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Poult Sci 2008. 87:14-21. doi:10.3382/ps.2007-00154
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ENVIRONMENT, WELL-BEING, AND BEHAVIOR

Economic and Welfare Benefits of Environmental Enrichment for Broiler Breeders

E. H. Leone and I. Estévez1

Department of Animal and Avian Science, University of Maryland, College Park 20742

1 Corresponding author: iestevez{at}umd.edu


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Designs to enrich the environment are crucial in the effort to fully address the biological needs of domestic animals. Although enrichment programs have been shown to improve health and welfare, little is known of their potential for application to commercial broiler breeder environments. We investigated the potential benefits of cover panels for broiler breeder reproductive performance in a commercial setting. This demonstration trial occurred on 5 commercial broiler breeder farms, each with a control and panel treatment room containing approximately 7,000 females and 800 males. Reproductive performance was measured from 25 to 60 wk by the number of eggs laid per female per week as well as weekly fertility and hatchability rates. The location of marked males was recorded weekly to quantify male movement. Access to cover panels improved egg production by 2.1% and maintained better hatchability and fertility throughout the breeding cycle (significant interactions of age and panel treatment) leading to an additional 4.5 chicks/female. Male home ranges, based on minimum convex polygons, were larger in the enriched (259 ± 24.4 m2) vs. control flocks (184 ± 23.1 m2). Providing enrichment in the form of cover panels improved reproductive performance, most likely by increasing males’ mating opportunities and reducing female stress. We found a clear economic benefit to providing enrichment, an estimated $3 million if all breeder houses within the participating company were outfitted with the panels. These results demonstrate that environmental enrichment is not only beneficial for broiler breeder welfare, but can also be economically advantageous, resulting in a win-win situation for poultry welfare and production.

Key Words: broiler breeder • environmental enrichment • welfare • reproductive performance • cover


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Little information is available on the movement and behavior of broiler breeders in commercial settings. Research has shown that young birds have the ability to move quickly across large pens (Preston and Murphy, 1989), and over time birds will visit the majority of the space available to them (Hughes et al., 1974; Newberry and Hall, 1990; Estévez et al., 1997). Historically it has been assumed that adult broiler breeder males set up territories, similar to feral domestic fowl (Duncan et al., 1978; Savory et al., 1978; Woodgush et al., 1978) limiting their movement to a specific subset of the available space and attracting a harem of females (McBride and Foenander, 1962; Craig and Guhl, 1969; Pamment et al., 1983). In support of this hypothesis McBride and Foenander (1962) showed that in a medium-sized flock of birds (n = 80) males tended to use a small amount of the entire space available to them. However, it should be understood that variable and incomplete space-use patterns do not necessarily imply territoriality, because territories are spaces that males aggressively defend from conspecifics (Davies and Houston, 1984). For example, Appleby et al. (1985) indicated that male home ranges in a large broiler breeder flock (n = 4,000) tended to overlap and were highly variable in size, ranging from 16 to 72% of the total available space. This large variability in space use may simply be a result of individual preferences, or it may indicate use of alternative reproductive strategies by males in a situation in which territories may be difficult and expensive to maintain due to the large number of competitors.

Environmental enrichment can be defined as the addition of biologically relevant features to animals’ environment that foster and encourage natural behaviors (Duncan, 1987; Newberry, 1995; Stricklin, 1995) and generally create a greater number of behavioral opportunities (Newberry, 1995, 1999; Newberry and Estévez, 1997; Mellen and MacPhee, 2001). For example, movement patterns can be influenced by environmental enrichment (Leone et al., 2007) leading to improvements in space use (Newberry and Shackleton, 1997; Cornetto and Estévez, 2001a). The benefits of enrichment to chickens are numerous and include encouraging a more-even distribution of animals (Cornetto and Estévez, 2001b), reducing disturbances and aggression (Cornetto et al., 2002), and reducing fear responses and stress (Jones, 1982; Nicol, 1992; Reed et al., 1993; Grigor et al., 1995; Bizeray et al., 2002). In commercial settings such as broiler breeder operations these benefits may translate into improved reproductive success and productive output.

In commercial deep-litter broiler breeder houses, males generally congregate on the litter area, whereas females favor the raised slatted area. This segregation may be exacerbated when males become sexually mature faster than females. Females will avoid this early sexual interest in commercial houses by retreating from the litter area and remaining on the slats (Estévez, 1999; Millman et al., 2000). The reduced number of females in the litter area means fewer mating opportunities for males. This can result in intense competition for access to the few females available and a high proportion of forced copulations. Intense competition ultimately increases female stress and injury and may reduce reproductive performance.

