Flock Uniformity – A New Poultry Welfare Indicator?

Introduction

The growing increase in the world population and the urbanization poses a major challenge to the food production sector: Increase production and productivity to meet demand, in a sustainable way, without compromising animal health and animal welfare [1].

In poultry production chain, it is also being seen an increase production rate, with improvement of lineage genetics, management and feed composition, in order to decrease the feed conversion rate and increase the proportion of breast muscle/fat [2]. Under this rising production rates scenario, animal welfare (AW) is receiving increasing attention from the authorities, the consumers and NGOS. For that reason, cost-effective monitoring AW systems are of relevance for meat industry [3].

According to Huneau-Salaün, et al. [4], animal-based welfare indicators are more easily collected at slaughter than on farm, conferring to meat inspection an attractive tool to assess poultry welfare. In fact, based on Council Directive 2007/43/EC that lays down minimum rules for the protection of chickens kept for meat production, a monitoring and follow-up at the slaughterhouse must be assured. This monitoring scheme is based on official controls performed by official veterinarians (OV) under the Regulation (EC) No 2019/627. In this context, OV must evaluate the results of the post-mortem inspection to identify other possible indications of poor welfare conditions such as abnormal levels of contact dermatitis (Council Directive 2007/43/EC). Up to now, in Portugal, Footpad Dermatitis are evaluated and scored by routine for each slaughtered batch (100 feets/ batch) as part of post-mortem inspection procedures.

Although several studies had shown the importance of use Footpad Dermatitis (FPDs) as animal-based welfare indicator are not yet completely clear regarding which stage of the process and welfare are related to [5]. For this reason, and due to the increasing importance of welfare monitoring at slaughterhouse, it is a priority demand to evaluate new feasible welfare indicators such as flock uniformity. Reduced AW can be indicated by poor flock uniformity due to either general housing, management or bird health problems. Based on these considerations, the aim of this study was to investigate the usefulness of the parameter “flock uniformity” (FU) as an indicator of AW to be used during slaughter of commercial broiler flocks.

Material and Methods

The present study was conducted in a Portuguese poultry slaughterhouse during January and February 2020. Ante-mortem (AMI) and post-mortem inspection (PMI) were followed for all slaughtered flocks during the study period.

A total of 34 mixed-sex Ross 308 broiler flocks were analyzed. All flocks were raised under similar farm management systems having a medium age of slaughter of 35 days.

For each flock, information from FCI, such as number of animals that arrived the slaughterhouse and density at farm, were observed and registered before the slaughter. During the AMI the dead-on-arrival (DOA) was recorded and the time of permanence on lairage before slaughter (min) was calculated by the difference between the hour of flock arrival at abattoir and hour of starting batch slaughter.

During PMI it was registered the % of total condemnation (TC), the % of TC by disease and the % of TC due to errors related to slaughter process. Per each flock footpad dermatitis (FPD) were scored 100 footpads, being this value also registered.

The classification of FPD severity grade was considered based on the scheme defined in the guideline published by National Veterinary Competent Authority [6]:

• Score 0 – No lesions or small lesions (<1cm), which are only characterized by small discoloration and are not accompanied by hyperkeratosis;
• Score 1 – Small superficial lesions (>1cm), minimally invasive, single or multiple, accompanied by the presence of black papillae and medium hyperkeratosis, without the presence of ulceration.
• Score 2 – Severe lesions (>2cm), with evident thickening and hyperkeratosis, and may be accompanied by ulcers and signs of bleeding.

The causes of condemnation were also registered using the following codes: Aerossaculitis. Cachexia; Celulitis; Enterite; Fever Status; Insufficient Bleeding; Liver lesions; Pericarditis; Skin lesions; Trauma.

To study the uniformity, only 26 from the 34 flocks were analyzed. The following scores were created based on dialogue and opinion with poultry veterinarians’ experts.

• score 1: [0 -2,5% [ of small animals (high uniformity);
• score 2: [2,5-5% [ of small animals (normal uniformity);
• score 3: [5-7,5% [ of small animals (bad uniformity);
• score 4: ≥7,5% of small animals (no uniformity). The score classification was applied to the first 10% of each flock observed after stunning.

