There are number of opposing theories about food withdrawal before slaughter and the amount of carcass weight lost through food deprivation. There are also several conflicting views on the impact on animal welfare.
One school of thought is that the pigs should be allowed access to food at all times, because hunger is a from of animal cruelty, yet others are pointing out an increase in mortality and motion sickness if food-consumption takes place too close to the timeof transport. (read more)Paul Warriss (amongst many others) writes about increase mortality rates in "meat science 2nd edition, an introductory text" if pigs are fed less than 4 hours prior to transport and goes on to recommend a withdrawal of 12 to 18 hours.
Most of the literature available suggests that the loss of weight in the first 12-24 hours is excremental and a reduction of the weight of the liver* which, conventionally, is not a part of the paid weight - i.e. not affecting the income of the supplier. (read more - pork gateway) ( read more - livestocktrail.illinois)
However, there are opposing views, who therefore advocates that the pigs always have access to food up until the time of loading due to the fear of the potential carcass weight loss.
What is certain, is that if the pigs have been fed close to the time of slaughter, the contamination levels will increase in the abattoir. The more content there is in the stomach and the large intestines (Cecum, Ascending -, transverse - and descending colon) the harder the harder the intestineswill be pushed up against the inside of the abdominal wall. Gasses will bloat the large intestine and contamination levels from accidental perforation or laceration of the large intestine or even the stomach will increase exponentially.
*Amongst others, the function of the liver is to balance the requirements for nutrients in the body, which it absorbs from the blood leaving the stomach and intestines after digestion, so the liver will have been depleting to service the bodies requirements in the absence of ingestion.
Even if the intestines are removed without contamination, the severing of the oesophagus at the thoracic/oesophageal hiatus can cause contamination, even when severed at 2 inches from the lower oesophageal sphincter, due to the pressure in the stomach.
The intestines can also fall apart if they are too full at removal, as the pancreas, duodenum and mesentery fat may split not being able to support the weight of the full stomach and intestines.
Moreover, automation is becoming more prevalent both due to cost competition and labour availability. The slaughter robots, have tools that that are placed on the inside of the abdomen cavity in an opening at the pelvic brim and the lower part of the abdomen wall. The robot pulls the tool away from the carcass in a concave, downwards movement. On the outside of the abdomen wall a circular blade is placed to cut through the middle line opening the pig for evisceration. (Watch video) However, if the intestines are pushing too hard against the inside of the abdominal wall, from food content or gasses, the tip of the tool will catch and rip the large intestines causing faecal contamination spilling onto the carcass.
What is often omitted from the discussion regarding food deprivation is bile contamination. Biles functions as a digestive aid to break down fat into fatty acids. This means when there is digestive activity, bile is released from the gallbladder into the duodenum through the bile ducts.
The bile duct connects the liver to the intestines. The hepatic ducts branches out into the liver, so it is not possible to remove the intestines without severing the bile duct, which will cause a spillage of bile onto the carcass if there is digestive activity. Some forms of salmonella can colonise in the gall bladder, so bile contamination is a food safety hazardand is treated the same way in the abattoir, i.e., it is considered a contamination, and it has to removed in the same manner as faecal contamination.
In healthy pigs, that have been deprived of food before slaughter, the incident rates of bile and faecal contamination is very low. 1 - 2 % combined. When the pigs have not fasted the incident rates easily reach double digits.
Whatever the view is on the economics between the two stages of the supply chain, no logical argument can be posed against pre-slaughter feeding is wasteful.
Depending on sources and type of nutrient it takes 4 to 5 hours for the food to fully pass through the stomach and a similar amount of time to pass through the small intestines. The bulk of the nutrients are absorbed in the small intestines and will therefore not be absorbed in the blood stream until 8 - 10 hours after consumption. Further digestion takes place in the large intestines subsequent to it being released from the small intestines, but they majority has already been absorbed in the small intestines.
Atrophy (loss of muscle mass) sets in anywhere between 1 and 3 weeks deepening on sources.
So, the loss of weight is largely either in the intestines or in the liver (which stores and releases nutrients to the body when nutrients are not being absorbed through digestion.
The removal of faecal and bile contamination is chiefly done by cutting off and discarding the contaminated areas. As the contamination is random and accidental the body parts and the weight of them is not a straightforward proportion, but for argument's sake, let’s say that a factory is killing 15000 pigs, the incident level is 10% and the average weight of rectification is 200g (which is a very conservative number) then the waste would accumulate to 300 kg per week, where an incident rate of 2% would result in a waste amount of 60kg. The difference is 240kg which equates to the dead weight of 3 whole pigs. Or stated alternatively ¾ of a load of pigs is delivered to the abattoir a year, just to go to waste.
That's an additional 150 (12 tonnes dead weight, 16 tonnes live weight) pigs that will have to be produced to fill up the food chain, another 150 pigs that have to be transported to the abattoir and another 150 pigs that will have to be removed again from the abattoir. Besides the food waste there is also the consideration of elevated carbon emission, both from rearing, transporting and partly processing.
Rectified carcassThe intestines reduce approximately 20% in weight over the initial period of 24 hours of fasting. If the pig has fasted before slaughter the guts weigh approximately 8.5 kg whereof 33% is manure/gut content. a pig that has not fasted before slaughter will have a weight of 10 kg whereof 45% is manure/gut content. the additional weight equates to approximately 1.5 kg/pig, which on a 15000 kill is a total weight of 22.5 tonnes of additional waste per week. Aside from the carbon impact from the vehicle movements, there is also additional pollution of the gut content and the carbon impact of growing the crops for the feed and transporting them to farm.
The final note on this, is the impact on food safety and slaughter hygiene. The increase in contamination causes an increase of bacterial load and, at times. Though the pathogens are unlikely to cause any food poisoning, it must still be considered bad practice not to reduce the bacterial and pathogenic load as much as possible and offer the consumer the most hygienic process possible.
A higher bacterial load also affects shelf life which could lead to further food waste.
There is no apparent meaningful regulation of this subject, as far as this reviewhas been able to uncover. Most of the legislation and regulatory guidance is concentrated on farm, transport or stunning and killing at the abattoir. Furthermore, the problem may not be solved by adjustment of regulation, as many farming facilities are not set up to segregate the pigs intended to go to slaughter, from the pigs that are staying on farm and need continued access to food. The farming sector is already facing low pig prices and high production costs which gives them little margin to implement improvements with no financial return.
According to euro stat, (ec.europa.eu) 257 million pigs were slaughter in the EU in 2016.
According to we forum, (weforum) 1.4 billion pigs are killed for food on a global basis.
According to swine.extension each kg of carcass weight 6.1 kg of carbon dioxide is emitted. That’s 488 kg on an 80kg pig. According to epa.gov a typical passenger vehicle emits 4.6 metric tonnes of Co2 per annum, so for every 10 pigs killed (assuming the average weight is 80kg and all the parts of the animal makes it to the fork), you can drive car for a year and have the same amount of pollution. From the previous example, if 3 pigs are wasted per week on a 15000 kill, the 150 pigs wasted per annum equates to driving around 16 cars for a full year. That’s 274,133 cars, if extended to the total European kill of 2016, going nowhere for no good reason.
There are obviously generalisations and assumptions in this article, and the article does not set out to give a solution or decide who should carry the cost for rectifying the situation. Perhaps it is a cause that is worth further investigation, grants, and subsidies. Whatever the answer is, there is a bill to pay – leaving things as they are, is passing the bill on to the next generation.
Disclaimer: This article doesn’t set out to give acutely accurate scientific data, but to paint a picture of a challenge there has been around in varying degree for a long time. The data is from various sources on the internet with a reasonable amount of empirical observation added, made by the author in over 20 years in the industry.