PRODUCERS who know their feed as well as their cattle, particularly in relation to the various factions of protein, are well on their way to targeting a kilogram of live weight gain per day in weaners through winter.
That's the word from livestock nutrition expert Tom Thorn, Total Result Ag Consulting in Millicent, South Australia.
Mr Thorn spoke about setting up the feed base for winter weight gain at a recent Meat & Livestock Australia productivity and profitability webinar.
He said the 1kg-a-day target was certainly possible in southern operations, under assumptions including that cattle are fully fed and the feed base is annual, cereal or perennial pasture.
Understanding that crude protein is a mathematical calculation of nitrogen was the first step, he said.
Protein has three fractions: rumen degradable protein, undegradable protein and non protein nitrogen.
"Forage test and have a clear picture of the breakdown of your feed into these three fractions," Mr Thorn advised.
"Take into account all food sources, pasture and supplements."
Then it is a matter of selecting supplements to balance the protein within the ration. Increase RDP and UDP to increase production targets.
How does it all work?
Every food has part of each one of these protein pools. Lupins and peas, for example, have the highest rumen degradable protein, while canola meal has the highest bypass protein and urea is 100 per cent soluble protein.
RDP, UDP and NPN, in balance, drive production and so selection of feed is critical to getting the right result, Mr Thorn explained.
Grass can come at a ratio of protein that is actually detrimental to live weight gain.
Protein that is in excess, or ends up recycled by the animal, is costly both in terms of wasted feed dollars and energy requirements.
As an example, Mr Thorn presented a weaner at 250kg live weight, consuming 6.5kg of pasture dry matter per day at 32pc protein. That animal requires around 0.94 kg/day of protein.
"The ration we are presenting is two times the protein required, or 1.14kg in excess," he said.
"To excrete an extra 1gm of protein, the animal uses 7.3 calories.
"So in this scenario, 8322 calories per day are needed to excrete the excess protein. Converted, that is 34.8 megajoules of metabolisable energy per day.
"And 38MJME makes 1kg of live weight gain."
Some simple measures to avoid exceeding protein requirements include offering ad-lib course stock salt - not blocks as they limit intake at times of high need; offering free-choice mineral lick high in bentonite and offering pasture at the three-leaf stage.
Further, that excess protein is a lost opportunity, Mr Thorn pointed out
It can be converted to weight gain by offering a starch source - wheat or barley. A balance partial mixed ration is also an option if the infrastructure is there, or corn silage or waste sugar products could be considered but be careful with fat content.
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The story Targeting more than 1kg a day in weaners over winter first appeared on Farm Online.