Effects of scalding and dehairing of pig carcasses at abattoirs on the visibility of welfare-related lesions

Abstract

There is increasing interest in developing abattoir-based measures to assist in determining the welfare status of pigs. The primary aim of this study was to determine the most appropriate place on the slaughter line to conduct assessments of welfare-related lesions, namely apparent aggression-related skin lesions (hereafter referred to as 'skin lesions'), loin bruising and apparent tail biting damage. The study also lent itself to an assessment of the prevalence of these lesions, and the extent to which they were linked with production variables. Finishing pigs processed at two abattoirs on the Island of Ireland ( n = 1950 in abattoir A, and n = 1939 in abattoir B) were used. Data were collected over 6 days in each abattoir in July 2014. Lesion scoring took place at two points on the slaughter line: (1) at exsanguination (slaughter stage 1 (SS1)), and (2) following scalding and dehairing of carcasses (slaughter stage 2 (SS2)). At both points, each carcass was assigned a skin and tail lesion score ranging from 0 (lesion absent) to 3 or 4 (severe lesions), respectively. Loin bruising was recorded as present or absent. Differences in the percentage of pigs with observable lesions of each type were compared between SS1 and SS2 using McNemar/McNemar-Bowker tests. The associations between each lesion type, and both cold carcass weight and condemnations, were examined at batch level using Pearson's correlations. Batch was defined as the group of animals with a particular farm identification code on a given day. The overall percentage of pigs with a visible skin lesion (i.e. score > 0) decreased between SS1 and SS2 ( P < 0.001). However, the percentage of pigs with a severe skin lesion increased numerically from SS1 to SS2. The percentage of pigs with a visible tail lesion and with loin bruising also increased between SS1 and SS2 ( P < 0.001). There was a positive correlation between the percentage of carcasses that were partially condemned, and the percentage of pigs with skin lesions, tail lesions and loin bruising ( P < 0.05). In addition, as the batch-level frequency of each lesion type increased, average cold carcass weight decreased ( P < 0.001). These findings suggest that severe skin lesions, tail lesions and loin bruising are more visible on pig carcasses after they have been scalded and dehaired, and that this is when abattoir-based lesion scoring should take place. The high prevalence of all three lesion types, and the links with economically important production parameters, suggests that more research into identifying key risk factors is warranted.Keywords: animal welfare, carcass condemnation, pigs, skin lesions, tail lesions ImplicationsAnimal welfare assessment at abattoirs has several advantages over traditional farm-based assessments. However, the extent to which routine carcass processing either masks or enhances the visibility of key welfare lesions is unclear. This research has confirmed that the visibility of loin bruising and tail lesions is improved by scalding and dehairing of carcasses. Mild app...

Pig carcass tail lesions: the influence of record keeping through an advisory service and the relationship with farm performance parameters

“…Thus, weaning of smaller pigs could lead to more challenges in the grower-finisher period and influence the risk of tail biting. A higher prevalence of tail lesions in a batch is also associated with a lower average cold carcass weight (Carroll et al, 2015). Similarly, we found that as the percentage of severe tail lesions increased the average live weight at which finisher pigs were sold decreased.…”

“…Harley et al performed two studies of slaughter pigs in abattoirs in the Republic of Ireland and Northern Ireland and found that 60% to 70% of the observed slaughter pigs had detectable tail lesions on the carcass (Harley et al, 2012b and. Tail lesions are more visible on the carcass, especially less severe bite marks, compared with the live animal suggesting that recording tail lesions during meat inspection is more accurate (Velarde et al, 2005;Harley et al, 2012a;Carroll et al, 2015;van Staaveren et al, 2015). An undocked, uninjured tail at slaughter is considered a gold standard for pig welfare and suggested as an 'iceberg indicator' capable of providing an overall picture of the health/ welfare of pigs (Farm Animal Welfare Council (FAWC), 2009; European Food Safety Authority (EFSA), 2012).…”

Multi-Stakeholder Focus Groups on Potential for Meat Inspection Data to Inform Management of Pig Health and Welfare on Farm

“…The novelty of this project was to incorporate health and welfare indicators in the MI process. The advantages of assessing pig health and welfare at MI have previously been described, ranging from a large amount of data collection, higher visibility of certain conditions, reduced risk to biosecurity and disease transmission compared to on-farm assessments [6,16,17].…”

“…Additionally, participants did not prioritize welfare indicators (e.g., bursitis, tail lesions, abscesses) as they believed they would be visible on-farm, despite the fact that previous research showed increased visibility when recording these welfare lesions at MI [16]. Moreover, MI was considered to offer the opportunity to record "invisible" health indicators at MI, i.e., those that could not be observed on-farm, contributing to the emphasis on health indicators.…”

Stakeholder perspectives on the use of pig meat inspection as a health and welfare diagnostic tool in the Republic of Ireland and Northern Ireland; a SWOT analysis

“…Stakeholders attributed this ease to the relative absence of time constraints and better visibility of the pigs, although in reality this is not often the case [24]. However, while there is value in data collected at ante-mortem particularly relating to animals requiring special attention (or casualty animals), the key information on the health and welfare of the herd must be gleaned from the carcass and viscera post mortem (i.e., at MI) [4].…”