THE impact of lairage timing and duration on the meat colour of grainfed cattle is the focus of new research aimed at reducing rates of dark cutting in the beef industry.
Feedlot veterinary and nutrition consultants Matt and Melissa George from Bovine Dynamics are undertaking the project, which has two main objectives – to determine the effect of time of dispatch from the feedlot and duration of lairage at the abattoir, on rumen physiology, muscle glycogen, and carcase characteristics.
Depletion of muscle glycogen reserves due to reduced dietary glucose precursors and/or physiological stress are the primary factors associated with dark cutting in slaughter cattle.
Matt George said while muscle glycogen concentration is maximised prior to departure from the feedlot, the period of time from feedlot dispatch to slaughter may impact muscle glycogen concentration at slaughter, which is an important factor associated with meat colour and ultimate pH of carcases.
Their pair’s hypothesis is that cattle exposed to longer periods of transport and lairage will have higher ruminal pH, higher ruminal temperature, higher ultimate pH, reduced muscle glycogen levels, and darker meat colour.
Dr George said it was hoped the project’s findings would help guide future recommendations for best practice dispatch and lairage of grainfed cattle.
“Most people in the industry have a reasonable knowledge of what contributes to dark cutting, but quantification of it within the context of both cattle time off feed and lairage time is required,” he said.
“An hour spent at home in the feedlot is not necessarily the same as an hour at the processing plant holding yard. With modern transport systems and improved infrastructure, there’s an opportunity to re-examine lairage systems to address dark cutting,” Dr George said.
“For a lot of reasons, especially animal welfare, we believe we can reduce lairage times for some cattle and get better meat quality outcomes at the same time.”
Data from the field
In-field research, conducted through a well-established supply chain involving a NSW feedlot and processing facility, is now complete and data analysis is underway. Research involved 400 head of cattle of a similar breed type and weight.
Two dispatch times from the feedlot were examined – the afternoon before and morning of slaughter; and two slaughter times – morning slaughter and afternoon slaughter.
“This research has generated information that will empower the feedlot industry to make more informed decisions about transportation and lairage,” Melissa said.
Data collected after slaughter included full Meat Standards Australia grading data, and both subjective and objective meat colour measurements. Weather data will also be incorporated in the analysis.
The project is also looking at the effects on total liveweight shrink or carcase shrink, which can have a profound impact on economics.
“We’ll know kill times, when they were graded and duration of chiller time they had,” Matt George said.
“We’re worried some cattle might not always achieve ultimate pH and therefore, getting assigned a dark cutting grade is not necessarily the fault of the cattle or the general plant’s slaughter conditions – it’s actually potentially a chilling duration issue.”
Rumen boluses are also being used in some of the cattle to measure rumen pH, temperature, and activity level, which will allow comparison of cattle in lairage to cattle back at the feedlot.
“From a rumen fermentation standpoint, we can use rumen pH to determine if cattle exposed to longer lairage times are running out of fermentable substrate prior to slaughter,” Melissa said.
The data generated from the rumen boluses will be compared to slaughter data including meat colour, muscle glycogen, and MSA grading.
The work is being funded by grainfed levies through MLA and the Australian Lot Feeders Association. Results will be available later this year.