Better Pork - August 2007

Cover Story

The mystery of the disappearing loin – is disease the culprit?

Since peaking in 2005, loin depth has been dropping across Ontario. With genetics, feed and other possible explanations ruled out, the experts suspect that the recent disease outbreaks that have afflicted Ontario herds may be the cause

by KATE PROCTER

Loin depth is one of the key characteristics that pork producers strive to increase because they are paid a premium for pigs with larger loins. So why has the average loin depth across the province dropped dramatically since the first quarter of 2005?

It’s a complicated issue, but perhaps the most likely culprit is disease.

Ontario pork producers have been battling several serious diseases over the past few years, including PRRS and circovirus. While the most obvious effects have been on increased mortality and morbidity rates and an increase in medication costs, the higher incidence of disease may also be having an effect on carcass characteristics.

Chris Hills works for Wallenstein Feed and Supply Ltd. He helps his customers analyze market hog data using Ontario Pork’s Online Information Network Knowledgebase (OINK). He often looks at the data and suggests to producers how marketing might be done differently to help them take advantage of premiums offered by the packers.

One of his clients came to him with a concern that the loin eye area of his hogs seemed to be decreasing steadily over time. Loin eye is a measurement of the meat in a pig’s back that makes up the pork chop and one of the key factors that those in the industry strive to maximize.

Hills took a look and discovered that the loin eye area of his producer’s stock was indeed declining. There had been eight turns through this particular barn over the span of about three years that seemed to show a steady decline. The market weight of the animals was not significantly different, but the average loin eye size had dropped from a high of 64.7 millimetres to 57.6 millimetres on the last group. “That’s huge!” says Hills.

The producer had changed genetics, but had switched to a line about three years ago which should have improved carcass quality. Hills contacted the genetics supplier and got recommendations for feed, but it has not made a difference. The producer has several other barns that are not using Wallenstein feed and they are all experiencing the same drop in loin eye area. 

Hills was curious and raised the question among colleagues in the industry. He discovered that his producer was not alone and that data from Ontario Pork revealed that there had been a steady decline in loin eye area for all pigs marketed across Ontario since the first quarter of 2005. 

In the same quarter of 2000, the average loin depth of pigs marketed in Ontario was 56.61 millimetres. It has increased every quarter until the first quarter of 2005, to a high of 63.17 millimetres, at which point it started to fall and has dropped each quarter since then to a low of 60.26 in 2006 (see chart 1). This is significant because it is not about one producer or one month. It is a measurement of all the pigs marketed in the province over the span of many months.

Lost premiums
Joe Aarts has seen a similar trend in his Kintore-area finishing operation. In June 2006, he marketed a group of 1,000 animals with an average loin eye measurement of 60.82 millimetres. The group he sent in October 2006 measured 58.8 and February 2007’s shipment averaged 58.2.  His last shipments, sent in May and June, were up slightly and measured 59.29 millimetres.

Aarts says that he has had problems with circovirus and began vaccinating all his supplier pigs at weaning. The last group that he marketed were all vaccinated and had no disease pressure at all, he explains. So, if the reduction in loin size were caused by disease, he would have expected it to be back up to his historical average on that group.

Aarts has not changed his feeding program, his stocking density is the same and he says that pigs are being raised in exactly the same way. “We don’t change much in our operation,” he says. 

Loin size matters to producers because most are paid a premium based on the size of the loin. While individual contracts will vary, Aarts is paid a premium of $1.25 for a loin between 50 and 54 millimetres, $2 for a loin between 55 and 60 millimetres and $3.50 for a loin over 60 millimetres. On 1,000 pigs which fell below 60 millimetres, Aarts lost $1,500 on the group in loin premiums alone. 

Jason Hutchinson, Maple Leaf’s director of risk management and procurement, explains that over the period of time in question, the specifications and premium schedule have not changed. In their Signature Buying Program, premiums are paid on loins that are larger than 50 millimetres and discounts are taken on those below.

