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"On-off grazing" for Suckler Cows

Mark McGee and Nigel Gould, Teagasc, Grange Beef Research Centre, Dunsany, Co. Meath Extending the grazing season via earlier turnout to pasture in spring can lead to greater profitability in grassbased suckler beef systems by reducing slurry handling and feed costs. However, earlier turnout to pasture is not easily achievable under adverse weather and soil conditions. Previous research at Grange showed that allowing yearling cattle restricted access time to grazed pasture daily was an alternative strategy that may be applicable in poor grazing circumstances. Therefore, two experiments were carried out at Grange in 2009 to determine the effect of early turnout to pasture in spring via restricted access time daily ("on-off grazing") on the performance of lactating autumn- (Experiment 1) and spring- (Experiment 2) calving suckler cows and their calves. In Experiment 1, lactating, autumn-calving suckler cows were offered either (i) grass silage ad libitum plus 2 kg of concentrate daily or (ii) 20% of estimated total grass silage intake plus 6 hours access to pasture daily. Calves remained indoors, separated from the cows, and were offered grass silage ad libitum and had twice-daily access to their dams for suckling. The dietary treatments lasted 4 weeks, from 3rd March until 1st April. Similarly, in Experiment 2, lactating, spring-calving suckler cows were allocated to one of two diets: i) grass silage ad libitum or ii) 20% of estimated total grass silage intake plus 6 hours access to pasture daily. Calves remained indoors, separated from the cows and had twice-daily suckling access. In this case, the duration of the dietary treatments was 3 weeks, from 26th March until 16th April. In both experiments, cows that were turned out to pasture early were given a fresh allowance of grass each day, using an electric fence. All cows received a mineral/vitamin supplement spread on the silage daily, while those on the "on-off grazing" treatments also received 60 g/head/day of Cal Mag (spread on the silage) to prevent grass tetany. At the end of both experiments all animals were turned out to pasture full time until weaning. Cows and calves adapted to the daily routine within a few days. In Experiment 1, live weight gain to ~10 days after turnout was greater, BCS gain to turnout was lower (0.2 units on 5 point scale) and milk yield was higher in cows turned out early than those turned out late (Table 1). During the dietary experimental period, calves of autumn-calved cows turned out early had significantly higher average daily gain (ADG) but ADG to weaning did not differ between dietary treatments. In Experiment 2, cow live weight and body condition score was similar between both treatments. Calves of spring-calved cows turned out early had higher ADG to turnout, but subsequent ADG did not differ between dietary treatments (Table 1). In summary, there were no noticeable adverse effects on cow performance from restricted access time to grazing in early spring. The superior growth observed in calves from cows turned out early was mostly a shortterm gain. This finding is consistent with our previous research, where the additional growth benefits observed in yearling cattle turned out to pasture early is largely offset by compensatory growth in animals turned out later. Nevertheless, in the diet of the autumn-calving cows, ~80% of the daily grass silage intake plus all of the concentrate allowance was replaced with cheaper grazed grass. Similarly, for the spring-calving cows, most of the daily grass silage intake was replaced with cheaper grazed grass. There are also additional cost savings from earlier turnout in relation to slurry spreading. In conclusion, results suggest that allowing suckler cows restricted access time to grazed pasture daily is a strategy to permit early-spring grazing and consequently, to reduce costs. Table 1: Performance of autumn- and spring-calving cows and growth of their calves Exp. 1: Autumn-calving Exp. 2: Spring-calving Turnout to pasture Early Late Sig. Early Late Sig. Cow Initial live weight (kg) 623 632 NS 560 565 NS Change to turnout -36.6 -30.5 NS -3.2 -3.8 NS Change to ~10 days after turnout 18.7 1.0 ** 4.1 -7.0 NS Change to weaning 33.6 19.9 NS 32.9 11.0 NS Milk yield (kg/day) 9.4 7.5 * Calf Initial weight (kg) 200 199 NS 62 65 NS ADG to turnout (kg) 0.98 0.85 * 1.14 0.90 * ADG to ~10 days after turnout (kg) 1.14 0.92 *** 0.85 0.82 NS ADG after turnout to weaning (kg) 1.18 1.21 NS 1.04 1.10 NS ADG to weaning (kg) 1.16 1.12 NS 1.01 1.06 NS

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Microsoft Word - 52F4115C