Friday, March 12, 2010

How fast does a puppy grow…

Years ago when Mischka was a puppy I decided to measure her growth rate (along with how much food she ate and lots of other information). I remember trying to find information, charts or tables that would give me an idea of what was normal - but I was unsuccessful at the time. The method I used was simple and crude - weighing myself alone and while holding the pup on a bathroom scale and recording the difference. The scale did repeatedly give the same result for repeated measurements but only had a +/- 0.5 lb precision. While most of the time measurements were taken after the puppy voided, there was still some noise due to an occasional "non-empty" pup.

So lets look at the data - I limited the time period to the first year for simplicity. On the first graph we can see the total weight increase at a nearly linear rate until around 160 days, then increase at a slower rate for another 2 months before it levels off.

In the second graph we can see the nature of the rate of change a bit cleaner. Here, by using a log scale on the vertical axis it becomes apparent that the rate of change in weight is adjusted over time and not just a fast and slow rate that the previous graph suggested. In the beginning the slope is very steep and as the days pass it gradually decreases forming a beautiful curve.

On the next graph we can see that over time the percentage of of the change in weight relative to the total weight conveys the same information in a slightly different manner. Here, the transition from increasing growth rate (the acceleration of growth) to a decreasing growth rate occurs around 160 days. The two things that stand out here are the increased noise in the measurements early when the puppy weight was low and also that the transition to a stable weight (a growth rate of 0) is stretched out gradually over a long time.

In the last graph we can see that the actual amount of weight change per day is highly variable. A measurement on any particular day may or not represent the days just before or after. One the other graphs this isn't as clear. It is interesting that when the growth rate is decreasing (after day 240) on some days there is an increase in weight and on other's there is a decrease. I would have expected a simple decrease in the weight gained per day but that's not what happened. Biology always has surprises.

These are all just the results of a simple set of measurements I made and may or may not represent what one wold see in other dogs. I do suspect the general rates of change would be similar but the intervals and absolute weights may be different. I am only making this available because years ago I would have liked to have seen something like this, but I could not find this type of information.