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Relationship between lesions observed on farm and on the carcass and the influence of mixing pigs before slaughter
Lesions on the carcass can be included at meat inspection as indicators of pig welfare on farm. However, it is unknown how well carcass lesions reflect lesions observed on farm and how they are influenced by practices such as mixing in the pre-slaughter period. Three hundred pigs were sent to slaughter over 5 slaughter days. On the morning of slaughter pigs were randomly allocated to one of 3 treatments (n=20/group; 6 focal pigs/group): boars unmixed (MUM); boars mixed (MM) and boars mixed with gilts (MF).
Frequency of aggressive and mounting behavior after mixing was recorded. Skin and tail lesions were scored according to severity (0 – 5) on farm and on the carcass. Skin lesions were also recorded on focal pigs in the lairage. Loin bruising was assessed on the carcass according to severity (0 – 2). Correlations between skin and tail lesions as measured on the carcass and on the farm were calculated. Effect of treatment and time on behavior and lesions were analyzed by SAS V9.3 PROC MIXED.
MM pigs performed more aggressive behaviour than MUM (50.4±10.72 vs. 20.3±9.55; P<0.05) and tended to perform more than MF pigs (37.2±10.77; P=0.06). MM pigs performed more mounting than MF and MUM pigs (30.9±9.99 vs. 11.4±3.76 and 9.8±3.74 respectively; P<0.01). MUM pigs tended to show a smaller increase in skin lesion score from farm to lairage than MF and MM pigs and MM pigs showed a greater increase than MF pigs (P=0.08). However, on the carcass no effect of mixing on skin lesions or loin bruising was found. No correlations were found between aggressive/mounting behaviour and carcass skin lesions and loin bruising. Skin lesion score on the carcass was correlated with skin lesion score on farm (r=0.21, P<0.01). Similarly, carcass tail lesion score was positively correlated with farm tail lesion score (r=0.18; P<0.01).
Mixing boars prior to slaughter stimulates mounting and aggressive behavior, however the increase in these behaviors is not reflected in higher skin lesion or loin bruising scores on the carcass. Carcass skin and tail lesion scores are correlated with those recorded on farm suggesting that such information recorded at meat inspection could be used by farmers to inform their herd health/welfare plans.
Keywords: Carcass lesions; Mixing; Entire male pigs