Last update: March 26, 2012 12:06:48 PM E-mail Print

 

THE WET CARCASS SYNDROME IN SHEEP

J.P.J. JOUBERT, P.G. MARAIS, F.J.C. SMITH & K.S. VILJOEN

Grootfontein Agricultural College and Regional Veterinary Laboratory, Middelburg CP

 

Wet carcasses of sheep have been seen in alarmingly large numbers at abattoirs since 1981 when investigations into this problem were initiated.

Since that date, financial losses suffered by the meat industry as a result of this syndrome are estimated to be about R2 million. These losses were incurred as a result of the condemnation of unacceptable slimy carcasses and the downgrading of trimmed carcasses.

After exhaustive studies, the cause of the problem has been identified as over hydration of thirsty sheep on arrival at abattoirs.

These studies were conducted in collaboration with other scientists of Grootfontein and the Veterinary Field Services. At present a practical method is still being sought to prevent the occurrence of wet carcasses.

As the name implies, wet carcasses do not dry off, but retain a wet glistening appearance. The wetness is due to an accumulation of fluid in the subcutarleous tissues covering the hindquarters, sides, back and flanks of the carcass. It also occurs in the intramuscular connective tissue layers of the flanks and under the shoulder blades. The insides of skins removed from such carcasses also have a conspicuously wet shiny appearance.

Wet carcasses are unacceptable to the consumer not only from an aesthetic point of view, but also owing to poor keeping qualities.

This syndrome must not be confused with oedema, which, unlike wet carcass syndrome, can be observed in the live animal (as a swelling under the skin). Wet carcass also differs from extreme malnutrition since wet carcass has been found to occur even in super Iamb carcasses.

The problem of wet carcass occurs in all breeds. However, since Dorper sheep and Dorper crosses are more commonly slaughtered at a younger age, the syndrome was first noticed in this breed.

Most of the wet carcasses encountered have their origin in the northwest of Kuruman - in the districts of Gordonia, Postmasburg and Hay. However abattoirs in the Orange Free State, the Eastern Cape and the Karoo have also received such carcasses.

Initial investigations failed to elucidate the cause of the phenomenon. The first clue was found at the Port Elizabeth abattoir as well as in a slaughter trial at Upington when it was discovered that the incidence of the syndrome escalated when lick blocks were provided. Hereafter the idea took root that the increased intake of salt stimulated an excessive intake of water and that this over hydration could be responsible for the abnormal wetness of the carcasses.

Two subsequent loads of sheep received at Beaufort West yielded wet carcasses at the rate of 50% and 75%. This finding however confused the issue since no lick blocks were involved and the animals, which had been transported from farms in the district, had received no water or feed at the abattoir prior to slaughtering. It was finally surmised that many of these sheep, which had been collected in the veld, the previous day must have been suffering from a self-imposed thirst when they were kraal led on the farm for the night with plenty of water available. It is after all a well-known fact that sheep may sometimes, of their own accord, abstain from drinking water for a couple of days.

The assumption that an excessive intake of water can give rise to wet carcass syndrome was then tested at Grootfontein. Seventy young Dorper rams were divided into a control group of 20, and two experimental groups of 25 animals each.

Dry milled lucerne hay was provided in all three kraals for the duration of the experiment. The control group received a constant water supply.

Water was made available to the other two groups for three days only, where after it was withdrawn for 52 hours, and supplied again for 18 hours before the sheep were slaughtered. One of these groups received a lick containing salt (28 %), mealie meal and bone meal during these 18 hours.

The result of this experiment was that the control group had no wet carcasses; the group, which received only water during the last 18 hours, yielded 18 wet carcasses, while in the third group, which received water and salt lick, all 25 sheep had wet carcasses.

This experiment therefore confirmed that wet carcasses may well occur when thirsty sheep drink too much water and that a salt lick aggravates the problem.

A subsequent experiment was conducted to confirm these results and to find out how long a wet carcass remains wet before it is restored to normality Once again Dorper sheep were used.

In this case licks did not have much effect on the incidence of the syndrome. The trial however indeed confirmed previous findings and showed that the carcass only starts to dry off after four days.

 

Prevention

At the abattoir: Various trials must still be carried out to determine what can be done about feed provision at abattoir kraals. The provision of hay appears to be problematic in that it causes blockages in the sewage system.

However, at the moment, the provision of dry hay instead of lick blocks at the abattoir seems to be the only practical solution to the problem as water cannot be withdrawn.

It is obviously unfeasible to keep animals at the abattoir for four or more days till the wet carcass condition has passed.

On the farm: The state vet at Upington has received an indication from a few farmers that his advice to make salt licks freely available to stock in the veld has indeed reduced the incidence of wet carcass. These findings will however have to be verified.

It nevertheless remains a good suggestion because, if animals are accustomed to salt licks, they will not take in excessive amounts of lick at the abattoir. They will also drink water regularly and will not have to take in an excessive amount all at once. If this is so, it may be a good way to reduce the incidence of wet carcasses or even to prevent their occurrence altogether.

 

Published

Dorper News 38