The
              Report

No. 62: Ecchymosis – What Causes It

THE FULL REPORT
This is a summary of a published RIRDC final research report, Ecchymosis – What Causes It? (Pub no. 99/48) by Dr Robert Mulley (phone 02 4570 1438, fax: 02 4570 1383, email: r.mulley@uws.edu.au) and David Falepau, University of Western Sydney, Hawkesbury.  See order form at back for details or visit our website to download the report at www.rirdc.gov.au/pub/cat/contents.html

Introduction

A large number of deer are slaughtered at Australian abattoirs each year. The carcasses from these animals are often affected by ecchymosis (otherwise known as blood splash) and the venison is frequently downgraded or condemned.
The research objective of this study was to determine slaughter systems that could minimise the prevalence of this serious meat quality defect.
 

The experimental approach

The experimental approach involved analysis and review of factors associated with the occurrence of ecchymosis in other livestock species, collection and analysis of case study information from a range of abattoirs where deer are slaughtered, and from these analyses the planning of experiments on techniques used for stunning and exsanguination (controlled bleeding) of deer, sex of deer, time of year that slaughter of deer took place, and various combinations of these factors. Some of the experimental work was conducted in a small research abattoir where slaughter conditions could be controlled, and the outcomes of these trials were then tested under commercial conditions. Carcasses were graded for ecchymosis using the ecchymosis grading chart developed for deer (RIRDC, 1996).
 

Results

A number of different systems are used for the slaughter of deer in Australia. The major differences between these slaughter systems are:
  • whether they were purpose built for animals of only one particular size;

• their capacity to achieve a short (<5 seconds), medium (<10 seconds), or long (>10 seconds) interval between stunning and the initiation of exsanguination;

• their capacity to implement various stunning and exsanguination methods.


From the results of the current study it was concluded that ecchymosis at each of these abattoir types could be reduced, but only if recommendations specific for each type were adopted.

Case studies of deer slaughtered at different abattoirs to determine the prevalence of ecchymosis were conducted.
 

• Of 963 fallow deer slaughtered, 23.1% had ecchymosis > grade 1, and 8.2% had ecchymosis > grade 2 in the left round, which was shown in the current study to be indicative of ecchymosis in the loins and/or other hind leg primals.

• Of 257 rusa deer slaughtered, 14.8% had ecchymosis > grade 3 in the loins.

• Of 94 red deer slaughtered, only 1 had ecchymosis > grade 2 in the round.


In these studies, the fallow deer were slaughtered by electrical stunning in facilities developed for sheep, and the red deer and rusa deer were slaughtered by captive bolt stunning, in facilities developed for cattle.

In abattoirs where the interval between stunning and the initiation of exsanguination was <5 seconds, thoracic stick exsanguination significantly (p<0.001) reduced the incidence of ecchymosis for both electrical stunning and captive bolt stunning. In other abattoir systems, reducing the interval between stunning and the initiation of exsanguination from 25 seconds to less than 10 seconds significantly reduced the amount of ecchymosis regardless of stunning methods (p<0.008), highlighting the importance of this factor.

The method of exsanguination was shown to be a critical factor in the development of ecchymosis. The rate of blood loss using the thoracic stick method was significantly (p<0.001) greater than the gash cut method regardless of stunning method.

There was also a significant (p<0.05) stunning by exsanguination method interaction, with electrical stunning associated with a greater rate of blood loss in thoracic stuck deer, in contrast with the captive bolt being associated with the greater rate in gash cut deer.

The thoracic stick method of exsanguination incorporated into slaughter systems where the interval between stunning and exsanguination was <5 seconds significantly (p<0.001) reduced the amount of ecchymosis even when following electrical stunning. The same effect was observed in slaughter systems where the interval between stunning and exsanguination was >5 seconds but not to the same level of significance (p<0.03).

Restricting the movement of the animal subsequent to the onset of the grand mal seizure induced by the stun was tested, and it was concluded that mechanically limiting the forward extension of a hind limb to less than its maximum potential reduced the incidence of ecchymosis in the round (M. vastus lateralis and M. rectus femoris- the two largest muscles in the round and those most likely to express ecchymosis) and a number of other muscles. It may be possible to design a restraining device that restricts muscle contraction, however it should be noted that any restraint on the animal prior to stunning may compromise it’s welfare.

Ecchymosis was common in the carcasses of deer killed by head only electrical stunning, a method preferred because of compatibility with the requirements of Muslim carcasses in both domestic and export markets. Ecchymosis also occurred in the carcasses of deer killed by captive bolt stunning, if the technique of exsanguination was variable. This study has shown that a number of factors contribute to the expression of ecchymosis in the carcasses of slaughtered deer, and that tailoring of slaughter procedures to suit particular slaughter systems is necessary, to reduce the extent to which ecchymosis occurs.

Recommendations to industry

1.  The thoracic stick method of exsanguination should be incorporated into all slaughter systems used for deer.

2.  Attempts should be made to reduce the interval between stunning and the initiation of exsanguination.
 

a. Ideally, the interval should be less than five seconds.

b. In slaughter systems where the interval can be reduced to less than 10 seconds, captive bolt stunning, rather than head only electrical stunning may be the preferred method.

c. Where the interval cannot be reduced to less than 10 seconds, head only electrical stunning may reduce ecchymosis in comparison with captive bolt stunning. However, when using head only electrical stunning, exsanguination must be initiated within 20 seconds of stunning, or captive bolt stunning should be used.


3.  The minimum voltage required for humane head only electrical stunning of fallow deer is 150 volts for a current duration of 1 second.
 

a. Higher voltages may be used with no adverse affects on ecchymosis expression, and it is possible that a longer stun current duration of 3 seconds may reduce the incidence of ecchymosis in comparison with a 1 second duration.

b. The humane head only electrical stunning of deer assumes correct placement of the electrodes transversely across the dorsal surface of the neck no more than 3cm behind the base line of the ears. The probes should point cranially and must pierce the skin.


4.   The commercialisation of a fallow deer restraining device that limits the movement of the hind limbs to less than their maximum potential after rendering the animal insensible by stunning should be investigated.

5.  Only the minimum number of male fallow deer required to maintain a supply of animals for slaughter throughout the breeding season should be castrated.
 

a.  Culling policies should aim to incorporate non-pregnant fallow deer does into the supply schedule over the breeding season.

b.  The slaughter of entire fallow deer bucks should commence as soon as possible after the peak breeding season but only when aggressive rutting behaviour has ceased.


6.   Fallow deer venison should not be exported as whole carcasses. Carcasses should be further processed to enable the detection and condemnation of meat exhibiting ecchymosis.
a  Where this is not possible, the left round may be inspected for the presence of ecchymosis while attached to the carcass, via the removal of the M. tensor fasciae latae (the small triangular muscle on the outside thigh). Where ecchymosis is detected in the left round of a carcass by this method the carcass should not be exported whole as usually ecchymosis will be exhibited in every other hind leg primal and loin.

7.   When deer carcasses are further processed, venison should not be inspected until after the denvering process, as superficial ecchymosis (grade 1) is often removed.

Other RIRDC deer reports: