Alternative Production Systems: Influence on Pig Growth Pork Quality
Jessica G. Gentry, Mark F. Miller and John J. McGlone
Pork Industry Institute
Texas Tech University
Lubbock, TX 79409-2141
USA
http://www.pii.ttu.edu
Correspondence:
john.mcglone@ttu.edu
Summary
Consumer preferences for pork from conventional and
alternative production systems were assessed in the USA and Europe. A majority of consumers say they are willing
to pay more for products that are produced as “sustainable”, “natural” or with
other assurances without mentioning any improvements in pork eating
quality. We were surprised at first to
see that consumers now put a value on some social features of the production
system quite apart from the pork’s appearance or sensory qualities. A niche market is available for pork
produced with certain socially-acceptable assurances even if no real difference
in pork sensory qualities can be consistently demonstrated through objective
research. A comparison of research on
the effects of housing systems on pig growth characteristics and meat quality
has been compiled in this report.
Controlled and field studies were conducted at Texas Tech
University. Our results and those in
the scientific literature do not entirely agree, perhaps due to geographical
location, climate and genotypes evaluated.
When we controlled both birth and rearing environments and during mild
weather, outdoor birth and rearing (compared with conventional indoor systems)
resulted in improvements in average daily gain, tenderness, flavor, color and
muscle fiber type. Objective sensory,
shear force and muscle fiber type data indicate that under some, but not all
circumstances, outdoor birth and/or rearing may improve pork quality.
Introduction
Intensive outdoor pig production systems have been
considered in recent years in some parts of the world. These alternatives to traditional slatted-floor indoor systems may become
more common as environmental or animal welfare regulations increase. The North American
swine industry has changed dramatically over the past 10 years as swine farms
were consolidated and the number of swine farms declined. Environmental concerns linked to swine
production have increased in the U.S. and in other countries. In large swine-producing areas, producers
have faced increased costs to meet environmental regulations relative to swine
manure, waste and odor management (Beghin and Metcalfe, 1998). Increased costs for environmental compliance
may limit expansion of confinement farms in the near future. Outdoor swine finishing systems have been
used in European nations and on a smaller scale in the United States and other
countries for several years. Awareness
of animal welfare issues and interest in niche retail marketing opportunities
have contributed to recent increased interest in alternative production
systems.
One reason for interest in outdoor pig production has
been the low capital cost of outdoor systems, which varies from 40-70% of the
cost for conventional indoor systems (Thornton,
1988). Outdoor pig production can
achieve similar gross margins as indoor production systems but with lower
capital investments (Edwards, 1995).
Others have suggested that outdoor pigs have a calmer behavior and are
less susceptible to stress in connection with transport and slaughter (Warriss
et al., 1983; Barton-Gade and Blaabjerg, 1989).
Sustainable agriculture systems are
essential to preserve, protect and improve the environment and the animal’s
experiences. Sustainable swine
production combines production techniques to enhance profits and improve
environmental and socioeconomic conditions on the farm (Honeyman, 1996). Opportunities for niche marketing of
sustainable operations have certainly increased the number of producers
striving to market sustainable, natural, or organic products in the United
States. Many consumers want to purchase
food products from various systems, including organic, free-range,
antibiotic-free or others. Research at
Texas Tech University has focused on the production of Sustainable Pork®
as an animal, environmentally and worker friendly product.
Many studies of environmental effects on pork quality have yielded widely differing conclusions (Edwards and Casabianca, 1997; Sather et al., 1997; Van der Wal, 1991). To date, the effects of diverse birth and rearing environments on pig growth and pork quality have not been carefully or completely dissected.
Consumer Beliefs
and Perceptions
Two surveys were conducted to evaluate consumer
perception on pork products. A Better
Homes and Gardens (BHG) survey prepared by Texas Tech and Successful Farming
Magazine was summarized recently (Freese, 2000). The mail survey included 340 respondents. A Lubbock consumer survey was conducted in
the meat department of three local grocery stores. A total of 220 Lubbock shoppers filled out the surveys. Results
from these two surveys showed that consumers are concerned about animal
production practices. Results showed
that most people want to buy pork from pigs raised in an “animal friendly” and
environmentally safe manner (Table 1).
The BHG survey revealed that consumers said they would pay an additional
10 to 25 cents per pound for this pork.
