Pasture Can Compensate02 July 2013
Pushing feed into stores over winter has no benefits as liveweight gain shoots up when the summer grass arrives and cattle are turned out to pasture, say Edward O'Riordan, Mark McGee and Declan Marren of Teagasc.
For economic reasons, exploiting compensatory growth is a key goal when feeding weanling/store cattle in winter. Research at Teagasc Grange has determined that the optimum winter growth rate for steers and heifers destined to return to pasture for a second grazing season is in the region of 0.4 to 0.7kg liveweight/day, if they are to optimise compensatory growth on cheaper produced grass. In other words, there was no point in over-feeding weanlings in winter as, during the subsequent grazing season, cattle that gained less over the winter had the highest liveweight gain at pasture. This ability of “restricted” animals to subsequently compensate at pasture meant that at least two-thirds of the winter weight advantage, due to higher levels of supplementation, had disappeared by the end of grazing season. However, unlike steer (or heifer) systems, the optimal growth rate during the first winter for high growth potential young suckler bulls to exploit subsequent compensatory growth at pasture is not clear.
To determine this, a study was recently undertaken at Grange. Spring-born sucker bulls were offered grass silage to appetite and this was supplemented with either 2, 4 or 6kg concentrate/head/day to achieve winter liveweight gains ranging from 0.6 to 1.2kg/day. At the end of the winter, bulls supplemented with 4 and 6kg of concentrate daily were 30 and 63kg heavier, respectively, than bulls supplemented with 2kg of concentrate daily. However, after approximately 100 days at pasture, the weight difference between the 2 and 4kg concentrate winter supplemented groups had disappeared, and the weight difference between the 2 and 6kg supplemented groups had diminished to 21kg live weight. Thus, based on liveweight differences evident at the end of the winter, it may be inferred that it “paid” to feed the extra concentrate to get higher winter growth rates. However, based on liveweight differences following three months at pasture, a totally different conclusion can be drawn. These findings for bulls are consistent with earlier results for steers.