  BeefTalk:
How Many Cows do You Have?
By Kris Ringwall, Extension Beef Specialist,
NDSU Extension Service
When do casual acquaintances in the cattle business become friends? That’s
easy: when they share how many cows are in their operations. It is considered
poor etiquette to ask a fellow producer how many cows his or her operation runs.
Just like cash in the checking account, discussing cow numbers is always done in
a round-about way. Cow numbers and cash are confidential figures.
The business of beef production, however, requires an inventory number to
accurately provide answers for management. Since most numerical calculations
within a cow herd are generally presented based on a value per cow, recommended
procedures need to be followed to properly document herd size. How many cows do
you really have?
Throughout the course of the year, the cow herd varies. The maximum number of
cows within a herd occurs before bull exposure and remains relatively constant
until weaning. The minimum number of cows is at calving, generally associated
with a dramatic downward trend in cow numbers following weaning and a general
leveling off of numbers just prior to calving. So what is the real number of
cows?
The statistically correct inventory number would be the average monthly
number of cows maintained throughout the year, commonly called the perpetual
inventory. Reporting the number exposed would bias the number upward, and
reporting the number calving would under estimate the true number of cows.
Considerable variation exists within individual herd deviations from the
number of cows calving or the exposed versus the actual mean monthly (perpetual)
cow inventory. Herd size stability and time of cow culling impact the deviation
considerably.
After all, a producer can cull in the fall, spring or some combination and
also be increasing, decreasing or stabilizing the inventory. The Cow Herd
Appraisal Performance Software (CHAPS) does provide a perpetual inventory. Let
me use three CHAPS herds to illustrate the point.
CHAPS herd A has 291 cows calving and exposes 342 cows to the bull. The
perpetual inventory is 319 cows. This herd is decreasing inventory and culls in
the fall. Following weaning, the 342 cows exposed overestimates cow numbers by
over 7.2 percent and the 291 cows calving underestimates cow numbers by 8.8
percent.
CHAPS herd B is increasing cow numbers and culls similar numbers of cows in
the spring and fall. This herd calves 322 cows and exposes 353 cows to the bull.
The perpetual inventory is 339. In this example, the 353 cows exposed to the
bull overestimates cow numbers by 4.1 percent and 322 cows calving
underestimates cow numbers by 5 percent.
CHAPS herd C calves 320 cows, exposes 324 cows and has a perpetual inventory
of 319 cows. This herd is decreasing cow numbers and culls in the spring. Under
this scenario, cows exposed only overestimates cow numbers less than 1 percent
and cows calving underestimates cow numbers by 0.5 percent. Additional
combinations of herd stability and time of culling will only indicate the
difficulty in counting cows.
So how many cows do you really have? Obviously there is no simple answer.
However, for a point of standard conversation, if someone asks you how many cows
you have, to be technically correct, the number is the perpetual cow inventory.
Ranch productively, if expressed per cow, needs to be the perpetual cow
inventory value expressed as a 12-month average. Good luck counting cows. May
you find all your ear tags.
Your comments are always welcome at www.BeefTalk.com.
For more information, contact the North Dakota Beef Cattle Improvement
Association, 1133 State Avenue, Dickinson, ND 58601 or go to www.CHAPS2000.COM
on the Internet. In correspondence about this column, refer to BT0085.
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Source: Kris Ringwall, (701) 483-2427, kringwal@ndsuext.nodak.edu
Editor: Tom Jirik, (701) 231-9629, tjirik@ndsuext.nodak.edu
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Graphic:
Inventory for Three CHAPS Herds
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Herd A Herd B Herd C
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Number of cows calving 291 322 320
Number of cows exposed to the bull 342 353 324
Perpetual Inventory 319 339 319
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