Although processed ruminant protein is still prohibited in the feed of food-producing animals, the possibility of using other by-products such as fat, collagen and gelatine, is being considered.
A very low risk of BSE but the hazard is still there
Since 24 May 2022, France has been classified by the World Organisation for Animal Health as a negligible-risk country for bovine spongiform encephalopathy (BSE). However, the possibility of some asymptomatic cases transiting through slaughterhouses cannot be ruled out. Considering that by-products of these animals are used in animal feed after being processed, precautions need to be taken to keep other animals from becoming contaminated. The experts from ANSES's Working Group are particularly committed to preventing any new spread of BSE agents: “The BSE crisis likely emerged from a very small number of initial cases” they reiterate in their Opinion.
Recommendations to prevent fat from becoming contaminated by prions
The few data that are available suggest that prions, which induce BSE, do not accumulate in the fat of infected cattle. However, this fat may become contaminated by the spinal cord of infected animals, which harbours a large number of prions. When carcasses are split at the slaughterhouse, the knife cuts through the spinal cord and the surrounding fat is therefore exposed via splashing; if used in animal feed, this fat could then transmit the BSE agent.
On the other hand, ANSES's experts consider that fat obtained from adipose tissue that is far from the spinal column or is not exposed to spatter poses a negligible risk and could therefore be used in animal feed. ANSES recommends conducting studies to quantify the contamination of adipose tissue by spinal cord, taking current slaughterhouse practices into account.
Moreover, fat that is collected before the carcass is split or when the spinal cord has already been removed poses a negligible risk of transmitting BSE. Similarly, in animals less than 48 months old, it is highly unlikely that the spinal cord will be infectious and contaminate the fat. The fat of individuals under the age of four years could therefore be used in animal feed.
As for sheep and goats, the Working Group considers that the number of tissues likely to be infected with the agent that causes scrapie, another TSE, is too high. It therefore recommends not using the fat of small ruminants.
Collagen and gelatine: vigilance is required
Bovine collagen and gelatine are produced from the skin and bones of cattle. Their use in the feed of pigs and poultry was authorised in Europe in August 2021. The main point noted by the experts that warrants particular vigilance concerns the use of bones with a high risk of contamination by prions. The Agency therefore recommends not using the spinal columns of cattle over the age of 30 months to produce collagen and gelatine.
This expert appraisal supplements the report on the use of processed animal proteins (PAPs) from pigs and poultry, published in 2021.