2. BEEF PRODUCTION AND CONSUMPTION

2.1 Beef Production

The Republic of Ireland has a large beef farming sector, with a significant amount of the production going for export. The total cattle population is some 7,800,000. The focus of this study is on the animals slaughtered for domestic consumption, mainly in Local Authority (LA) approved abattoirs, rather than those slaughtered for export.

A total of 1.9 million cattle were slaughtered in Ireland in 2000. The breakdown by age range is summarised in Table 2.1. This shows that whilst 7% of animals were slaughtered in LA Abattoirs for domestic consumption, only 1% of the animals over 3 years, and so more at risk of infection, were slaughtered in LA Abattoirs.

The LA Abattoirs supply about two thirds of the domestic market, with the remainder being supplied from the export approved plants. The latter mainly supply the major supermarket outlets who will normally specify prime beef. It has been assumed that the age profile of animals supplied by the export plants for domestic consumption will be the same as that for the LA Abattoirs. The total number of cattle slaughtered for domestic consumption is estimated to be 205,700 in 2000 (11% of the total).

Information was also obtained on the animals slaughtered in LA Abattoirs in each of the 26 counties of Ireland. This is summarised in Table 2.2 below. The data in Table 2.2 show that 21% of all bovines are slaughtered in Cork, with the remainder spread fairly uniformly over the remaining counties. It is also noted that the total in Table 2.2 is different to the total reported to the CMMS in Table 2.1.

2.2 Location of Dorsal Root Ganglia

Dorsal Root Ganglia (DRG) are peripheral nervous system tissues located within the vertebral column. They would not generally be removed with the spinal cord but remain attached to the vertebral column. What happens to the DRG will depend on how the carcase is divided into different cuts of meat and how these are subsequently used.

The vertebrae along the vertebral column can be divided into four groups: cervical vertebra (7), thoracic vertebra (13), lumbar vertebrae (6) and sacral vertebra (5). There are two DRG associated with each of these 31 vertebrae, one on each side of the vertebrae. It is assumed that each DRG weighs about 0.5 g, so that there is a total weight of about 31 g of DRG in one carcase.

The meat associated with the cervical vertebrae is the neck and this is always sold off the bone. The thoracic vertebrae is the part of the carcase used for chuck or rib steaks and again these are sold off the bone.

The next four vertebrae and rib bones are used for rib roasts. This part of the carcase may be sold as rib on the bone, but is also prepared as a boneless rolled joint or as steaks.　When sold bone-in, it is common for the bone of the vertebral column to be removed, and to leave only the rib bone.　This would remove the DRG.

The sirloin cut includes the 6 lumbar vertebrae and 3 thoracic vertebrae; i.e. 9 out of the total 31 (29%) of the vertebrae and therefore DRGs. It is used to produce both fillet steak and sirloin steak, both boneless, and also T-bone steaks.　Some may also be used for a bone-in sirloin roast, but this is not common.

The final section of the carcase along the vertebral column is the rump, associated with the 5 sacral vertebrae. Meat from the rump is sold off the bone.

2.3 Beef Consumption

This study is focussed on assessing the risk from exposure to DRG particularly from beef products sold to the consumer attached to the back bone. In practice, as noted above, this means either a rib roast or T-bone steak.

The FSAI sent out a questionnaire to all abattoirs in Ireland asking for information on the numbers and age profiles of bovines slaughtered during 2000, and the proportion of beef sold from the abattoir on the bone. Unfortunately, the results of this survey were difficult to interpret, and did not provide the data needed to assess the amount of T-bones or rib sold.

A follow up survey was then undertaken to a selection of abattoirs asking for more detailed information on the amount of rib of beef and T-bones sold. Responses were received from a total of 72 abattoirs from 7 counties. These 72 abattoirs slaughtered 12,133 bovines during 2000, out of the total of 149,530 slaughtered in local authority abattoirs (8%).

Rib of Beef: Of the 72 respondents, 17 (24%) sold rib on the bone but only 6 (8%) sold it with the backbone. On average, these 6 abattoirs sold a total of 58.3 ribs on the bone per week in 2000 at an average weight of 8.3 kg. However, 55 of these were from a single large wholesale butcher which has a significant influence on these results. These results indicate that rib of beef on the bone is produced from 12% of all animals slaughtered. (This assumes that one rib with 4 rib bones is cut from each half carcase).

