SOUTHERN JOURNAL OF AGRICULTURAL ECONOMICS
JULY, 1977
A DRY MATTER QUALITY APPROACH TO
PLANNING FORAGE-BEEF SYSTEMS*
Kim B. Anderson and Odell L. Walker
Forage quality and quantity vary by species, time
of year, level and time of fertilizer application and
grazing system [6].1 Livestock nutritional require-
ments change with age, rate of gain, weight, date of
calving and percentage calf crop [7]. Pasture forage
production and livestock forage requirements depict-
ing both quality and quantity need to be compiled by
calendar periods to determine optimal pasture pro-
grams and livestock systems.
Animal unit months (AUM) and total digestible
nutrients (TDN) are the predominant measures of
forage quantity produced and required.2 Neither
measurement adequately reflects quality and quantity
in forage production and beef requirements through-
out the production cycles. Therefore, optimal forage-
beef systems obtained from planning models using
AUM or TDN may in fact be infeasible or non-
optimal. This paper explains development and use of
a dry matter (DM) quality measurement concept for
formulating forage-beef management programs in a
linear programming (LP) framework [1].
Forage-beef systems obtained using the DM
quality concept in an LP model showed a distinct
complementarity between cow-calf and stocker steers
based on their different forage requirements. A
diversified organization of warm and cool season
pastures and spring cow-calf, fall cow-calf and
October to June stockers was obtained. The forage
mix meets livestock quality and quantity require-
ments throughout the year. Results from models
using AUM or TDN did not show these relationships
[4,5].
The authors benefited from work completed by
cooperators in Southern Regional Project S-67, “Eval-
uation of the Beef Production Industry in the
South.” Most LP models in that study used net
energy, digestible energy, metabolizable energy or
total digestible nutrients, dry matter and digestible
protein as measures of nutrient production and
requirement. DM was used as a maximum constraint
relating to stomach capacity and intake. When the
forage is broken into two month or smaller calendar
periods and allocated by animal class, a massive LP
matrix results from the S-67 model.
The study presented here sought to simplify the
model while retaining many desirable developments
produced in S-67. One goal was to derive a tool suited
to applications at the farmer level through coopera-
tion of pasture, livestock and economic specialists.
User understanding and acceptance are important.
The model must be of manageable size and com-
plexity. Most importantly, needed data must be
readily accessible.
THE DM QUALITY APPROACH
Estimates are available for DM production by
forages and requirements by livestock. Pounds of DM
by quality, measured by megacalories (Meal) of
metabolizable energy per kilogram of DM (ME/kg)
and calendar periods, were used to measure forage
production and livestock nutritional needs. This
concept of dry matter quality ties quality and
quantity of forage together.
Kim Anderson is Extension Associate, Farm Management (formerly Graduate Research Assistant) and Odell L. Walker is
Professor, Department of Agricultural Economics, Oklahoma State University.
*The authors acknowledge the valuable contributions of colleagues at O.S.U., the Nobel Foundation, Ardmore, Oklahoma
and the S-67 Regional Research Committee.
ɪ In this paper, the term ‘forage’ is used to include pasture and harvested feedstuff, excluding grains and concentrates.
2An animal unit month is defined as the amount of feedstuff required for an animal unit for one month. An animal unit is
defined as AU = W∙75 ∕1OOO∙75. However, many farm management specialists have used AU = W∕1000.
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