In this demonstration trial we investigated the effects of environmental enrichment by providing cover panels in commercial broiler breeder houses. We measured the resulting impact on reproductive performance from 25 through 60 wk of age and male movement from 25 to 50 wk. We hypothesized that flocks with access to the cover panels would have greater behavioral control over their environment. If cover panels offer opportunities to avoid aggressive interactions, increase male dispersal throughout the house, and attract females to the litter area, then they may reduce or potentially prevent outbreaks of over-mating. This will ultimately reduce female stress, potentially leading to improvements in reproductive performance.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Experimental Design

This extension demonstration project was made possible through a collaborative effort with 5 commercial broiler breeder farms in West Virginia, each consisting of 2 deep-litter floor houses. Each house was 91.4 m long and 12.9 m wide with a total space allowance of 1,170 m2. Each house contained a raised slatted area along each side and a central litter floor 4.3 m wide, with 390 m2 of central floor space. At each farm 1 house was randomly assigned as the panel treatment and the second served as a control. In each treatment house, 20 panels were distributed in a staggered pattern, 1 every 4.5 m in the central litter area (Figure 1Go). Cover panels (Estévez and Newberry, 2001) were constructed of 10- x 10-cm wood planks, measured 70 cm high by 70 cm wide, and placed on two 61-cm-long wooden legs for stability. Chicken wire and black plastic mesh were stapled to the front of each panel to slightly obscure the view through the panels, which has previously been shown to be most attractive for chickens (Newberry and Shackleton, 1997; Cornetto and Estévez, 2001a). To discern any possible influence of the panels on floor eggs, panels were not introduced until after 27 wk of age on 2 farms, when the birds had begun to lay. The remaining 3 treatment houses were outfitted with panels before the arrival of the birds at 25 wk of age.


Figure 1
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  		Figure 1. General layout of the cover panels within treatment houses (figure not to scale); both control and treatment houses consisted of a central deep-litter floor and raised slatted areas along the sides. Male feeders and drinkers were in the litter area whereas female feeders and drinkers, as well as nest boxes, were located on both slatted areas. In the treatment houses, cover panels were placed in a staggered pattern starting approximately 4.5 m from the front door and extending through the central litter area. Control houses lacked cover panel enrichment.

 
Each house initially contained approximately 7,000 female and 800 male 25-wk-old broiler breeders of a roaster line. Males and females were fed and watered in separate lines according to standard management procedures. Flock supervisors recorded weekly production measures from 25 to 60 wk of age; egg production was defined as the total number of eggs set for incubation, and the hatchability of those eggs was defined as the number of set eggs that hatched. Each farmer counted the number of eggs laid in the floor area daily. Monthly fertility rates were determined via candling (Walsh et al., 1995; McGary et al., 2002). Weekly mortalities were recorded for both males and females but due to repeated and nonuniform culls, the data were unsuitable for statistical analysis.

Ten randomly selected males in each flock were individually marked on each wing with circular, laminated, numerical tags using the Swiftack Poultry Identification system (Heartland Animal Health Inc., Fair Play, MO) so that their location in the house could be recorded once weekly from 25 until 50 wk of age. Flock supervisors plotted the location of the tagged males on scaled maps of the house. These location maps were then transferred using a digitizer (AceCAD, Taipai, Taiwan) and the Chickitizer program (Sanchez and Estévez, 1998) into X and Y positions for analysis with ArcView GIS v8 (ESRI, Edlands, CA). Minimum convex polygons (MCP), generated by connecting the peripheral points of observation (Mohr, 1947), were constructed from the locations for each male (Hooge and Eichenlaub, 2000). Males with fewer than 4 observations were not considered in the analysis.

Statistical Analysis

Egg production, fertility, hatchability, and floor egg percentages were subjected to analysis of covariance (ANCOVA) with age as the repeated-measure continuous covariate and panel treatment as a fixed effect. Because each farm housed both a control and a panel treatment house, "farm" was entered as a random block variable in all models. Because no significant differences were found between the treatment houses that received panels at 25 vs. 27 wk (P > 0.05) for any production measure, this factor was removed from all models. Polynomial effects of age and age by treatment were included to fully capture longitudinal trends. Polynomial effects were added to each model until their value increased above P = 0.05, at which point they were dropped. All model residuals were checked against the assumptions of normality and homogeneity of variance.

To understand differences in male use of the slatted area, we classified their locations within the house as either on the litter area or on the raised slats. We then calculated the percentage of time males were observed in each area, at each farm. These averages were tested with a {chi}2 test for differences in slat use between treatments.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Reproductive Performance

Egg production was modeled with a polynomial in which age was significant (F1,323 = 161.73; P < 0.01), as was the panel treatment (F1,323 = 17.75; P < 0.01; Figure 2Go). No interaction terms of age and treatment were significant (P > 0.05). The average number of eggs laid per female for this line of roaster is 155, and the panel treatment houses saw a 2% increase (158 eggs per female). There was a considerable amount of variability between farms, because the estimated variance component was 27.2% compared with the residual variance.


