Comparison of Performance of Commercial Conventional and Free Range Broilers

I. INTRODUCTION

Farm animal welfare is an important subject in higher income countries particularly in the EU, Switzerland, Canada, Australia, New Zealand and the USA especially for commercial poultry production. It has been demonstrated that there is a strong relationship between Gross National Income and Animal Welfare Legislation (Van Horne and Achterbosch, 2008). According to Bennett’s (1996) study, 21% of respondents were “very concerned” and another 60% were “concerned” about the welfare and mistreatment of farm animals in food production. Harper and Makatouni (2002) reported that the two main reasons behind the purchasing of free range products were animal welfare and a perceived health benefit.

Consumers identify free range products as more advanced than conventional products in terms of health benefits. Free range broiler production is in its infancy in Australia but is growing rapidly. In the mid-1990s in Victoria, it was estimated that free range broiler production per week was around 1000 birds, with total broiler production around 171,000 per week (less than 1% of total broiler production) (Dixon, 2002). In 2006, free-range broiler production accounted for 4% of total broiler production and today it is around 15% of total broiler production (ACMF, 2011). Free-range broiler production is associated with poorer bird performance, higher feed conversion and higher mortality compared with conventional broiler production. This ‘performance gap’ is not well understood but is thought to be as a result of poorer digestive health, coccidiosis and dysbacteriosis challenge, nutritional inadequacy and variable pasture consumption. These performance challenges contribute to poor economic sustainability in the industry. It is the purpose of this paper to describe performance of free-range and conventionally-reared broilers at the same location, under commercial production constraints. Comparative benchmarking is an important prerequisite to further exploratory empirical or mechanistic research.

Two farms from the same geographical area (1.5 km apart) were selected in order to compare flock performance over time. Placements of day old chicks were synchronized as much as possible using the same donor flocks. Both farms received an identically formulated diet from the same feed mill differing only in that the free-range diet did not contain in-feed antibiotics as per the requirements of Free Range Egg & Poultry Australia (FREPA, 2009). Dead birds were collected and recorded daily. Birds on both farms were weighed at 7, 14, 21, 28 and 35 days. Feed conversion was calculated at the end of each batch for each farm and corrected to 2.45 kg live weight to be able to compare different killing age and final weights. Data were entered into an Excel spreadsheet and exported to JMP v.8 (SAS Software). Production system and age were used as leverage terms in a least square model to explore the main effects of both and interactions between the two on body weight and mortality. As FCR was only known for a whole batch (not by age) the main effect of production system only was explored. Significance was set at P < 0.05 and where differences existed means were separated using Tukeys HSD.

The effects of age and production system on mortality rate and body weight are shown in Tables 1 and 2. There was a significantly higher mortality for free-range compared with conventional production. Mortality rates for the first week did not differ between production systems. However mortality rates from the second week and thereafter were significantly different. Differences in mortality especially in the second week were mostly the result of yolk sac infection. Antibiotic treatment is not allowed in free range broiler production due to FREPA regulations. On the other hand, in a few batches, predator attacks occurred (mostly chicken hawks), and resulted in high mortality due to pack-up in the free range broiler farm when free range broilers had range access.

Differences between growth rates for each production system were significant only from d 28-35, resulting in an interaction (P < 0.01) between age and production system.

FCR corrected to 2.45kg body weight was higher (P < 0.05) in the free range production compared to the conventional production (Table 3). Growth rate was significantly slower in the free range system than in the conventional production system. Birds in the free range production system required 2 more days to reach 2.45 kg body weight than those in the conventional production system.

That free range production systems return poorer performance in broiler chickens has been previously observed. Weeks et al. (1994) showed that conventionally reared broilers had heavier (4.49 ± 0.08kg) body weight than free range broilers (4.08 ± 0.08kg) at ten weeks of age. This performance gap was attributed to the fact that free range broilers perform walking, running and ground pecking behaviours more often than conventionally reared broilers and so the poor performance was associated with increased activity. The results of the study by Weeks et al. (1994) are comparable to the results presented herein where, at 35d, body weights of the conventional birds were around 7.5% greater than their free-range counterparts (Table 2).

Extrapolating the results from the current study to the free range broiler industry in Australia, the impact of this higher FCR in free range production would cost around $8,000,000 per year. Further, the higher mortality in free-range systems may be indicative of stronger disease challenges and/or metabolic disorders.

Considerable demand exists for chicken meat that has been produced under free-range systems and this is expected to grow in the foreseeable future. This demand is partially emotive and linked to anthropomorphic interpretation of intensive animal practice. However, the performance gap is substantial and may not be sustainable in the long-term. The reasons for this performance gap are obscure and further research is required to delineate the effects of the absence of antibiotic growth promoters and the effects of range access. A greater appreciation for the challenges that free-range broilers face, whether immunological, nutritional or behavioural, will allow more appropriate and strategic intervention by producers on one or all of these axes. 

The authors gratefully acknowledge the assistances of free range farm managers Noelene Lewis, Graeme Stewart and conventional farm owner Mark Attard. The study could not have been conducted without the support of Red Lea Chickens and the Poultry CRC.

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