When it comes to reproduction, the feline species never ceases to amaze me. Despite our ever growing understanding of the hormonal mechanisms behind the reproductive function, things that are theoretically not possible might be seen from time to time in queens. It definitely reminds us that biology is drastically different from mathematics! Feline reproduction is still an open book, no doubt that more research is still needed to unravel all those mysteries.
Being in season… while nursing
And as a cat breeder, you might definitely run from time to time into some of those weird situations. For instance, some queens might give birth to a litter of kittens and a few days later, be back in season. Ok, this is not something exclusive to felines, we see it also in large animals. But nursing is (theoretically again) supposed to suppress the ovarian activity. Go figure!
This is definitely a troublesome situation when it happens, because the queen often loses interest for her kittens. For sure, that definitely means more work on your side. But I often also hear the following comment:
When this happens, new-born kittens get diarrhoea. Because the queen’s milk is altered.
Does being in season really alters milk composition?
True or false? So far, hard to tell. What I can tell you for sure is that, in the veterinary scientific literature, this is not documented.
When the queen is in season, her ovaries produce oestrogens. Those hormones do have an influence on the morphology of the mammary glands. However in cats, we don’t know if the composition of the milk that is being produced is really impacted.
This type of data exist in other species, like in humans and large animal. Those studies have shown, that at least in certain species, oestrogens will indeed modify the composition of the milk being produced by the female. Of course we cannot extrapolate to felines, but it is interesting to note that in those species, if variations in milk composition are noted, the parameters that might lead to development of diarrhoea in new-borns (like the lactose concentration) were not affected by the presence of oestrogens. Moreover, many of those studies mention that in this situation, milk composition still remains adequate to ensure proper growth in the corresponding new-born.
What should cat breeders do then?
So what does it mean for you cat breeders?
Basically, if a lactating queen starts her season, there is no reason - so far - to prevent the kittens from nursing.
If the kittens were unfortunately to develop diarrhoea, the way to approach it will depend... on their age, whether they are new-borns (less than 3 weeks of age) or going through weaning (typically 4-8 weeks).