Reproductive performance from feeding tree fodder to ewes grazing drought pasture during mating

Abstract

Grazing experiments were conducted in late summer/autumn of 2001 and 2002, at Massey University's Riverside Farm, Masterton, to determine the effects of poplar and willow supplementation during drought on ewe reproductive rate, when grazing low quality drought pasture. Ewes (55-57 kg live weight) grazed drought pasture in a rotational grazing system, with pre- and post-grazing pasture masses of 1040- 940 and 530-550 kg dry matter (DM)/ha. In 2001, poplar trimmings were offered at the rate of 1.50 and 0.75 kg/ewe/day (fresh), to the high and low treatment groups, respectively (n=100 ewes/group). In 2002, 1.40 kg/head/day (fresh) willow and poplar trimmings were offered to the willow or poplar treatment groups (n=95 ewes/group). The poplar trimmings offered to ewes in the 2002 experiment were severely contaminated by poplar leaf rust. Poplar and willow consumed was higher in mean nitrogen content and organic matter digestibility, and lower in average neutral detergent fibre content, than the low quality drought pasture consumed by the control ewes. Control ewes lost live weight (82 and 104 g/day) during the mating periods in both experiments. Supplementation with poplar and willow slightly reduced live weight loss and loss of body condition, however these differences disappeared in the post-treatment period. Reproductive rate was low in the control groups of ewes (121 & 131 lambs born/ 100 ewes mated). In the 2001 experiment, poplar supplementation increased ewe reproductive rate by 20% units (p