Productivity and Grazing Behavior of Ewes with Single or Twin Lambs Raised in Mixed Italian Ryegrass/White Clover Pasture in Southern Brazil

Abstract

The aim of this study was to compare the area production and grazing behavior of single- and twin-rearing ewes kept on a mixed Italian ryegrass/white clover pasture. The herbage allowance was maintained at 12 kg DM/100kg live weight during the experiment, by continuous variable stocking management for 112 days (4 periods of 28 days). W e measure the live weight gains, the area production and the body condition score of ewes and lambs. Animal behavior was observed on four occasions during which we evaluated whether the lambs were grazing near to or far from their mother. Live-weight output from the ewes and lambs, and net output (ewes and lambs) were calculated. Results showed that being irrespective of birth type, ewes had similar mean daily weight gains, although ewes with twin lambs presented a mean lower body condition score. Ewes live weight output/ha did not differ significantly among birth types, but twin lambs produced 98.2 kg (45%) more live weight gain/ha. Total net live-weight output (ewes + lambs) was 121.5 kg greater for twins than for singles. Ewes with twin lambs spent more time grazing and ruminating. Lambs increased the time they spent grazing in each successive period. Single lambs spent significantly longer time grazing within 12 m of their dams (near grazing). Analysis of far grazing times by the broken line method showed that growing lambs rapidly increase the time spent far grazing up to a live weight of 20.3 kg in both birth types, which occurs at 95.3 and 115.9 days of age for single and twins, respectively. The results indicate that twin lambs are more productive than singles, when evaluated per area unit of pasture.