An Experimental Study of Weaning in the Domestic Cat

Abstract

The first part of the paper describes the process of weaning in domestic cats. The subjects were seven families of cats living under laboratory conditions-each family consisting of a mother and her two kittens, living in their own large indoor pen. Observations were carried out at regular intervals from the third week after birth until the kittens were 10 weeks old. Weaning is viewed as the period during which the rate of milk transfer from mother to offspring drops most sharply. According to this definition, weaning commenced when the kittens were four weeks old and was largely completed by the time they were seven weeks old. During the weaning period mothers made suckling progressively more difficult for their kittens by increasingly adopting body postures that blocked access to their nipples. The amount of suckling declined sharply from four weeks after birth and seldom occurred after seven weeks. Kittens were first seen to eat solid food during the fifth week, and this was associated with a large increase in the variability of their daily weight gain. Prior to the start of weaning, mothers' food intake was approximately double that of non-lactating females. Male kittens grew more rapidly than their sisters and were significantly heavier. However, there was no evidence that males suckled more than females prior to the start of weaning. In general, weaning was characterised by a gradual reduction in the ease with which kittens could suckle, rather than by any overt rejection or aggression by the mother. The absence of any obvious weaning conflict is thought to be related to the favourable housing conditions (small litter size, ad libitum food, freedom from disturbances, etc.) used in this study. The second half of the paper describes the results of an experiment in which maternal lactation was interrupted during the first week of weaning. Seven Experimental (E) mothers were injected with the lactation-blocking drug bromocriptine on days 28, 30 and 33 post partum, each injection being sufficient to interrupt lactation for about 18-24 h. In the period immediately following the injections (days 29-46), E mothers and their kittens were more active than the controls, and E mothers washed their kittens more. Later on (days 47-70), E kittens suckled more than the controls-notably in the eighth week after birth, at a time when suckling would normally be rare. E mothers appeared to be more willing to let their kittens suckle during this period, as they adopted a fully accessible posture more often, and a blocking posture less often, than controls. The overall pattern of results is interpreted in terms of an initial withdrawal from the kittens in the period immediately after lactation was interrupted, followed by a later resumption of maternal care and a postponement of the end of weaning. Perhaps as a result of this continuation of suckling, the experimental treatment had no overall effect on the kittens' growth, although the Experimental kittens did grow more slowly in the week of the injections. One tentative hypothesis is that the apparent postponement of weaning represents a compensatory response to the earlier reduction in the rate of parental investment. The first part of the paper describes the process of weaning in domestic cats. The subjects were seven families of cats living under laboratory conditions-each family consisting of a mother and her two kittens, living in their own large indoor pen. Observations were carried out at regular intervals from the third week after birth until the kittens were 10 weeks old. Weaning is viewed as the period during which the rate of milk transfer from mother to offspring drops most sharply. According to this definition, weaning commenced when the kittens were four weeks old and was largely completed by the time they were seven weeks old. During the weaning period mothers made suckling progressively more difficult for their kittens by increasingly adopting body postures that blocked access to their nipples. The amount of suckling declined sharply from four weeks after birth and seldom occurred after seven weeks. Kittens were first seen to eat solid food during the fifth week, and this was associated with a large increase in the variability of their daily weight gain. Prior to the start of weaning, mothers' food intake was approximately double that of non-lactating females. Male kittens grew more rapidly than their sisters and were significantly heavier. However, there was no evidence that males suckled more than females prior to the start of weaning. In general, weaning was characterised by a gradual reduction in the ease with which kittens could suckle, rather than by any overt rejection or aggression by the mother. The absence of any obvious weaning conflict is thought to be related to the favourable housing conditions (small litter size, ad libitum food, freedom from disturbances, etc.) used in this study. The second half of the paper describes the results of an experiment in which maternal lactation was interrupted during the first week of weaning. Seven Experimental (E) mothers were injected with the lactation-blocking drug bromocriptine on days 28, 30 and 33 post partum, each injection being sufficient to interrupt lactation for about 18-24 h. In the period immediately following the injections (days 29-46), E mothers and their kittens were more active than the controls, and E mothers washed their kittens more. Later on (days 47-70), E kittens suckled more than the controls-notably in the eighth week after birth, at a time when suckling would normally be rare. E mothers appeared to be more willing to let their kittens suckle during this period, as they adopted a fully accessible posture more often, and a blocking posture less often, than controls. The overall pattern of results is interpreted in terms of an initial withdrawal from the kittens in the period immediately after lactation was interrupted, followed by a later resumption of...