T-bone steak: 68 (94%) of the 72 respondents sold T-bone steaks. On average 19 steaks of 460 g each were cut from each half carcase. The numbers sold per week ranged from 1 to 1330, the latter being from the same large wholesale butcher as mentioned above, with an average of 73. The maximum possible number of T bones from each butcher was estimated by multiplying the number of animals slaughtered by the recorded number of T bones per carcase. In some cases the respondent had estimated a larger number of T bones sold than the maximum possible from the numbers slaughtered. In these cases the number based on the number of animals slaughtered was used.　With this adjustment, the survey shows that on average 44% of the sirloin section of the carcase is used for T bone steaks.

Customer Survey: In addition to the data from the abattoirs, a survey of beef consumption habits was also carried out by Lansdowne Market Research in February/March 2001. 1200 interviews were conducted among a nationally representative sample aged 15+. The main results of the survey are summarised in Table 2.3. The survey indicates that 40% of all adults ate rib of beef at least once last year, with 30% eating it once a week and 17% once a month. However, much of this would have been bought with the rib bone but not the back bone (this was not differentiated in the survey). For T bone steaks, again 40% of all adults ate this some time last year with 21% eating it once a week and 22% once a month. For all beef products, the survey showed that 67% of respondents eat beef weekly. The survey also showed that a high proportion of people eat out, with 27% eating out weekly and 26% monthly. However, relatively few of those eating out choose either rib on the bone or T bones regularly (20% Sometimes, 33% Occasionally, and 33% Never).

The survey results suggest an unexpectedly high proportion of people eating T-bones and rib of beef frequently. If it is assumed that a weekly consumer eats a rib roast/T-bone 52 times a year, a monthly 12 times and Less frequently 4 times, then with an Irish population of 3.7 million (and assuming 80% aged 15+ - guess) the survey results would indicate that about 42 million T-bone steaks were consumed in 2000. However, it is known that 205,700 animals were slaughtered for the domestic market, and that 44% of these were used to produce T-bone steaks with an average of 38 per carcase. This indicates a total production of about 3.5million T-bone steaks in the year, about a factor of 10 less than that suggested by the beef consumption survey. Thus the survey results seem to have overestimated beef consumption, but the reason for this anomaly is not known. Reducing the percentage of weekly and monthly T-bone eaters from 21% to 1.8% gives a match to the beef production figures, and it is proposed to use this modified result for this assessment.

2.4 Exposure to DRG

In order to estimate the exposure to infectivity in DRG it is necessary to estimate how much of the DRG would be consumed. Two situations need to be considered, a) meat that is removed from the vertebral column by the butcher or wholesaler, and b) meat that is sold to the customer on the bone.

Meat sold off the bone: Some limited trials were carried out to examine whether the DRG is likely to be removed when meat is cut from the bone by the butcher or whether it would remain with the back bone. In this study, carried out by the Department of Veterinary Anatomy at University College Dublin, the vertebral columns removed from four beef carcases were examined for the presence or absence of DRGs. They reported that the only nerve tissues remaining were spinal nerve roots at each intervertebral foramen, associated with which were the DRGs, easily discernible as small brown masses. In all the segments examined DRGs remained on the vertebral column and were not cut away with the meat. The only exception to this was the DRG of the first cervical spinal nerve. This nerve emerges through the lateral vertebral foramen of the atlas on each side. Its DRG lies towards the outside of this foramen. In one instance a portion of this ganglion was removed.

This would suggest that about 1 in 240 (0.4%) of DRG may be cut away with the meat when the bone is removed. Whilst this is useful to confirm the likely range of values, it was only a limited trial and does not provide statistically significant results. It is therefore proposed to assume that 1% of DRG would be cut away with the meat when the bone is removed. This is in line with the assumption made in the UK study, and should err on the side of caution. An alternative case where only 0.1% is cut away with the meat will also be evaluated.

In commercial boning plants, which operate at high throughput, it was thought that DRG would be less likely to be removed than in small butcher shops, where the butcher may have more time to cut residual tissue from the bone for inclusion in mince etc.

Meat sold on the bone: For meat sold on the bone, it is necessary to estimate how much of the DRG contained within the vertebral column would be consumed. There are no data for this and it would be difficult to determine with any certainty. In the previous DRG risk assessment for the UK it was considered that the DRG would not normally be eaten and it was assumed that any DRG present would be consumed 5% of the time. A worst case of the DRG being consumed 100% of the time was also considered.　

Some members of the DRG Task Force considered that 5% was low, as once the meat was cooked the DRG would come away from the bone easily. In addition, there is also the possibility that the bones would be used to make stock. In this situation it is more likely that all tissues would be removed from the bone.

Following discussions with the DRG Task Force, it is proposed to use a distribution of values with a normal distribution having a 95 percentile range from 5% to 95%.　The sensitivity to this range of values will be tested by using fixed values at the limits of this range.

Cooking: It is assumed that cooking will have no effect on the infectivity.