Figure 2
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  		Figure 2. Egg production per female per week for all farms according to age for both the control (black circles and line) and cover panel treatment flocks (gray circles and line). Panel flock hens laid more eggs (increase of 2.1%) than control hens (P < 0.05).

 
Fertility was modeled with a polynomial age term (F1,69 = 91.82, P < 0.01). Although the treatment main effect was nonsignificant (P > 0.05), there was a linear interaction of age by panel treatment (F1,69 = 3.72, P < 0.05). This interaction suggests that fertility peaked later and at a greater percentage in the panel flocks compared with the control flocks (Figure 3Go).


Figure 3
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  		Figure 3. Fertility percentage by age in both the control (black circles and line) and cover panel treatment flocks (gray circles and line). The significant treatment by age interaction can be seen in the difference in slope between the predicted fertility lines for each treatment. The lines statistically diverge after 45 wk of age (P < 0.05) because fertility levels were higher in the panel flocks.

 
Hatchability was modeled with a polynomial in which age (F1,326 = 22.84, P < 0.01) and the linear age by treatment interaction term (F1,326 = 6.35, P < 0.05) were significant (Figure 4Go). This interaction suggests that the effect of enrichment became more pronounced as birds aged. The predicted hatchability percentages began to diverge around 35 wk of age when the difference was 0.5% (87.59 in control flocks vs. 88.09% in panel treatment flocks) and climbed to 2.60% divergence by 60 wk of age (68.24% hatchability in control flocks vs. 70.84% in panel flocks). This hatchability improvement meant that the increase in the number of chicks hatched due to the panel treatment was greater than the mere increase in egg production. Whereas control females produced 126.5 chicks, panel house females averaged 131.0, an additional 4.5 chicks per female. Again, there was a considerable amount of farm-to-farm variability, because estimated farm variance components were 22.73% compared with the residual variance components.


Figure 4
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  		Figure 4. Percentage hatchability observed at all farms according to age for the control (black circles and line) and cover panel treatment flocks (gray circles and line). The interaction of cover and age can be seen in the different slopes of the predicted hatchability regression lines for each treatment over time. The lines significantly diverge after 38 wk of age (P < 0.05) because hatchability was better maintained in panel flocks.

 
Floor egg percentages were modeled with a polynomial age term (F1,1205 = 40.76, P < 0.01) and, although there was a significant effect of the panel treatment (F1,1205 = 69.66, P < 0.01), the interaction term for age by treatment was also significant (F1,1205 = 92.73, P < 0.01). On average, panel flocks consistently laid fewer eggs on the litter floor after 39 wk of age (P < 0.05). It became evident upon closer examination that there was a great deal of variation in floor egg incidence between farms (Figure 5Go). The estimated farm variance was 110.8% compared with the residual variance component.


Figure 5
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  		Figure 5. The percentage of eggs laid on the litter floor on each of the 5 participating farms. Control flocks are in black and panel flocks are in gray. On average, control flocks had a greater incidence of floor eggs than cover panel treatment flocks (P < 0.05). Farms experiencing a high degree of floor eggs (e.g., farm 4) saw the greatest improvement with the cover panels.

 
Male Space Use

Minimum convex polygons were larger in the panel flocks than in the control (F1,82.6 = 6.86, P = 0.01). The average MCP for the control treatment was 184 ± 23.1 m2, whereas males in the panel treatment houses used 259 ± 24.4 m2 (reported as least squares mean ± SEM). For the control birds, this represented 16% of the total house space available, or 47% if they utilized the litter area exclusively, and 22 or 66% usage in the panel flocks, respectively. The range of total space use varied from 1 to 41% for males in the control flock and from 4 to 61% in panel flocks. In addition, males in the panel treatment houses were located more often on the slatted area than males in the control houses: 22.7% of the time vs. 17.0% ({chi}2 = 5.03, P < 0.05).


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
The results of this demonstration project clearly show that environmental enrichment is not only beneficial for bird welfare, in terms of increasing behavioral opportunities, but also can be profitable for the broiler breeder industry. In this experiment we were able to improve reproductive performance, specifically fertility, hatchability, and egg production, by providing environmental enrichment in the form of cover panels. The results of this project stem from basic ethological predictions that providing enriching cover and reducing male-male competition improve welfare and performance. As such, the results should translate well across different broiler breeder strains. Enrichment has been shown to increase behavioral opportunities (Duncan, 1987; Newberry, 1995; Wemelsfelder and Birke, 1997; Leone et al., 2007), reduce aggressive interactions, and promote more-even space use (Cornetto and Estévez, 2001b). Providing enrichment may also decrease the level of stress (Jones et al., 1980; Jones and Waddington, 1992; Nicol, 1992), which has been shown to have negative consequences for reproductive function in poultry (for review, see Jones, 1996). Therefore, a reduction in stress levels related to access to the cover panels may explain the improvements we observed in reproductive performance.