The question remains if consumers will actually pay a higher price for
these products when purchasing pork.
Consumers from the BHG survey were most concerned with the preservation
of smaller, family farms because 72% of the consumers described themselves as
“very concerned” or “moderately concerned” (Table 1; Freese, 2000) about family
farms. More than half of the Lubbock
consumers indicated that they would be willing to pay more for pork with
certain assurances (Table 1; Gentry, 2001).
Table 1. Survey of
consumers questioned about purchasing preferences of pork.
|
Would you prefer pork with
assurances of: |
Better Homes and Gardensa |
Lubbock Surveyb |
|
From a family farm? |
72% |
- |
|
Worker protection? |
- |
61% |
|
Environmental protection? |
80% |
59% |
|
Animal protection? |
68% |
54% |
aSample size was 340 USA consumers.
bSample size was 220 Lubbock, TX consumers.
Consumers that participated in the BHG survey were
more concerned with environmental and animal protection than consumers that
participated in the Lubbock survey. BHG
consumers (72%) also indicated that they would prefer pork that was produced
from a family farm. Although Lubbock
consumers were more conservative, their responses were still high. However, future studies should be conducted
to determine if consumers will pay more for these products if placed beside
conventional pork products in the grocery store.
Oude Ophuis (1994) compared sensory characteristics
of “regular” and “free range” pork in the United Kingdom (UK). Panelists included individuals with prior
experience of “free range” meat and individuals with no prior experience. Results indicated that labeling and product
experience had a significant influence on the sensory evaluation of “regular”
pork meat compared to “free-range” pork (Oude Ophuis, 1994). Consumers’ perceptions about pig production
systems such as “free range” may influence their organoleptic assessment of the
meat product. In this study, “free
range” meat was perceived as being more tender, juicier and had more flavor
when experienced consumers were aware of its origin. However, no differences were noticed when “free range” pork was
compared to conventional pork in a “blind taste” where the samples were not
identified (Oude Ophuis, 1994).
Other researchers determined that consumers say they
are willing to pay a premium for a pork loin chop with “embedded” environmental
attributes (Kliebenstein and Hurley, 2000).
In this experiment, “embedded” meant that the loin chop comes from a pig
produced in a way in which it could be documented that the potential for
environmental impact was lessened. This
survey included 329 consumers from 5 locations in the United States and 62%
indicated they would pay a premium for the most environmentally safe
product. Some of the environmental
attributes included odor emission, ground water impact, surface water impact or
some combination of these (Kliebenstein and Hurley, 2000).
In conclusion, we are certain that consumers have an
underlying desire to purchase pork products with some social attributes or with
certain social assurances (protection of the environment, the animals, the small
farmer, especially). The consumer
desire is so strong that consumers can attribute enhanced sensory traits to
pork products that they believe have certain social attributes (ex., free
range). A segment of consumers (some
say a niche) say they are willing to pay more for pork products with social
assurances even if improvements in sensory features are not expected or
directly included in the presentation of the pork product. Taking advantage of the willingness of some
consumers to pay more for pork with certain social assurances (protection of
the environment or the animals, especially) is a new concept in marketing pork
products.
Outdoor Housing
Systems
Outdoor housing on pasture or dirt pens accounts for
less than 6% of the pigs finished in the United States (USDA, 2001). These systems usually consist of a large
paddock and shelter for the pigs.
Climatic conditions and land availability are two limiting factors to
consider when producing pigs outdoors.
Several criteria that are often considered when planning an alternative
swine housing system include space allowance, ground cover, group size, and
feeding regime. Alternative systems
typically avoid the use of liquid manure and mechanical ventilation. Other constraints to outdoor finishing facilities
are soil damage, land availability, pollution potential, and the logistics of
supplying daily feed and water requirements in all weather conditions (Edwards,
1999). One
very important factor to consider with outdoor pig production is the correct
choice of location that includes evaluation of soil type and climatic
conditions (Edwards, 1995). Outdoor
housing systems are perceived to be more animal friendly and more
environmentally friendly. If managed
correctly, the outdoor systems can accomplish this, but under poor management,
outdoor pigs can have poorer performance and cause damage to the
environment. Some environmental factors
that must be monitored under outdoor finishing systems are nitrate leaching, soil
compaction, removal of vegetation, and soil erosion (Edwards, 1999).
