Molting, Bird Density, and Animal Welfare
by Ken W. Koelkebeck
In today's commercial
poultry industry, technological advances in management practices and housing
systems has made this industry very efficient. These improved practices have
benefitted the consumer by keeping prices for poultry meat and eggs at a stable
and low level. However, over the past 35 to 40 years some questions and concerns
have been raised by the general public regarding the intensive raising of poultry
in today's commercial systems.
Today's commercial poultry
producer uses performance measures to determine the profitability and welfare
(well-being) of a flock. The assessment of the well-being or welfare of a poultry
flock is judged differently by some people associated with the animal welfare
movement. These people essentially believe that some of the current methods
of raising and housing poultry do not support their well-being and welfare.
They believe that all poultry should not be caged, penned in large groups, induced
molted, fed antibiotics, or subjected to other current poultry industry practices.
Induced molting and bird/cage density have been two practices that have drawn
considerable attention by researchers in the field of poultry well-being and
welfare. Thus, this paper focuses on research conducted in induced molting techniques
and bird density/cage housing systems and relates this research to poultry well-being
Concern for the welfare of the hen during the molt has been expressed
by animal activists groups, poultry scientists, and commercial poultrymen in
recent years. In a recent review article presented at the First North American
Symposium on Poultry Welfare, Ruszler (1998), presented an excellent review
of the health and husbandry considerations of induced molting. In that article,
he discussed the positive and negative aspects of molting programs and related
them to the concerns about poultry well-being during an induced molt. He mentioned
that early work by Mrosovsky and Sherry (1980) showed that a hen which is undergoing
a natural molt will reject feed for an extended period of time. In addition,
he commented that a broody hen (chicken or turkey) will naturally go for 21
or 28 days consuming little or no feed.
There are several types of induced molting methods employed in
today's commercial egg industry. Most
of these programs involve the use of feed withdrawal (fasting) to produce a
cessation of egg production. Guidelines regarding the specifics of molting programs
have been published by several institutions (Swanson and Bell, 1974; Brake and
Carey, 1983; Ruszler, 1996). These programs recommend using fasting periods
of varying lengths. For example, Brake and Carey (1983) recommended fasting
a flock until they reached a target body weight loss. The length of fast in
this program is usually at least 10 days or more. Other molting programs that
have involved the use of a short feed withdrawal period (4 to 5 days) have showed
that egg performance results can be comparable to those achieved by a traditional
feed removal program (Koelkebeck et al., 1992; Ruszler, 1996). Kuney
and Bell (1989), however, reported that hens that were fasted for 4 days returned
to production sooner than those fasted for 10 or 14 days, but postfast egg production
(36 wk) was lower for hens fasted for only 4 days. Thus, the research conducted
on the use of a short feed withdrawal period are contradictory.
In a study at the University of Illinois (Koelkebeck et al.,
1992), two experiments were conducted to determine the effects of varying length
of feed withdrawal on postmolt laying hen performance. It was of interest to
see if comparable performance results could be achieved by fasting hens for
only 4 days compared to 7, 10, or 14 days. In Experiment 1, commercial laying
hens at 65 wk of age were continuously fed, fasted for 4 or 10 days. The hens
fasted for 4 days were fed a layer ration immediately after the fast and the
ones fasted for 10 days were fed a 16% protein molt ration after the fast until
the hens were laying at a 10% rate of production, then fed a 16% protein laying
ration. Production performance was monitored for 35 wk thereafter. In Experiment
2, two extra treatments were added and they consisted of fasting hens for 7
and 14 days.
In this study, only two birds died during the fasting periods
in Experiment 1 and both occurred in the 10-day fasted treatment. Total mortality
was 13.1, 7.1, and 8.3% for the fed, 4- and 10-day fasted groups, respectively.
Similar mortality results occurred in Experiment 2. Body weight loss for the
4- or 10-day fasted groups in Experiment 1 were 20 and 29%, respectively; while
body weight losses of 18, 24, and 34% occurred for hens fasted for 4, 7, or
14 days, respectively, in Experiment 2. The results for egg production and egg
specific gravity are depicted in Tables 1 and 2. For egg production, no differences
were found between treatments in both experiments when Weeks 5 to 35 were compared,
however, hens fasted for 14 days produced less eggs than those continuously
fed in Experiment 2 when the Weeks 1 to 35 were compared. For egg specific gravity,
the hens given the longer fasting period generally had better shell quality
than those not fasted. Thus, this study documented that egg production in particular
is just as good for hens fasted for only 4 days compared to 7, 10, or 14 days.
However, this study also showed that egg shell quality was poorer when hens
were fasted for a short period compared to the conventional time period (10
to 14 days) (Table 2).
