Agriculture Reference
In-Depth Information
system concept is an example of a multiple input/multiple output control system,
with parameters such as animal performance (measured by body weight gain, milk
production, egg production, etc.) or environmental impact (gaseous or particulate
emission rate) as data for feedback control. Initial efforts in development of an
integrated management system stem from economic optimization models that use
robust animal growth and feed conversion models that are sensitive to environment
conditions, along with input costs such as feed, electrical costs, and fuel, and opti-
mize environment selection and control for maximum profit (Timmons and Gates,
1986; Gates and Timmons, 1986, 1987, 1989; Gates et al., 1994; Christianson and
Fehr, 1983).
8.7.1 N
UTRITION
AND
G
ROWTH
C
ONTROL
Feed costs represent the single greatest expense in animal production. Improving
efficiency of nutrient utilization is paramount as traditional feedstuffs such as corn
and soy are diverted to other markets such as biofuels production. In typical com-
mercial practice, swine and poultry are fed in phases according to age or weight,
with rations formulated on a least-cost basis.
Nutrition control aims to optimize production efficiency through continual
adjustment of diet composition over the production cycle according to the needs of
the animal to avoid overfeeding of nutrients. Systems currently marketed for nutri-
tion control in swine operations blend the phase diets over time, gradually intro-
ducing the subsequent phase diet to match predicted nutrient needs (Frobose, 2010;
Sulabo et al., 2010). A prototype commercial system for feed blending as part of an
“integrated management system” for broiler production was described by Frost et al.
(2003), but to date has seen limited application.
Growth control is of particular interest for meat poultry production that targets
specific market weights and uniformity goals and seek to avoid health problems
resulting from rapid growth rates of modern genotypes. Control of growth trajec-
tory in broilers has been successfully implemented via model-based control of feed
supply (Aerts et al., 2003) and in broilers and swine through manipulation of diet
composition (Stacey et al., 2004; Parsons et al., 2005). Implementing model-based
control of nutrition is complicated from limitations of current predictive models to
account for deviations resulting from typical management challenges such as disease
(Frost et al., 2003). However, nutrition and growth control may also be applied as
tools to limit emissions by reducing overfeeding of nitrogen (Robertson et al., 2002).
8.7.2 I
NTEGRATION
OF
A
NIMAL
R
ESPONSE
Integrating animal response into control decisions would allow for enhanced man-
agement of the housing environment to mitigate adverse impacts on performance
or well-being (Wathes et al., 2001). As noted by Hamrita and Mitchell (1999),
much of the difficulty in applying control theory to animal production systems is
definition of the plant. Full specification of the plant would include both the build-
ing responses, the resulting microenvironment, and animal responses. Inadequate
description of animal response to environments and stressors provides a challenge in