Deep-bedded
finishing Systems
Hoop-style pig finishing houses have become increasingly
popular in the United States. A hoop
structure consists of 4-foot high wooden sidewalls fitted with steel tubular
arches covered by an opaque UV-resistant polypropylene tarp. Most of the floor area inside of the hoop
building is bedded with cornstalks or other crop residues. The remainder of the floor area is a
concrete slab where feeders and waterers are placed. Group size can vary considerably and usually ranges from 75 to
250 head per building.
Others raise pigs in deep-bedded swine buildings, such as
converted poultry houses or empty buildings.
Deep-bedded growing/finishing systems have been considered as an
alternative and compared with traditional slatted-flooring indoor systems. Converted poultry buildings can hold 500 to
1,000 finishing pigs and are considered an “all in-all out” system. Pigs in these buildings are raised on some
type of bedding (corn stalks, wheat straw, fescue hulls or other crop residue)
and this system is similar to hoop buildings in some ways.
The major
difference between hoop-style finishing and the conventional finishing
buildings with slatted floors are: the
use of bedding, dry manure management, natural ventilation, larger group sizes,
more environmental variation, and low initial investment. There also may be some advantages for the
animal if finished on bedding. Pigs on
bedding show less tail biting, have fewer foot pad lesions, have fewer leg
problems, and tend to have fewer respiratory problems than pigs on slatted
flooring (McGlone, 1999). Research
comparing growth and meat quality characteristics of pigs finished in hoops has
been limited. Lay et al. (2000)
determined that pigs finished in hoops performed fewer abnormal behaviors, had
a greater rate of play behavior, and fewer leg injuries than pigs finished in a
non-bedded confinement system.
Andersen
and Bøe (1999) looked at the effect of straw bedding or concrete flooring for
loose-housed sows on aggression, production and health. They found no significant differences in
aggression, body lesions or production results comparing these two floor
types. However, they did find that sows
housed on bedding had fewer leg problems than those sows housed on concrete
(Andersen and Bøe, 1999). Researchers
have determined that growing pigs prefer to lie on straw under cool
temperatures but prefer bare floors at higher temperatures (Fraser, 1985). Therefore, the potential benefit of bedding
for finisher pigs would be for environmental enrichment. Fraser et al. (1991) determined that the
presence of straw in a pen of finisher pigs ten weeks old reduced rooting and
chewing of penmates. The straw
functioned in providing a stimulus and outlet for rooting and chewing which
resulted in a reduction of these behaviors directed at penmates (Fraser et al.,
1991).
Texas
Tech University researchers examined foot pad and toe lesions on pigs housed on
bedding or concrete slats. Feet were
scored as clear, mild or severe (greater than 25% of the area in a wound). Texas Tech data suggests that pigs housed on
bedding had more severe foot pad and toe lesions (31% vs 9%) than pigs housed
on concrete slats however pigs housed on slats had more overall lesions (55% vs
32%) than pigs housed on bedding (Table 2, Gentry, 2001). Lung lesions were also scored for the same
group of pigs. Overall, the percentage
of clear and lesioned lungs was similar in the two housing systems. However, the percentage of severe lung
lesions was about twice as high among pigs in slatted floor facilities (Table
2, Gentry, 2001).
Table 2. Percentage of Foot Pad/Toe
Lesions and
Lung Lesions on Pigs housed on
bedding or
concrete slats.
|
|
Bedded |
Slats |
|
Feet |
|
|
|
Clean |
68% |
45% |
|
All lesions |
32% |
55% |
|
Severe* |
31% |
9% |
|
Lungs |
|
|
|
Clear |
68% |
76% |
|
All lesions |
32% |
24% |
|
Severe |
6% |
13% |
*% of lesioned pigs’ feet, for
example 31% of the
32% lesions were severe for pigs
on bedding.