In a more recent study, Minear (1998) compared performance results
from hens fasted for various lengths and fed different diets. In one study,
hens were subjected to the following treatments: 1) hens fasted for 6 days followed
by the feeding of a molt ration every other day for 18 days then feed restricted
on a daily basis, 2) hens fasted for 4 days then fed oats free choice, 3) hens
fasted for 4 days then fed a 10% protein molt diet, or 4) hens fasted for 8
days then fed a 14% protein molt diet. All hens were light stimulated at 35
days from the start of feed withdrawal and they were all fed a layer diet at
42 days following the initiation of fasting.
Table 3 shows the results for mortality and layer performance
from 6 to 10 and 6 to 30 weeks from the start of the molt. Mortality did not
differ significantly between the treatments. The best early egg production occurred
with Treatment 3, but hens in this treatment had the lowest feed conversion.
In addition, there were no significant effects on egg weights or on case weights
(avg. 50 pounds during lay period). Table 4 shows that the hens on the soft
molt (Treatment 1) had the lowest feed cost per dozen eggs. Thus, this study
indicated that hens subjected to a short fasting period will produce adequately
during the lay cycle.
Thus, the studies cited previously indicate for the most part
that satisfactory performance can be achieved from a molting program in which
a short time period for feed withdrawal is used. These results can be achieved
without compromising the birds health due to inducing a molt by feed withdrawal.
However, in order to provide more information about the health and welfare concerns
of feed withdrawal to induce molting, other factors should be examined in addition
to performance results. To provide more information in this area, a recent study
by Webster (2000) examined the behavioral responses of laying hens following
the withdrawal of feed. In this study, commercial hens were induced molted by
feed withdrawal until 35% of their initial body weight was lost. The behavior
of 36 molted and 36 control hens were video recorded on days 1 to 3, 8 to 10,
and 19 to 21 of the feed withdrawal period when the hens reached 15, 25, and
35% body weight loss. The hens that had feed withdrawn were fed a pullet grower
until Day 28 of the feed withdrawal period, then fed a layer ration.
The results of this study showed that second cycle egg production
averaged 15.5 eggs per hen housed to 40-wk postmolt initiation. In addition,
hens that had feed withdrawn had significantly lower mortality (2 vs 12%) than
control hens. The fasted hens showed increased aggression on the first day of
the feed withdrawal period, then exhibited increased standing, head movement,
and nonnutritive pecking on Day 2. Table 5 shows the comparison between hens
fasted and control fed for the 1 to 3, 8 to 10, and 19 to 21 days of the feed
withdrawal period. Basically, these results showed that fasted hens spent less
time at the feed trough and more time pecking at the cage and feather pecking
than control hens. In addition, fasted hens seemed to rest more than control
hens. This study also showed that hens that had feed withdrawn still showed
behaviors that were consistent with alertness.
In summary, the work presented here indicates that for the most
part, today's commercial molting practices
are not harmful on the hen and in fact, maybe beneficial towards her overall
health. More and more commercial layer companies are moving towards utilizing
a molting program that uses a short feed withdrawal period and achieving good
success. Finally, in a recent article, Garlich (1995) stated that the use of
feed withdrawal to initiate a molt is "within
the normal physiological capability of a hen."
Another management practice used in the commercial poultry industry
that has received considerable attention from the animal rights community is
the practice of housing layers and other poultry in intensive housing situations.
Concerns have been voiced on cage housing in and of itself, bird density and
number of birds housed per cage, in addition to the floor space allowance given
to birds housed in large confinement buildings. Some of the research in this
area has attempted to compare intensive cage production systems with those such
as floor pens, aviaries, and get-away cages. This research has focused on production
and well-being factors as the basis of comparison. In addition, the bulk of
the research conducted in this area has focused on the effects of cage population
and density allotted per bird in cages. It has been shown that crowding and
high-density situations can have negative effects on production and well-being
(welfare) of birds themselves. So, the question still remains as to what should
the appropriate cage density be. In the European community strict regulations
regarding cage density has been adopted for laying hen operations (Blokhuis,
1999). A summary of these regulations is depicted in Table 6. This table shows
that the space allotted per bird is considerably more than typical cage situations
here in the U.S. commercial industry (48 to 60 sq. in. per bird). The reduced
cage floor area provided for hens here in the U.S. does not mean that the birds
health and well-being is compromised, however.
Most of the early literature published in this area has shown
that reduced performance will occur if cage stocking density is increased. Adams
and Craig (1985) summarized research conducted from 1971 to 1983 and they found
that reducing cage floor space from 60 in2 to 48 in2/hen
reduced eggs per hen housed by 16, reduced feed consumption 1.0 g/hen/day, and
increased mortality by 4.8%. In a study conducted after this review article
was published, an analysis of 23 different production variables was conducted
with laying hens (Koelkebeck et al., 1987). In this study, production,
physiology, and behavior parameters were measured for laying hens maintained
in deep and shallow cages at two densities and three cage populations. Tables
7 and 8 depict the results. It is interesting to note that improved livability
was noted for hens given 54 vs 72 in2/hen. In addition, production
differences were not seen between the space allotted per hen and cage population
size. More recently, production performance results affected by space allowance
per hen was reported by Anderson (2000). The results of the 33rd
North Carolina Layer Performance and Management Test reported that egg production
was reduced for hens given 48 vs 64 sq. in. per bird (Table 9).
