Lynn said:
we are getting ready to butcher and want some idea of how much our hamburger on the hoof weighs..
I found this 'formula' on another post, but want to be sure it is correct...
heart girth X heart girth X length :/: 300
:/: means divided by..
why would you use the heart girth measurement twice?
i'm just looking for an estimate, obviously...
Thanks,
Lynn
(He's much too big to hold and stand on the scales with like I do the goats!!! LOL)
You don't use the heart girth twice--you square it-- (multiply it x itself)--not the same as "using it twice".
The forumula is amazingly accurate, and has been around a long long time. It works on most livestock and even for dogs, but the places you measure at varies, and of course that "300" constant is really a plugin that changes with species and even a different one for calf/yearling/ and mature cattle. Please note you measure hearthgirt a little differently for dairy than you would a beef animal.
I am NOT a math guy, but I have a little understanding of area and volume and I also asked elsewhere one time and had it explained by some pretty sharp math folks.
Squaring the heartgirth (C) gives you approx area. You will also need to compute the volume of the animal's torso, and that comes by multiplying the C squared by the length measurment.
(The real equation used to figure the circumference of a shaped object of course is C= pi * r2 )
The livestock formula uses circumference, which you can measure rather easily, instead of radius or diameter, which would usually be impractical to measure on a live animal. The circumference is squared because you are using it to estimate cross section area; multiplying by the length will then yield a volume.
Weight estimate = volume * density = area * length * density
Or:
The usual equation for the area of a circle (or of the circular cross section of a cow) is:
A = pi * R2 ... where R = radius, pi = 3.141592...
Since the circumference C = 2 * pi * R ... then
R = C / (2 * pi)
Dividing by the plugin or 'constants' (300 in this case) neatly takes care of errors caused by the fact that a cow is an irregular shaped object. It's just an empirical value. Different plugins for different age groups and different scales (kg-lbs, even troy ounces)
There are also websites, that have taken some of the work out for you--a set of tables in which all you need is the initial measurements. Some are breed specific, and rerquire only a heartgirth measurement.
(hope it helps--took me a while to digest it all too--been over 45 years since I sat in a classroom)
