Does Regular Yarding Supress Weaner Growth Rates?

Does the regular yarding, weighing and sorting of weaners in the lead up to slaughter suppress weaner growth rates? At Landcorp’s Stuart Farm in the Te Anau basin some weaners are yarded four to five times before being sent for slaughter over the August to mid-November period.

Staff suspected that the regular yarding was causing stress and pegging back growth rates judging by the appearance of some weaners as the season progressed. There was no hard and fast data to support this observation and theory so manager Mark Bolger set up a trial to see if some facts would support their gut feeling. Last year the main mob of Red-wapiti weaners was separated into three mixed-sex mobs, all of which had an average liveweight of 83.5 kgs at the start of the trial in early August 2015. The first mob of 200 was weighed fortnightly with no new animals introduced as prime weight weaners were drafted off. The second mob, also of 200, was weighed every six weeks, again with no new animals introduced. A third mob was weighed fortnightly and topped up with replacement weaners as prime weight animals were drafted off.

As the trial played out and individual weights were recorded and analysed the reason for the slowing in growth rates of the fortnightly weighed animals became obvious – and not for the reason originally thought.

“The heaviest and fastest growing weaners were killed off first and the ones remaining were lighter so had lower actual growth rates which reduced the overall rate of growth average as the season progressed. In effect it demonstrated that what we were seeing was correct but not for the reason we suspected,” Mark says

Although the trial didn’t conclusively prove any stress-reduced growth rate link Mark and the team have introduced new management to reduce the frequency of yarding and possible stresses that might inhibit growth. This year the weaners were sorted pre-winter into top, mid, and light weight mobs. When the post-winter weighing started in August only the top weight mobs were yarded over the first month, with the mid and lighter weight mobs following on as the season progressed.

“Instead of weighing 3000 weaners each time we’re weighing about 1000 initially and reducing the numbers in the top weight mobs before moving on to the next. It saves time and means each weaner is not being yarded as many times.”

The yarding frequency and growth rate trial will be run again in 2017 with replacement yearling hinds.

“Weighing the same animals each time gives us a true indication on how or if yarding affects growth.”

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