Growth and
Composition of Indoor and Outdoor Finished Pigs
Conflicting findings have been reported on the comparisons of indoor and outdoor pig finishing systems. Some researchers have reported that outdoor finished pigs had lower average daily gain (ADG) than indoor finished pigs during the winter months (Enfält et al., 1997; Sather et al., 1997). A summary of experiments comparing the effects of environmental housing on pig growth and carcass measurements is included in Table 3. Enfält et al. (1997) found that outdoor reared pigs had leaner carcasses than indoor reared pigs during the winter months. Sather et al. (1997) found that outdoor-reared pigs had a lower average daily gain than confinement-reared pigs. Outdoor pigs also required 13.5% more feed during the winter months, however rearing environment had only a small effect on carcass lean percentage (Sather et al., 1997). On a carcass dissection basis, confinement-reared pigs were fatter than outdoor-reared pigs (Sather et al., 1997). Another study conducted by Van der Wal et al. (1993) compared free-range pigs with intensive reared pigs and found no significant differences between the two groups in growth or carcass measures.
Beattie et al. (2000) concluded that pigs from
enriched environments (3.5 m2/pig, solid flooring with straw
bedding) had higher levels of backfat (P < 0.05) and higher growth
rates (P < 0.001) during the last stage of finishing (15 to 21
weeks), compared to pigs finished in a barren environment (0.76 m2/pig,
concrete slats). Studies on the
environmental enrichment of pigs have determined that earth-like material (peat
or moss) may be an effective enriching agent (Beattie et al., 1998). In previous studies, environmental
enrichment was only incorporated after weaning (Warris et al., 1983; Pearce and
Paterson, 1993). Hessing et al. (1993)
suggested some characteristics that can affect pig performance and meat quality
such as stress responsiveness are established earlier in life. Others have found that environmental
enrichment resulted in no improvement in productivity (Pearce and Paterson,
1993; Blackshaw et al., 1997). The
nature of the enrichment and the length of exposure to the enrichment may
explain the conflicting findings thus far.
Pork Quality Measures of Indoor and Outdoor Finished Pigs
Researchers in Hungary studied the composition of muscle from pigs finished under “free range” conditions compared to traditional large scale finishing units (Dworschak et al., 1995). Pigs finished under “free range” conditions had muscle with higher levels of zinc and copper that shows that the metal-binding capacity of the proteins in these animals is higher than the control group (Dworschak et al., 1995).
A comparison of the effects of
environmental housing systems on pork color and sensory characteristics are
included in Table 4. Studies have reported reductions in postmortem pH and
water holding capacity in outdoor pigs (Warriss et al., 1983; Enfält et al.,
1997). Loins from outdoor reared pigs
had a lower ultimate pH, higher drip loss and higher Warner-Bratzler shear
force values (Enfält et al., 1997) than loins from indoor finished pigs during
the winter months in Sweden. Meat from
outdoor finished pigs also had more lactate and crude protein, a higher
glycolytic potential, less intramuscular fat and less water (Enfält et al.,
1997). Van der Wal (1991) reported no
differences in pork eating qualities of outdoor reared pigs. Beattie et al. (2000) reported that pigs
from enriched environments produced pork with greater tenderness than pigs
raised in barren environments. Overall,
studies comparing indoor and outdoor finishing systems are inconsistent as a
result of variable climates in research (Table 4). Environmental and management practices play a critical role in
the success or failure of an outdoor finishing system.
Several researchers have
found no differences in pork eating quality measurements comparing pork from
indoor and outdoor reared pigs (Van der Wal, 1991; Barton-Gade and Blaabjerg,
1989). Jonsäll et al. (2001) reported
that ham from outdoor reared pigs was less juicy and acidulous than ham from
indoor reared pigs (P < 0.05) but
no differences were found in tenderness, odor intensity or meat taste between
the indoor and outdoor reared groups.
Maw et al. (2001) reported that pigs housed on straw bedding produced
bacon with a stronger fried meat flavor than bacon from pigs housed on concrete
or slats (P < 0.05). Bacon from straw-bedded pigs was darker in
color than bacon from pigs raised either on contrete or slatted flooring (Maw
et al., 2001). Beattie et al. (2000)
found that pigs from enriched environments produced pork with a lower shear
force (more tender) than their counterparts from barren environments. Other researchers have found no effect of
physical activity on sensory qualities of cuts from the ham and loin (Petersen
et al., 1997; Van der Wal et al., 1993; Essén–Gustavsson et al., 1988), but the
degrees of exercise and enrichment of the environments varied.
Growth characteristics
for pigs finished outdoors or in an enriched environment vary among all
studies. Differences in feed intake and
feed:gain also were variable. Perhaps this is due to the climatic conditions,
the genetic lines evaluated or other factors.