For hogs with a backfat between 15 and 20 millimetres, a premium of $1.25 per animal is paid for loins between 50 and 54.99, $2 is paid for loins that are between 55 and 59.99, $3.50 for loins between 60 and 70. The target is a loin eye depth of 65 millimetres.

 “My first response would be that it has something to do with the health problems we’ve seen,” says Dr. Kees de Lange, a researcher in the Department of Animal and Poultry Science at the University of Guelph.  However, he adds, there could be many other factors influencing this pattern, including a change in the grading system, protein or toxins in the feed and management.

Genotype is the number one factor influencing loin eye area, explains de Lange.  Nutrition and environment should allow pigs to show their performance potential and genotype has not changed dramatically enough in Ontario to result in the decrease shown by these numbers. As de Lange points out, all breeding companies are racing to increase loin eye area, not influencing it to become smaller. “I would rule out quite quickly that genotype is driving this dramatic change,” says de Lange.

Disease can certainly have an influence on loin eye area – by as much as 30 to 40 per cent, he adds. “If you make a pig sick, you can see a dramatic reduction in lean growth and muscle development.”

If this was caused by a problem with feed, de Lange says he would also expect that feed conversion would be negatively affected. In other words, pigs would have to consume more feed to achieve the same amount of gain. In which case, de Lange would expect the feed companies to be searching to find something that was wrong with their feed.

Vaccines also stimulate the immune system, explains de Lange, which would result in a very minor reduction on the amount of lean deposited, but the effect would wear off in about three to four weeks, he says. He thinks the original illness is the cause of the decline, not the vaccine.

Spikes up and down
Frank Wood, hog procurement manager for Conestoga Meat Packers Ltd., says the data seen in his plant has been fairly consistent. There was a noticeable spike in loin eye area in 2003 then it came back down again. “We have gone through periods with spikes both up and down that appear to be associated with periods of circo, extreme weather changes and poor corn,” he says.

Wood says he reviews this data on a monthly basis and also has a few producers that monitor it and alert him to any abrupt changes. If something strange shows up, there is a set of procedures that he follows in order to find out why. The first step is to check the probes, the techniques and the graders on the plant floor.

Wood explains that in a plant like Conestoga’s, which only processes 300 pigs per hour, it is easier to do a visual examination of the carcasses than in larger plants with more animals going through the line at a faster rate. Conestoga works directly with the Ontario Pork Grading Authority to ensure that the grading is being done correctly.

Wood then looks at the ratio of gilts to barrows. Barrows tend to grow faster and deposit more fat and less lean tissue than gilts. This could have an impact on overall numbers if a higher than normal percentage of barrows comes through the plant. Statistics are not available, according to Ontario Pork’s Patrick O’Neil, which compare the number of gilts to barrows that are marketed in Ontario.

Wood also considers various factors, including feed quality, animal health and weather to determine why the size of the loin might be higher or lower. He points out that there is a degree of seasonality to loin size. “Year over year, muscle and fat levels seem to rise and fall at the same time every year,” he says. He can tell when the pigs start eating new corn in the fall, as they tend to deposit more fat and less lean. In the summer, Wood sees bigger loins than in mid- winter. Loin sizes dip slightly in May and again in December.
Health can also have a huge impact, Wood agrees. If disease hits young animals it affects their whole growth cycle. 

If Wood sees a problem with one producer’s animals in the plant, he first rules out any possible grading issues. If the yield is not great, Wood says he then invites the producer, genetics supplier and feed supplier in to work together and sort out the problem. If the problem is bigger than just one producer, Wood consults other industry people to try and identify what is happening. 

Wood cautions against trying to pick one specific factor as being the cause of loin eye variations. “It is so complex, I can’t see anyone saying it is just one thing,” he notes. Even farms that have a lot of labour changes can see an effect on loin eye. It takes time for new employees to learn when they start a new job and this can have an impact. In one example, Wood cites three barns finishing pigs from the same source. The pigs from two of the barns were putting pigs out with average loin size of 64 or 65 millimetres, while the pigs from the other barn were coming out at 56 millimetres. The difference was obviously not caused by genetics, but was a management problem, he notes.