More recent work done in the area of space allocation for layers
and the effect of bird density on performance and laying hen well-being (welfare)
has ben the work on the Edinburgh Modified Cage (Appleby, 1998). In this research,
a modified laying cage was developed for use in European laying hen facilities
in response to public and legal pressure for improvement of laying hen welfare.
In this study, a cage was designed that had a perch, nest box, and dust bath
(Figures 1 and 2). The results showed that the physical condition of the birds
were improved compared to control birds in conventional cages. However, because
of the increased space needed for the perch, nest box, and dust bath, egg production
costs were more than in conventional cages.
In summary, bird density allocation for laying hens and growing
birds is an important consideration for the commercial poultry industry. If
animal welfare concerns demand that more space be given to poultry in intensive
management systems or cages for laying hens be abolished, then production costs
associated with these changes would be dramatically increased.
Adams, A.W., and J.V. Craig, 1985. Effect of crowding and cage
shape on productivity and profitability of caged layers. A survey. Poultry Sci.
Anderson, K.E., 2000. Results of the 33rd North Carolina
Layer Performance and Management Test. North Carolina State University. February
Appleby, M.C., 1998. The Edinburgh modified cage: Effects of group
size and space allowance on brown laying hens. J. Appl. Poultry Res. 7:152-161.
Blokhuis, H.F., 1999. European regulations for laying hens. Presented
at European Symposium on Quality of Eggs and Egg Products. Bologna, Italy.
Brake, J.T., and J.B. Carey, 1983. Induced molting of commercial
layers. North Carolina Agricultural Extension Service Poultry Science and Technical
Guide No. 10. North Carolina Agricultural Extension Service, Raleigh, NC.
Garlich, J.D., 1995. Study: Hens are unaffected by fasting during
forced molt. Poultry Times, Feb. 27:13.
Koelkebeck, K.W., M.S. Amoss, Jr., and J.R. Cain, 1987. Production,
physiological, and behavioral responses of laying hens in different management
environments. Poultry Sci. 66:397-407.
Koelkebeck, K.W., C.M. Parsons, R.W. Leeper, and J. Moshtaghian,
1992. Effect of duration of fasting on postmolt laying hen performance. Poultry
Kuney, D.R., and D.D. Bell, 1989. Effect of molt duration on performance.
In: Proceedings of the University of California Poultry Symposium, University
of California, Riverside, CA.
Minear, L.R., 1998. Molting hens the lite way. Presented at 1998
Multi-State Poultry Feeding and Nutrition Conference, Indianapolis, IN.
Mrosovsky, N., and D.F. Sherry, 1980. Animal anorexias. Science
Ruszler, P.L., 1996. The keys to successful force molting. Virginia
Cooperative Extension Service, Publication 408-026 (revised), Blacksburg, VA.
Ruszler, P.L, 1998. Health and husbandry considerations of induced
molting. Poultry Sci. 77:1789-1793.
Swanson, M.H., and D.D. Bell, 1974. Force molting of chickens.
II. Methods. University of California Leaflet 2650. University of California,
Webster, A.B., 2000. Behavior of White Leghorn laying hens after
withdrawal of feed. Poultry Sci. 79:192-200.
TABLE 1. Duration of fasting and egg production
||Hen-day egg production
||-- (%) --
a,b = P < .05
Adapted from Koelkebeck et al. (1992)
TABLE 2. Duration of fasting and egg specific
||-- (g/cm3) --
a,b = P < .05
Adapted from Koelkebeck et al. (1992)
TABLE 3. Mortality and layer performance
||Performance (6-10 wk)
||Performance (6-30 wk)
||H-D Egg Prod.
||H-D Egg Prod.
|1 (6-d fast-molt)
|2 (4-d fast-oats)
|3 (4-d fast-10% P)
|4 (8-d fast-14% P)
Adapted from Minear (1998)
a,b = P < .01
x,y = P < .10
TABLE 4. Economics of molt programs for
30 weeks postmolt
||-- (lb/hen) --
||-- (cents/doz.) --
|1 (6-d fast-molt)
|2 (4-d fast-oats)
|3 (4-d fast-10% P)
|4 (8-d fast-14% P)
|Adapted from Minear (1998)
TABLE 5. Behavior of hens not fasted vs
||-- (% observations) --
|Adapted from Webster (2000)