Few differences were detected in loin muscle quality (color or pH) among
the experiments. Shear force values
were higher (tougher) for outdoor finished pigs in three experiments but lower
(more tender) in two other experiments.
Again, results in loin muscle quality between indoor and outdoor (or
alternative) housing systems are variable.
Many other factors could be confounding results such as environmental
conditions, management, diet, genetics or others. Swine producers should consider all of these factors when
choosing a production system to best suit their environment and choose the one
that fits.
Texas Tech University Research
Growth and
Composition of Indoor and Outdoor Finished Pigs
A
recent Texas Tech University experiment evaluated the effects of diverse birth
(outdoors on pasture with farrowing huts vs. indoors in crate) and rearing (outdoors
on alfalfa pasture vs. indoors on slats) production systems on pig growth and
meat quality (Gentry et al., 2001).
Four outdoor pens were built on alfalfa pasture (Figure 5). Long pens (12 m wide by 105 m long) were
designed so that the pigs were required to walk from one end of the pen to the
other since feed and water was located at opposite ends of the pen (212 m2/pig). A hut (10.1 m2) was provided for
shelter. The indoor pens were 2.1 m by
3.6 m and on concrete slatted floors (1.2 m2/pig). Barrows (n = 12 per treatment) were
allocated to each of the environments.
The treatments were as follows:
indoor-born/indoor-finished, indoor-born/outdoor-finished, outdoor-born/
outdoor finished, and outdoor-born/indoor finished. This experiment was conducted to determine if seasonal effects
exist in the outdoor or indoor finishing systems. Animals were slaughtered at a commercial packing plant. Outdoor-born pigs showed growth advantages
on all weigh dates (d 28, 56 and 112) compared to the indoor-born pigs (Figure
1) for the group slaughtered in July.
Outdoor-born pigs had heavier hot
carcass weights and measured
a larger loineye area (P < 0.05).
|
|
|
|
|
|
*
* * * *
Figure 1. Growth traits of pigs born
either indoors (sows in farrowing
crates) or outdoors (sows on
pasture), * = P < 0.05.
Rearing
environment did not have a significant effect on pig growth rates.
Rearing environment had no effect on pig growth
rates. For the group finished during
the winter months (slaughtered in March), outdoor-born pigs were heavier (P
< 0.05) at d 28 and 112 but no differences were detected in final weight or
ADG. In both of the experiments,
outdoor reared pigs had a higher (worse) feed:gain ratio than the indoor reared
pigs. During the winter trial, the
outdoor reared pigs also had a higher (P < 0.05) average daily feed
intake (ADFI) than indoor reared pigs.
Pork Quality
Measures of Indoor and Outdoor Finished Pigs
Subjective color scores
(NPPC, 1999) were recorded on each loin.
Color scores (6 point scale where 6 = dark purplish red, 3 = reddish
pink and 1 = pale, pinkish gray to white) listed by pig birth and rearing
environment are included in Figure 2.
Loins from the pigs born and reared outdoors had the highest mean for
NPPC color score. Figures 3 a, b, and c
include Minolta L*, a*, and b* values for the treatment least squares means of
the group slaughtered in July. Minolta
L* values range from 1 to 100 with 1 = pure black and 100 = pure white and a
lower L* value indicating a darker colored pork chop. Minolta a* values represent red to green colors with a higher
value indicating more red colors and b* values represent yellow to blue color
with a higher value indicating more yellow.
In Figure 3a and 3b, outdoor born and finished pigs had lower L* and higher
a* values than indoor born and finished pigs (P < 0.05). The effect of the treatments on Minolta a*
values was additive (Figure 3b).
Outdoor born and finished pigs had higher b* values than indoor born and
finished pigs indicated more yellow colored pork (Figure 3c., P <
0.05).
Figure
2. NPPC color scores from sampled
pork
listed
by pig birth and rearing environment.
Means
are simple effects. (n = 11 or 12
loins/treatment).
a,bMeans with different
superscripts differ (P < 0.05).
a)
b)
c)
Figure
3. Objective color patterns from
sampled pork listed by pig birth and rearing environment. Means are simple effects. (a) Minolta L* values, (b) Minolta a* values
and (c) Minolta b* values of loins (n = 11 or 12 loins/treatment).
a,bMeans with different
superscripts differ (P < 0.05).