Genetics not the culprit
For her part, Dr. Cathy Templeton, a swine specialist from Listowel, suspects that there may have been some health problems that resulted in the Ontario data. She points out that, while young pigs which get sick may exhibit compensatory growth later on, they do not necessarily deposit lean tissue in the same way as they would have if they hadn’t been sick.

Templeton agrees that genetics in Ontario have not changed enough over the past year and a half to result in a sharp decline in loin eye area. She has seen disease outbreaks cause problems like this before. “In addressing the whole circo virus problem, we have focused on mortality and culling, but it may be a lot more involved than we thought,” she says.

Brian Sullivan, general manager of the Canadian Centre for Swine Improvement, looks at the data from five pure bred herds that market at least 500 hogs per quarter. He says a lot of variability between herds is not unusual. He is not concerned about the decrease in loin eye area that Ontario producers have experienced and predicts that it will come back up to the trend line.

Sullivan points out that on the breeding side there has been a huge increase of loin eye area in a relatively short period and the gains have not shown any sign of slowing down. Average loin eye size has increased to 63 millimetres in 2005 from 56 millimetres in 1998. “I doubt whether the blip is because we are nearing the limit,” he says.

He points to the example of dairy cows, which now produce two or three times as much milk as they used to and are still increasing the amount they are capable of producing.  While Sullivan acknowledges that something is happening, he does not think it is due to changes in genetics. Commercial producers aren’t changing genetics to make that happen. It is more likely caused by something environmental, he says. 

Dave Vanden Broek, general manager of Ontario Swine Improvement, agrees that genetics would not produce the rapid change that Ontario producers have seen. “It is like somebody flipped a switch,” he says. Disease could have that effect, if it was widespread, he adds.

He suggests that a study looking at the timing of the worst incidences of circovirus in Ontario, and also at when the vaccines were made widely available to Ontario producers, would help pinpoint if these disease issues have resulted in the loin size decrease.

Although people are speculating at this point, Sullivan says there is evidence that disease early in the life of a pig limits its lean growth potential. Given the number of disease challenges such as circo and PRRS that have been hitting Ontario nurseries in the recent past, Sullivan says disease is a reasonable explanation for the decrease in loin size, but he doesn’t know how to prove it.

A combination of low market prices, lower output and higher costs related to sickness and the high price of feed may also complicate matters. Sullivan ponders the possibility that producers, facing difficult financial times, could have compromised the nutrition of their animals, which would also play a role in reducing loin size.

Accuracy of grading is another theory that has been suggested, but Sullivan doubts this is the problem. He says that problems with grading would likely result in more fluctuation from quarter to quarter rather than a steady downward trend across the province. “You wouldn’t expect the whole trend to change,” he says.

The Ontario Pork Grading Authority (OPGA) oversees grading at all pork processing plants in Ontario. General manager Dan Bazinet explains that OPGA’s mandate is to represent both the packer and producer equally.  Its role is to provide a third-party audit with no bias one way or the other.

Bazinet says that there have been no grading changes recently and that OPGA is using the same protocol as always. There could be variances between the packers, who may have different preferences depending on the market they are aiming for. “Some packers prefer heavier hogs and that would affect loin size,” he says.

Bazinet says that OPGA has developed rigid systems for ensuring grading accuracy, monitoring each individual grader at each plant. “We are very confident that the grading system here is as accurate as humanly possible,” he says.

Sullivan has looked at data from Alberta, where pork producers have not been hit as seriously with circovirus and PRRS as their Ontario colleagues. “From the sample of Alberta data that we have, we don’t see a change in the trend in lean (loin) depth. It is tending to increase over the last four years that we have data,” he says.  He points out that Alberta’s average loin depth did not get as high as the Ontario data shows for 2004 to 2005, but 2006 and 2007 so far show measurements a bit higher than Ontario’s. The data from Alberta covers about 100,000 hogs per year.