Reflecting on a ‘bearing' season
In the August edition of Vetnotes, I commented that we hadn't seen many bearings at that point in the season - whoops - how things changed as the April-mated flocks started to get close to lambing.
Looking back on the autumn that was, the bearing ‘storms' seen on some properties were likely being set up when we had those fantastic pasture growth rates in April and May (over 40kg DM/day on some of the B+LNZ monitoring sites).
There are lots of things we don't know for sure about the factors that trigger a ‘bearing season' but one aspect that was confirmed in the big 2000/2001 bearing study by Richard Hilson and co. was bodyweight gain in the first trimester of pregnancy.
Sure - we want ewes to be in good order and/or gaining some weight coming into mating and through the first cycle, but from then until scanning it seems important that body condition does not continue to pile on. The study above concluded that it was probably beneficial (from a bearing perspective) for ewes to actually lose 1-2kg liveweight once most pregnancies are established; for healthy MA ewe mobs, this period starts at the end of the first cycle.
In many a Manawatu autumn this happens by default as dictated by feed conditions and a need to preserve covers going into winter. But with the pre-winter pasture growth rates we had this year, many flocks were fed to luxury levels just at the time when this was most likely to set them up for bearings.
This is probably a tough call; on many farms this year, a lot of ewe flocks were still in quite light condition coming into mating in April, and arguably still needed to be gaining weight through into May and June for other reasons.
But remembering this year as a lesson, when faced with another growthy late autumn in the future, some energy spent managing intakes of the ewe flock to somewhere near maintenance could save headaches later on. And arguably set up a better pre-winter average pasture cover to make winter easier and spring start a bit earlier!
