Agriculture Reference
In-Depth Information
enforced. The model incorporates the effects of
policies on feed selection, profitability and
environmental impacts for a hypothetical dairy
cattle herd. Model results are discussed, and the
marginal costs of methane emissions mitiga-
tion strategies are generated through a linear
programming framework.
applied to growing pigs, and from observations
that nutrient requirements vary greatly between
pigs with similar characteristics, different meth-
ods of estimating nutrient requirements were
discussed. In a population of animals, between-
animal variability plays a role in determining the
proportion of animals that have nutrient require-
ments met with a diet formulated for the average
animal. Under the assumption that nutrient
requirements in a population of animals follow a
normal distribution, half of the animals are being
underfed and half of the animals are being fed
excessive nutrients. The reasoning is that, in a
normal distribution, the mean coincides with the
median, which represents the 50th distribution
percentile. By using the cumulative distribution
of a specific nutrient requirement, we could
determine the proportion of animals that are
meeting their nutrient requirements under differ-
ent feeding strategies, and investigate the rela-
tionship between nutrient excretion and diet
formulation. As a result, the trade-off between
increasing the proportion of animals that have
their nutrient requirements met and increased
nutrient excretion can be examined. For a com-
prehensive discussion of the mechanisms by
which precise feeding strategies can increase the
efficiency of nutrient utilization, refer to Pomar
et al
. (2009), where an application of this concept
is described in the feeding of growing pigs.
A better understanding of feed nutrient
composition and availability for animal produc-
tion can be achieved by the division of feeds
according to nutrient digestibility. Feeding sys-
tems in which protein fractions are divided
according to digestibility (Sniffen
et al
., 1992;
NRC, 2001) enable, for instance, a more precise
determination of protein supply. Accordingly,
the division of feeds based on digestibility and
availability leads to a more specific and precise
diet formulation. Therefore, diets can be formu-
lated to deliver nutrients at the calculated ani-
mal requirement level. On the other hand, the
division of feeds according to nutrient digestible
fractions is usually dependent on the animal
production level and dry matter intake.
Consequently, knowledge of animal intake is
necessary for the determination of feed nutrient
availability and animal intake should be deter-
mined before the diet is formulated. From a diet
formulation point of view, especially from a lin-
ear programming perspective, fixing the intake
Feed Management
Feed management is a general term, and can
include several areas in a production unit.
Purchasing of feeds, feeding strategies, feed stor-
age, mixing and formulation of diets are key ele-
ments in feed management. Information related
to animal production also plays a key role in feed
management, for example, animal characteris-
tics that affect animal nutrient requirements. In
this chapter, we discuss two feed management
topics that can be applied to the minimization of
the environmental impacts of livestock. The first
topic is related to the incorporation of between
animal variability into diet formulation and the
use of this information in reducing nutrient
excess feeding. The precise feeding concept is
introduced, with an example of different feeding
phases throughout the feeding period of pigs.
The second topic discussed is related to practical
aspects of diet optimization, e.g. the conversion
of a system such as the NRC (2001), in which
energy and protein availabilities are intake
dependent, into a linear programming frame-
work. The division of feeds based on digestible
fractions, for different levels of intake and
production, can increase precision in the cal-
culation of feed nutrient availability and, theo-
retically, reduce the environmental impacts of
livestock production.
The precision feeding concept can be incor-
porated in a production unit through different
strategies. For example, increasing the number of
feeding phases in a production system reduces the
variability of animals within a pen. In the case
of growing animals, weighing the animals fre-
quently can increase the precision in calculating
nutrient requirements. In essence, a better under-
standing of feed nutrient availability and a more
precise determination of animal nutrient require-
ments are key elements in feeding diets that
deliver nutrients at the requirement level. Pomar
et al
. (2009) examined precision feeding techniques