Results and Discussion

During this study, a total of 150  035 animals were analyzed. General results mainly collected during AMI and PMI are summarized in Table 1.

In terms of TC, 0.32% of the inspected broilers were totally condemned. Hosseini Aliabad S.A. et al., (2011) in their studies found cachexia as the main cause of broilers condemnation, followed by septicemia and air sac infection.

In disagreement with this study, trauma had just contributed 0.05% of the TC.

DGAV [6] has stipulated the maximum limit to trauma of 2%. In the present study, the condemnation by trauma was the higher cause with 39.25 % of condemnation. The maximum value registered was 1.12% not exceeding the maximum limit. Trauma may be caused by pre-slaughter processes or during the slaughter process. If the trauma has a redder color it can be said that it is recent and a yellower color that it is older than 24 hours. The OV should be aware of this situation because trauma is an indicator of AW only if it is caused during ante mortem steps.

For Salines, et al. [8], the main cause of condemnation was generalized congestion (41.39%), followed by cachexia (24.80%) and skin lesions (20%). In terms of cachexia is similar to this study but the other causes aren´t, at all.

It is natural that there are differences between studies because flocks are raised in different conditions. The important thing is to harmonize the terminology of the causes of condemnation so that they can be compared. Emaciation and cachexia can be easily confounded as fever status and generalized congestion, as it was aforementioned.

The influence of age in FPD was studied and no statistical differences were found. That goes in disagreement with Bilgili, et al. [9] that found a positive influence of age in FPD.

The medium age of slaughter in this study was 35 days and the maximum of 44 days but in the study of Bilgili, et al. [9] the animals were slaughtered at an age of 56 days. This can explain why in the present study age had no influence in FPD in opposite to the result found in the study developed by Bilgili, et al. [9].

Also, no statistical differences were found on the influence of weight in FPD. This result is in concordance with Kapell, et al. [10], but in disagreement with Broom and Reefmann, [11] that found a positive influence of weight in FDP.

In terms of TC, FPD had no statistical differences which disagree with Lopes, (2014) [12] that found a statistical difference between the level of condemnation and the prevalence and severity of FPD.

Regarding to FU, score 1 was not found in broiler flocks but statistical differences were found for score 2, 3 and 4 regarding DOA and TC, as shown in Table 1.

In this study, FU did not affect the DOA, in opposite, to % of TC and TC by disease or condition as it is possible to see from table 1 analyses. The worse the flock uniformity, the higher the TC. This information contrast with the study of Vasdal, et al. [13] that revealed a reduced TC with worse FU.

In addition, in this study no statistical differences were found between FU and FPD scores as revealed Vasdal, et al.

In terms of causes of condemnation, no association was found with FU, but cachexia (p=0.063) was observed in more condemned animals where the FU was worse (Figure 1).

According to Da Costa et al. [14] the fact that this study was made in mixed-sex flocks lows the uniformity of the flock. By opposite, recent studies made by England et al. [15, 16] (20229 shows that the uniformity is higher in mixed sex flocks comparing to single-sex flocks.

In synthesis, MI is an important official control to ensure that animals entering the food chain according to the legal hygiene, health and welfare requirements.

A WI must be import to the surveillance of animal health and welfare but also to indicate the Official Veterinarians that one or other flock requires most attention during inspection.

Additionally, these results showed the potential use of “flock uniformity” as a poultry welfare indicator and as criteria to be used under a risk-based meat inspection approach: The worse the flock uniformity, the more they must be dedicated to the post-mortem inspection on that batch.

More studies must be done to validate this parameter as a potential animal WI.

Click to enlarge

Final Remark: “flock uniformity” can also be seen at the farm level and this output could be introduced in the FCI in order to apply, at the slaughterhouse level, to a logistic slaughter process and a risk-based MI.

Acknowledgments

The authors would like to thank all the poultry veterinarians and personal that transmitted knowledge and helped us during the data collection.

This work was supported by the project UIDB/ CVT/00772/2020 funded by the Fundação para a Ciência e Tecnologia (FCT).