Producers should prepare their grassfed cattle for slaughter with the same planning as athletes in training for the Commonwealth Games, according to University of New England senior lecturer in meat science Peter McGilchrist.
At the Meat Standards Australia forum in SA last week at Gawler, he said it was important producers were able to maintain high concentrations or build up the stores of muscle glycogen in the final weeks before slaughter.
“We should think about preparing them for their big day and their big race – just don’t tell them what happens at the end,” he said.
“We should know where and when they are going plus what they need to achieve.
“You need to set them up right before they leave your farm and have them as bullet proof as you can.”
Most non-MSA compliant cattle fall out on high pH which causes dark coloured meat.
Dr McGilchrist said research from WA’s Murdoch University and the University of Adelaide showed “nutrition was king”, especially in late spring/summer and the autumn break to avoid discounts of more than a dollar a kilogram.
It was possible, with a small amount of grain supplementation, to increase muscle glycogen levels.
Supplementing 30 megajoules of metabolisable energy extra per day as pasture dried off paid dividends.
In WA, about 1000 cattle were fed 2.5kg of pellets a day with 12MJ of ME and 13-14 per cent crude protein for 14 days.
Although the control and supplemented groups both had dark cutting rates of 3pc, the supplemented cattle had 0.13pc higher muscle glyogen levels, which is significant considering muscle has a maximum of 2pc glycogen. Less than 1pc is needed to ensure no dark cutting.
The $1/day cost of the pellets was made up for in an extra 3kg of carcase weight achieved.
But in SA, where 600 cattle were fed crushed lupins with a 11MJ energy, there was no significant difference in either muscle glycogen or dark cutting incidence.
“Our theory was the lupins with high protein may have been counteracting energy,” Dr McGilchrist said.
He said ensuring adequate magnesium levels was critical at the break of the season when pastures were lush and short.
SA and Tas results show sub-clinical grass tetany is contributing to higher dark cutting rates at the break of season.
“Magnesium acts like a natural sedative for cattle and without enough they release more adrenaline plus have a larger response to adrenaline so burn through muscle glycogen pre-slaughter quickly,” he said.
An experiment is being conducted feeding about 25g/day of elemental magnesium in pellets to cattle on King Island for five days prior to shipment to Tas for slaughter.
“We know is not as simple as putting a litre (of magnesium supplement) in their water every two weeks,” Dr McGilchrist said.
“ We need to work out how much they need experimentally and then get the manufacturers to come up with suitable commercially available products.”