A summary of carcass measurements, color and sensory characteristics of loins from the two experiments comparing indoor and outdoor finishing systems is included in Table 5. Chops from the outdoor-born pigs (slaughtered in July) had more desirable sensory panel scores for flavor intensity (Table 5) and lower shear force values, indicating more tender meat. However, loins from both groups had acceptable shear force values that would be considered very tender by most consumers (Miller et al., 2001).
For the group slaughtered in March, the outdoor born group had more backfat at the 1st and last rib than the indoor born group. Also, outdoor reared pigs had more backfat at the last rib but less marbling on the loineye. Minolta a* values were highest for the pigs finished outdoors, indicating a redder color of the loin muscle. For the group slaughtered in March, no differences were detected in sensory panel scores or shear force.
Additional studies were conducted comparing each of
the following finishing systems:
indoors on concrete slats, indoors in converted poultry buildings on
deep bedding with curtain sides, outdoors on a dirt lot and outdoors on alfalfa
pasture. Results from these experiments
showed that pigs finished in alternative systems have similar carcass and pork
quality characteristics compared to pigs finished in a conventional indoor
system. Outdoor-housed pigs grew faster
than indoor-housed pigs during the warm months (Gentry, 2001). Seasonal differences in growth patterns may
exist with outdoor finished pigs.
Outdoor-reared pigs had heavier carcass weights, less backfat at the
last rib, larger loineye area and higher loin marbling scores (P <
0.05, Gentry, 2001). In addition to
growth and pork quality advantages, loins from the outdoor-finished pigs had
higher scores for initial juiciness (more desirable) and less off-flavor (P
< 0.05) as evaluated by a trained sensory panel (AMSA, 1995; Cross et al.,
1978).
We also collected pork loin samples for a
histological analysis of the muscle fibers.
Pigs are born with a predominance of Type I (darker red) fibers and as
they develop, there is a shift to Type IIA and IIB fibers. In our investigations, we found that pigs in
the outdoor system tend to have more Type I muscle fibers at processing than
pigs born and reared indoors (Figure 4).
This work is still underway, however, the muscle fiber type data
supports the sensory and pork color data collected in our controlled studies.
Conclusions
Overall, results comparing indoor and outdoor pig finishing systems have
been variable. Some reasons for this
variation include differences in pig birth environment, seasonal effects, and
quality of ground or bedding surfaces.
Research from Texas Tech University indicates that outdoor born pigs
have higher growth rates but more backfat.
A possible advantage for outdoor rearing may be linked to increased a*
values and decreased L* values of the loin muscle. Darker colored pork is more desirable for export markets because
of the increase in water holding capacity.
A careful economic analysis should be conducted to determine if
increased backfat and feed:gain that is associated with outdoor finished pigs
could be offset by higher market prices for meat products from pigs finished in
an outdoor environment. Alternative
nutrition research could lead to decreased backfat levels of outdoor finished
pigs. If consumers are willing to pay
more for products that are produced as “sustainable”, “natural” or others, then
these production systems could be very successful in the future.
There are some real differences in
pork quality noted in the literature.
However, differences in pork quality vary among the different
environments that were investigated.
People are willing to pay more for meat products for social reasons,
even if it does not taste different.
Under some circumstances it can taste better. Consumer perception is such that they enter willing to buy pork
products with social assurances and in some cases, consumers may believe the
alternative pork products will taste better.
We can say quite clearly that alternative products do not taste worse
than conventional products. Pork
produced from pigs born and reared outdoors was equal to or better than pork
from conventional systems under some circumstances. Success of alternative production systems will depend on many
factors but consumer “willingness to pay” for these products would certainly
increase economic benefits for these production systems.
Figure 4. Photomicrographs of muscles
from pigs reared indoors (left) or outdoors (right). The dark-stained fibers are Type I fibers. The dark red fibers are Type IIB and the
lighter-red fibers are Type IIA fibers.
Outdoor-reared pigs had more Type I fibers than indoor-reared pigs
indicating an effect of the environment on muscle fiber type development. Outdoor rearing may tend to delay or prevent
the shift in fiber type from Type I to Type II, thus resulting in a tendency,
under some conditions, for a darker red and more tender final pork
product.
Figure 5. Examples of conventional versus outdoor and
alternative finishing systems for pigs.
