary fitness, it makes sense for her to cease nursing the current infant as soon as the cost to future offspring exceeds the benefit to the current infant. But, assuming the current infant shares 50% of the future offspring's genes, from the perspective of the infant's own evolutionary fitness, it makes sense for the infant to continue nursing until the cost to future offspring exceeds twice the benefit to itself. Weaning conflict has been studied for a variety of mammal species, including primates and canines.Age
There are significant individual and cultural variations in regards to weaning.Scientifically, one can ask various questions; some of the most straightforwardly empirical include:
- At what age do children self-wean?
- At what age do various societies normatively choose to wean?
- In comparison with other animals, especially similar primates, by various measures.
Considering biological measures of maturity, notably investigated by Katherine Ann Dettwyler, yields a range of ages from years to 7 years as the weaning age analogous to other primates – the "natural age of weaning". This depends on the measure, for example: weaning in non-human primates is often associated with eruption of permanent molars ; comparing duration of nursing to length of pregnancy yields a factor of about 6 in chimpanzees and gorillas ; body weight may be compared to birth weight ; and similarly for other measures.
Other studies are possible, as in psychological factors. For example, Barbara Rogoff has noted, citing a 1953 study by Whiting & Child, that the most distressing time to wean a child is at 13–18 months. After this peak, weaning becomes progressively easier and less distressing for the child, with "older children frequently wean themselves".
In her study of pre-war Japanese society The Chrysanthemum and the Sword, Ruth Benedict documents that Japanese children were usually not weaned until soon before a new sibling arrives.
However the government promoted eighth-month weaning which was reluctantly adopted by the middle-class in the benefit of the baby.
The factor that the Japanese meals did not include cow's milk or special vegetables for children also favored late weaning.
In other mammals
In science, mice are frequently used in laboratory experiments. When breeding laboratory mice in a controlled environment, the weaning is defined as the moment when the pups are transferred out of the mothers' cage. Weaning is recommended at three to four weeks after parturition.For pet carnivores such as dogs or cats, there are special puppy or kitten foods commercially available. Alternatively, if the pet owner feeds the parent animals home-made pet food, the young can be fed the same foods chopped into small pieces.
In cattle
Weaning in cattle can be done by many methods. Dairy calves in the United States are weaned off their mother at an average of around 7 weeks of age. Beef calves are not usually weaned off their dams until the calves are between 8 and 10 months of age. Before a calf is completely weaned off of milk, for both dairy and beef cattle, the calf must have developed a fully functioning rumen. For beef cattle, there are many methods of weaning that are used. Options include:- traditional weaning through total separation,
- two-step weaning with the use of a nose ring or other device, and
- fenceline weaning, which physically separates the calf from its dam by a fence.
Traditionally beef calves are weaned by abrupt separation, where the calves are separated from their dams and have no contact with each other, or by fence line weaning where the dam and calf have contact over a fence line. This has shown to cause high stress in both the dams and the calves. Both the dams and the young express high vocalization, reduced feed intake, reduced rumination, and an increased amount of time searching for each other as well as disrupting the social structure of the herd and of the calves. There is evidence that calves can undergo a form of depression post weaning, and have the potential to undergo illness that may need to be treated.
Two-step weaning is used to wean off beef calves from their dams over the space of a couple of weeks. With this method the calf is fitted with a nose flap that prevents suckling for a period of time, after which the calf is separated from the dam preventing contact. The nose flap does not limit the calf from performing any behaviors other than suckling; they are still able to drink and graze normally. Most research has shown that this method reduces the amount of stress that the calves endure. Studies show that prior to separation there is no change in feeding habits, social interaction to other members of the herd. Once the nose flap is removed and the calves are separated from the dams, there has been data showing less vocalization, less pacing and spent more time eating than calves that were weaned on a more traditional method.
Dairy calves are separated from their dam soon after they are born in most dairy operations. In some there is no contact between calf and cow for claimed health related reasons, such as preventing bovine paratuberculosis. However, one review found that changing the time of separation did not consistently improve overall cow or calf health. The main purpose of separating dairy cows from their calves to allow collection and selling of milk. The calves are then fed colostrum from the dam for the first few days, and then milk replacer. Dairy calves do not have ab libitum milk like beef calves. By limiting the amount of milk the calves receive it caused the calves to consume more feed which leads to faster development of the rumen. Dairy calves are usually weaned off milk early, usually at 4 to 8 weeks of age.