Left-overs drive cattle growth rates

Maximising beef cattle growth rates on fodder beet crops requires 25 per cent of the crop to be left behind at each break shift.
Tuesday, 25 July 2017

This is according to Lincoln University’s Dr Jim Gibbs, who says there is a strong correlation between the quantity of beet left behind at each shift and cattle intake.

Speaking at a Beef + Lamb New Zealand’s Central Canterbury Farming for Profit workshop, Gibbs says if 10% of the bulb is left behind then intakes are being suppressed. If the cattle are maximising their intake then 25% of the bulbs will be left behind at each break shift.

“This a whole lot more than what people are used to.”

He says the grazing behaviour of cattle will see them going back and eating the residues in the middle of the night-typically between 11pm and 1am. That means the 25% residual gets eaten over three days and total utilisation is still high – over 95%.

It is these incremental gains in intake that will make the difference between whether or not liveweight targets are met. A 200g liveweight gain improvement only represents about three quarters a kilogram drymatter intake, after maintenance.

He says because of the idiosyncratic nature of fodder beet, many people are not realising the growth potential of their cattle on the crops, which should be 1kg/day or better.  

Liveweight gain reflects intake in beet systems, so beet needs to make up the majority of the animal’s diet.

“At 60% beet you are condemned not to meet your liveweight targets.”

Minimising supplements

This relationship between supplement and fodder beet intake is another quirk of fodder beet. Gibbs says beet intake decreases by more than one kilogram for every kilogram of extra supplement eaten.

“This is unique to beet and is related to the amount of sugar in the bulb.”

In a well-grown crop comprising 25% leaf and 75% bulb, there is sufficient protein in the leaf to meet a cattle beast’s protein requirements.

Where the leaf is damaged, diseased or wilted, extra protein maybe required, especially for R1 cattle, but the best source of this protein is grass.

“If you want to add more protein don’t add fibre – if you add fibre their beet intakes will decrease.”

If a fibre-based supplement is necessary, it should be no more than 1kg/head/day for R1s and 2kg/head/day for R2s.

“If you offer then supplement they will eat it. The harvest cost for stock to eat supplement is low, while for beet it is higher – so they will over-eat supplement. They don’t eat it to balance their rumen, they eat it to make you poor.”

Gibbs especially cautions against the use of bale feeders when feeding supplement as typically a few animals will gorge on – further suppressing beet intakes- while others miss out completely, and then do poorly.

Trouble-shooting

Cultivar selection is important with fodder beet as there are significant palatability differences between varieties.

Gibbs recommends Brigadier for R1 cattle as it is highly palatable and easy for them to eat, as they prefer to knock bulbs over to eat them.

Where liveweight targets are not being met, Gibbs says trouble-shooting should be focused on the factors that are restricting intake.

“Look at what is being left behind, supplement use, and cultivar selection are the big three.”

Yields in fodder beet crops are notoriously difficult to calculate and are typically over-estimated. This impacts on allocation and intake assessments.

He encourages farmers to aim for the good liveweight yields that can be achieved, and cautions against the poor advice sometimes given that winter liveweights aren’t achievable.

“If you want to learn to swim, don’t get someone who can’t swim to teach you. Watching him drown, and listening to his near death experience, won’t help you swim – get around people who can swim”.