The end of dioestrus (the period corresponding to pregnancy or false pregnancy) is indicated hormonally by de decrease in the level of progesterone in the blood, a temporary increase in oestrogen that allows dilatation of the cervix, and an increase in prolactin, the hormone responsible for colostrums and milk production.;
These hormone changes are the same whether the bitch is pregnant or not, which explains the frequency of “false-pregnancy lactation.” This phenomenon is also observed in packs of wild dogs, mainly in bitches of lower rank in the hierarchy, who can then serve as nursemaids if a dominant bitch’s milk supply should fail. It emphasizes the importance of the mind in triggering lactation, which is true of many mammals.
Given this “mental” factor, it is understandable that a bitch who is not comfortable with motherhood, whose choice of nest has been overruled, or who has been anesthetized for a Caesarean can show a clear delay in milk production. This condition can be treated by a change in environment, by homeopathic herbs or by administering certain antiemetics that stimulate secretion of prolactin by the central nervous system.
Once of the first puppies have been born, milk secretion continues on its own by a neurohormonal reflex action. Nursing or massaging of the teats stimulates the secretion of an other hormone, oxytocin, which causes the milk to move into the milk ducts. This mechanism is proportional to the number of nursing puppies, and so allows milk production to adapt to the puppies’ appetites, which in a sense take priority over the mother’s health.
The Milk production
The first milk, called colostrums, is secreted by the mother for two days after whelping. It has neither the appearance, nor the composition of regular milk. In fact, it is yellowish and translucent that it can easily confused with pus.
Colostrum is much higher in proteins than milk. In addition to its nutritive value, it stimulates the first defecations by the puppies and provides 95% of the antibodies needed to protect them against infection. In this way, the mother passively transfers her immunologic memory to the puppies for a period of 5 to 7 weeks, until they are able to actively defend themselves against infections.
Puppies are able to absorb these maternal defences only during a period of less than 48 hours after birth. After this time, the antibodies are destroyed in the stomach before they can be absorbed, and so lose their effectiveness. In this case, the puppies are protected only by the antibodies that were able cross the placental barrier during gestation (not more than5%)
Colostrum is replaced by milk in a few days. The composition of the milk depends on the size of the breed (German shepherds produce milk which is rich in proteins), in individual genetics and which teat is producing it (the posterior teats are more productive)
On average, lactation last six weeks after whelping, with maximum production at about the third week. In the following weeks, decreasing milk production causes the mother to regurgitate her food to supplement the puppies’ milk diet. The puppies also begin to take an interest in her dish. This period marks the beginning of gradual weaning, which ends at about six weeks when the puppies begin eating growth-formula dog food.
The amount of milk a bitch produces can be evaluated by regularly weighing the puppies before and after they nurse. Such measures allow us to determine a curve of milk production as a function of factors that influence it directly (weight and size of the mother, number of nursing puppies) and to formulate a predictive curve for estimating milk production:
Thus it can be calculated that a German shepherd bitch weighing 32kg and nursing 8 puppies will produce 2.4 times her own weight to wean her litter.
Of course ,it is very presumptuous to try to “pin down” milk production using an equation that also ought to take into account parameters such as the temperature during the maternity period, the mother’s water consumption, parity and stress level,
to name a few:
Nevertheless, this equation allows us to obtain a relatively close estimate of the amount of milk produced when lactation peaks, namely, 4% of the total amount produced. This means that the bitch produces about three liters of milk per day at the height of lactation, which obviously requires a considerable nutritional adjustment to avoid excessive weight loss during this period, which can be considered as the most difficult and demanding period of her sexual cycle.