In traditional conventional broiler production, the broilers are kept in barren environments at high stocking densities. Generally, the birds have a high growth rate and are generally inactive. Although there is ongoing improvement in the welfare of conventional broilers, the combination of the production environment, fast growth rate and inactivity still presents several health and welfare issues such as leg problems, increased fearfulness, behavioral restrictions and contact dermatitis. Consequently, provision of environmental enrichment has achieved increased attention within recent years as a strategy to increase welfare, activity and health. Environmental enrichment can be defined as “an improvement in the biological functioning of captive animals resulting from modifications to their environment”1. Some of the commonly investigated interventions include increased distance between feed and water, provision of straw bales or chopped straw, use of perches or platforms, changes to the light schedule and reduction in stocking density. Although, it seems logical that increased activity will result in positive effects such as increased muscle- and bone dimensions and bone strength, negative effects or inconclusive results also have been reported. Thus, the provision of straw bales may increase the severity of foot pad dermatitis which further can result in an increased occurrence of bacterial arthritis, tenosynovitis and femoral head necrosis. In addition, a positive correlation between increased exercise/muscle activity and the development of wooden breast has been indicated.
Effects of enrichment on health and bone characteristics
A PhD project2,which was part of the PROHEALTH project experimentally has investigated the effect of enrichment on: the welfare and health of live broilers, with a special emphasis on leg health and included assessment of body weight, scoring of contact dermatitis, gait scores, scratches, leg deformities (varus or valgus) and plumage cleanliness. In addition, post-mortem assessment was performed to evaluate muscle- and bone characteristics, leg pathology, wooden breast and body condition scores overall.
The types of enrichment tested in Ross 308 birds of mixed sex included, 2 increased distances between feed and water (7 m & 3.5 m), maize roughage, vertical panels, straw bales, 2 types of platforms (30 cm & 5 cm) and a lowered stocking density (34 kg/m2). The birds were kept in pens with appr. 500 birds in each pen. The observation period was 35 days.
An effect on gait scores was found in birds from the treatment with lower stocking density having improved gait compared to birds from the 30 cm platform treatment and birds from the control group (Fig. 1). Furthermore, broilers with access to either type of platform had improved foot pad health compared to broilers from the straw bales treatment (Fig. 2).
There was no effect of enrichment on pathological conditions, but there was an effect on muscle and bone dimension. Birds with access to vertical panels had increased muscle width in the lower leg compared to the groups of birds with 3.5 m between their food and water, maize roughage and straw bales. In addition, birds with 7 m between their food and water had an increased distal diameter of the tibiotarsus compared to birds with access to straw bales. There were no observed treatment effects on scratches, plumage cleanliness, leg deformities and body weight. Subsequently, it was concluded that provision of vertical panels and increased distance between resources can result in larger muscle and bone dimension, possibly having a positive effect on leg health. Furthermore, the provision of environmental enrichment did not appear to be a risk factor for wooden breast or bacterial infection3, 4.
Fig. 1. Percentage distribution of gait scores across the experimental groups. Treatments: A- 7 m distance between feed and water; B- 3.5 m distance between feed and water; C- maize roughage; D- vertical panels; E- straw bales; F- 30 cm elevated platform; G- 5 cm elevated platform; H- low stocking density; and I- control.
Fig. 2. Least square mean ± SE scores of footpad dermatitis across experimental groups. Treatments: A- 7 m distance between feed and water; B- 3.5 m distance between feed and water; C- maize roughage; D- vertical panels; E- straw bales; F- 30 cm elevated platform; G- 5 cm elevated platform; H- low stocking density; and I- control.
Effects of environmental complexity on behavior
Another part of the PROHEALTH study investigated the effects of the different types of the enrichment on broiler behavior as the high level of inactivity, in particular, is considered one of the greatest threats to the welfare of broiler along with rapid growth rate and high bodyweight5, 6
Fig. 3. Percentage (mean ± SE) of broilers in the different experimental groups performing active behavior across age. No distinction is made whether the behavior was performed on or off enrichment. w−x Means within age with different letters differ significantly (P < 0.05). Treatments: A- Increased distance-7 m; B- Increased distance-3.5 m; C- Maize roughage; D- Panels; E- Straw bales; F- Elevated platforms-30 cm; G- Elevated platforms-5 cm; H- Lowered stocking density; I- Control’.
As shown in Fig. 3, video recordings revealed that an increased distance between food and water resulted in an overall increase in activity, however, a high degree of variation occurs over the observation period. A higher frequency of comfort behavior in birds on the 30 cm platforms than on any of the other types of enrichment or in the control group was also shown. It was also indicated that increasing environmental complexity can have positive effects on decreasing fearfulness and promoting learning ability in broiler chickens, improving their welfare.
Productivity and Financial Impacts of environmental enrichment for Broiler Chickens
Finally, the study showed that only one intervention improved financial performance (3.5 m between feed and water) above the control, suggesting that most environmental enrichment would have a negative financial impact due to the additional intervention costs, unless consumers are willing to pay a price premium7.
In the future, it will be interesting to compare the slow growing lines with the conventional broilers concerning the parameters discussed here.
1Newberry, R. C. (1995). Environmental enrichment − increasing the biological relevance of captive environments. Appl. Anim. Behav. Sci. 44:229–243.
2Pedersen, Ida Just (2020). Environmental enrichment for broiler chickens – effects on health, welfare and productivity. PhD thesis, UNIVERSITY OF COPENHAGEN, FACULTY OF HEALTH AND MEDICAL SCIENCES
3Tahamtani, F. M., I. J. Pedersen, and A. B. Riber (2020). Effects of environmental complexity on welfare indicators of fast-growing broiler chickens. Poultry Science. 99: 21-29.
4Pedersen, I. J., F. M. Tahamtani, B. Forkman, J. F. Young, H. D. Poulsen, and A. B. Riber (2020). Effects of environmental enrichment on health and bone characteristics of fast growing broiler chickens. Poultry Science. 99: 1946-1955.
5Bach, M. H., F. M. Tahamtani, I. J. Pedersen, and A. B. Riber (2019). Effects of environmental complexity on behaviour in fast-growing broiler chickens. Applied Animal Behaviour Science. 219: 104840
6Tahamtani, F. M., I. J. Pedersen, C. Toinon, and A. B. Riber (2018). Effects of environmental complexity on fearfulness and learning ability in fast growing broiler chickens. Applied Animal Behaviour Science. 207:49–56
7Jones, P.J., F. M. Tahamtani, I. J. Pedersen, J. K. Niemi, and A. B. Riber (2020). The productivity and financial impacts of eight types of environmental enrichment for broiler chickens. Animals. 10: 378