It is important to note that the improvements observed in egg production, fertility, and hatchability cannot be attributed to the common practice of spiking (introducing younger or sexually inexperienced males; Casanovas and Wilson, 1999; Wolanski et al., 2004). Spiking occurred at either 49 or 50 wk of age in both houses at all farms, and by this age the panel flocks already showed significant improvements in egg production, hatchability, and fertility.

Besides the beneficial effects on reproductive performance, providing enrichment in the form of cover panels may positively affect male-female interactions. Sexually immature females may retreat into the slatted area creating high competition between males in the absence of panels. This competition may lead to sexual frustration (Duncan, 1970; Duncan and Woodgush, 1971) and an increased frequency of forced matings, which can cause injury and increase mortality (Estévez, 1999). Panels have previously been shown to reduce this problem (Estévez, 1999). If panels attract females to the litter floor in large numbers (Newberry and Shackleton, 1997; Cornetto and Estévez, 2001b; Leone et al., 2007), this would lead to an increase in accessibility and ultimately reduce male-male competition. We did not collect behavioral observations in this study, and this will have to be specifically investigated in a follow-up study.

Not surprisingly, we detected a great deal of farm-to-farm variability in most of the production parameters measured in this study. This was particularly true for floor eggs; farms with the greatest incidence of floor eggs appeared to experience the greatest benefit from the cover panels (see Figure 5Go). Cover panels are attractive to domestic fowl (Cornetto et al., 2002; Leone et al., 2007), and this attractive nature would expose hens attempting to lay eggs by them to a consistently high flow of traffic. If hens prefer to lay eggs in quiet, disturbance-free environments (Appleby, 1990; Appleby and Smith, 1991; Wall and Tauson, 2002), then cover panels would not provide a suitable site for egg-laying and may in fact deter hens from laying eggs in the litter area. A large degree of variability was detected in reproductive performance between farms. It is likely that these differences are the result of slight variations in environmental quality and management, similar to what has been recorded with broiler performance (Reichmann et al., 1978; Freeman and Manning, 1979; Nicol, 1992; Popova-Ralcheva et al., 2002; Dawkins et al., 2004; Millard, 2004; Zulkifli and Azah, 2004).

The large size of the MCP home ranges measured in this study suggests a considerable amount of overlap between males, regardless of treatment, which was confirmed via visual examination (E. H. Leone, personal observation). This suggests that, similar to other studies (Appleby et al., 1985; Odén et al., 2004), males did not appear to defend exclusive ranges. However, our results clearly indicate that males in the enriched environment had larger MCP and used the slatted area more often compared with birds in the control houses. The larger MCP may be the result of males being more exploratory in an environment that provides them with protective cover, similar to results found in Cornetto and Estévez (2001b). Males may also have found it easier to climb onto the slats in the enriched houses due to the presence of the panels, because the panels provided additional landing surface. Greater use of the available space, whether in the litter area or on the slats in the enriched houses, may have increased males’ chances of interacting and mating with a greater number and more diverse pool of females. Although multiple copulations are not necessary to attain high fertility in the domestic fowl due to the females’ ability to store sperm (Wishart, 1997; Birkhead, 1998), mating with multiple partners will reduce the chance of genetic incompatibility (Sander, 1993), generally resulting in increased reproductive efficiency (Hazary et al., 2001).

Incorporating environmental enrichment in the form of cover panels not only increased egg production, fertility, and hatchability, but also reduced the incidence of floor eggs and increased male dispersal. These improvements translated into substantial economic gains for the farmer as well as for the parent company. In this study, cover panels increased egg production by 31,520 eggs per house; if the panels were installed in all broiler breeder houses of our industry partner, this could translate into an addition 12.4 million eggs per production cycle. The increase in egg production coupled with the improvements in hatchability produced an additional 4.5 chicks per female. With an estimated value of $0.20 per 1-d-old chick, each panel house would average an additional $6,304 in returns, with our industry partner standing to gain $3.3 million per year. The initial $400 cost of outfitting one house with panels is clearly surpassed by the improvements gained in just the first flock. An additional benefit of the panels is that they can be used repeatedly with minimal repairs and easy cleaning.

In conclusion, this study shows that increasing environmental enrichment may not only benefit welfare, providing birds with increased behavioral opportunities and greater control over their environment, but can also positively affect farmer returns. In this demonstration project we have shown that enrichment has the potential to add lucrative economic gains while addressing welfare concerns, offering a win-win situation.


   ACKNOWLEDGMENTS
 
We would like to express our extreme gratitude to Kristen Wilson (Ellicot City, MD), and to the poultry company and personnel that made this study possible.

Received for publication April 13, 2007. Accepted for publication September 13, 2007.


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 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
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