No connection found between residual feed intake and meat tenderness, but producers advised to remain conservative
Selecting animals that eat less but gain well is a growing trend.
Some breed associations and purebred producers offer genetic information on whether an animal is feed efficient, an economically valuable trait. However, there are often concerns that selecting for a single trait could adversely affect others, such as meat quality.
Recent research from the University of Alberta made no connection between residual feed intake and meat tenderness.
This conclusion came from a research team led by Heather Bruce, director of the Meat Education and Training Network (MEaTnet) and a professor in carcass and meat science at the University of Alberta. Working with scientists at the Agriculture Canada Research Centre at Lacombe, Alta., a paper with complete findings has been accepted for publication.
The Beef Cattle Research Council defines residual feed intake as a factor that has been adjusted for growth rate, size and fatness. A low RFI identifies efficient animals that need less feed to grow and fatten at the same rate as animals with a high RFI.
Canadian beef producers have been conservative when selecting for desirable traits, said Bruce.
“We should then pursue selection for low RFI but continue to monitor it in case something happens. Whenever you do single trait selection you have to be careful there are no unintended consequences,” she said.
This round of research focused on residual feed intake in a group of Charolais, Angus and Angus cross steers born in 2014 and slaughtered in 2015.
The cattle were fed according to standard industry practices.
Their individual residual feed efficiency was measured rather than checking their pedigrees to see if they came from lines of efficient bulls.
They were also checked with ultrasound to make sure they had a minimum of eight millimetres of back fat. After slaughter all the cattle met the A grades, and marbling was assessed with near infrared technology for an estimation of intramuscular fat deposits.
“There have been other studies that indicate animals selected for low residual feed intake and increased efficiency produce tough meat. This study did not support that. We were using animals that were selected genetically. This is based upon the animals’ actual performance at this period of time and it did not appear to affect meat quality,” she said.
However, selection decisions should remain conservative.
“Rigorous selection for low RFI might in fact lead to biological changes in the muscle that could in fact change meat quality. We hope to continue those studies in the future,” she said.
Other practices such as aging contribute to tenderness. The meat from the cattle in this trial was aged for 13 days, partly because of timing in their own facilities.
“A look at the wider literature shows 14 days is considered adequate aging for the tenderness of the meat and be adequate for consumer acceptability. Going longer than 14 days and you start to get smaller increments of improvement,” she said.
Some restaurants and retailers promote longer aging, which can infer other benefits to meat. For example, dry aging for 21 days can enhance the flavour.
“Fourteen days will give you adequate tenderness for consumer acceptability if that animal is gong to be tender. Aging does not necessarily have the same results of how much advantage you have. That can change between breeds and the individual animal,” she said.
Research at Bruce’s lab is delving into how other factors affect tenderness.
Connective tissues are one of those factors. For example, rib eyes and tenderloins have low amounts of connective tissue.
Collagen serves as a connector and can look like a honeycomb holding the muscles together. There are different types of collagen that pervade the whole muscle, so it can affect toughness. Large amounts of collagen are often associated with tough meat, along with other factors such as production practices, age of animal, growth rate, use of steroids, breed and muscle type.
Muscles from the front quarter can produce tougher meat in most cuts. Age could be another factor.
“We found out in previous research (the top sirloin) is very tender in animals, but that is a muscle that shows an increase in connective tissue as the animal ages. It changes with animal age. A muscle like the eye of round doesn’t change. It is already tough.”
However, animals in Canada tend to be slaughtered at a young age.
“The younger the animals are in Canada, the more tender most of the muscles are going to be,” she said.
Another quality consideration could be animal weight.
Current carcasses are heavier because there are economic gains to be made in growing cattle bigger.
“We have not looked at the implication of weight at this stage. All we know is younger animals are lighter than older animals, but there has been no real examination in the difference in quality based upon weight,” she said.
The changes could be physiological as the animal works harder to carry the extra weight.
“I think what is happening is, as an animal’s weight increases, some muscles when the animal is not heavy do not work as hard when the animal is heavy. When you put a strain on them those muscles start to become increasingly influenced on connective tissue and cross linking effect,” she said.