The method which I use is to offer an appropriate prey item every 5-15days (or so) dependet on both the species and age of the snake. Now I hear you ask how do you figure out what is classed as an appropriately sized prey item? Worry not help is at hand. I personally believe that an appropriate prey item is at minimum as thick as the snake at its widest part. This doesn't mean that you should measure exactly, it is just a rough guide (a guesstimate if you will). Now we have a minimum, it is important to avoid excessively large prey items as this can lead to problems such as regurgitation. As a general rule of thumb I will offer a prey item around 1.5 times the thickest part of the snake (species dependent). Once again this rule isn't hard and fast, meaning that there is room for slight deviation as variety is the spice of life. I occasionally will mix up the prey size for a couple of feeds or so, just to keep them on their toes. To be frankly honest I have never had a problem with any of my snakes feeding when using this method of prey size selection, and my thinking is why fix it if it isn't broken.
As well as selecting a good size prey item it is important to highlight the frequency of feeding in order to promote healthy growth and avoid excessive weight gain. For my hatchling snakes of any species I will offer a prey item every 5-7 days. I stick to this frequency for my hognose thoughout adulthood, however maintain prey size closer to the minimum size as I find this to work well for the species. As the snake increases in size and age I will offer a larger food item less often, eventually offering a meal every 7-10 days (give or take) for my corn snakes and my royal pythons, and every 10-15 days (give or take) for my boas when they are adults. I find that by providing this method of feeding it prevents excessive over feeding , which in turn helps to avoid health issues related to an overweight snake such as fatty deposits around organs. It is also important to note that regular excercise will aid in conversion of the food in to well toned body mass instead of fat. Let's face it nobody likes a fat snake.
Well that's it really. I know it is short and sweet, however I feel that trying to work out the percentage relation between the snake and prey item is too much hassle and does not result in any benifit for the snake. Now I have slightly more time available I will be updating this blog more often, so stay tuned for more updates.