The effects of allowance and frequency of allocation of deferred herbage, and grass silage feed value, when offered to ewes in mid-gestation on ewe and lamb performance and subsequent herbage yield

Abstract

The effects of (i) herbage allowance, (ii) frequency of allocation and (iii) grass silage feed value on ewe and lamb performance were studied in mid-gestation ewes. Furthermore, the effects of (i) herbage allowance, (ii) frequency of allocation and (iii) grazing date and their interactions on subsequent herbage yield and feed value were also evaluated. Swards, which had a cut of silage removed on 6 September, received fertiliser nitrogen (34 kg/ha) for extended (deferred) grazing between 6 December and 1 February. Two grass silages differing in feed value were ensiled either precision chopped or in big bales from predominantly perennial ryegrass swards, respectively. In experiment 1, a completely randomised study involving 120 crossbred mid-gestation ewes (Belclare 3 Scottish Blackface) that had been mated in October was undertaken to evaluate the effects of extended grazed herbage allowance (1.0 and 1.8 kg dry matter (DM)/day), frequency of herbage allocation (daily and twice weekly) and grass silage feed value (low and medium) on ewe and subsequent lamb performance. The six diets were offered from days 63 to 120 of gestation. From day 120 of gestation to parturition all ewes were housed and offered the medium feed value silage ad libitum. All ewes received 19 kg concentrate prior to lambing. Increasing herbage allowance increased forage intake ( P , 0.05), lamb birth weight ( P , 0.01), weaning weight ( P , 0.05) and growth rate from birth to weaning ( P , 0.05), decreased herbage utilisation ( P , 0.05) and tended to increase ewe condition score at lambing ( P 5 0.06). Frequency of herbage allocation or grass silage feed value did not alter ( P . 0.05) ewe or subsequent lamb performance. In experiment 2, the effect of extended grazed herbage allowance (1.0 and 1.8 kg DM/ewe daily), frequency of allocation (daily and twice weekly) and grazing date (6 to 12 December, 27 December to 3 January and 17 to 23 January) on herbage yield at two harvest dates (27 April and 25 May) was examined in a split plot design study consisting of 72 plots. Delaying grazing date decreased herbage yield ( P , 0.01) whilst delaying harvest date increased herbage yield ( P , 0.05). Frequency of herbage allocation did not alter ( P . 0.05) subsequent herbage yield. It is concluded that for ewes in mid-gestation 1.0 kg of low feed value silage DM had the same feed value, as determined by weaned lamb weight, as 1.3 kg herbage DM allowance. Each 1-day delay in grazing date reduced herbage DM yield by 54.2 kg/ha.

Potential Use of Tropical Grass for Deferment in Semi-Arid Region

“…This structural characteristic of massai guineagrass followed the same trend of the leaf component (Figures 1(C) and (D)), which is more important than the stem. The relative diminution of the availability of leaves affects the animal intake and consequently its performance [13] [14].…”

The effects of allowance of deferred herbage and concentrate supplementation when offered to ewe lambs, and system of allocation when offered to ewes in late gestation, on animal performance

“…During extended grazing, allocation of herbage, by erecting and moving fences, is labour demanding and currently labour is an expensive commodity on many sheep farms. Previous studies at this centre (Keady and Hanrahan, 2009b,c) have shown that allocating herbage either daily or twice weekly did not alter animal performance or subsequent herbage growth.…”

“…Previous studies at this centre have shown that providing extended (deferred, winter) grazing for ewes in mid (Flanagan, 2003; Keady et al. , 2007; Keady and Hanrahan, 2009b), late (Keady et al. , 2007) or throughout (Keady et al.…”

“…Herbage yield and allowance, and concentrate supplementation, are the major factors that determine stock‐carrying capacity during extended grazing. While the impact of AEGH to ewes during mid and late pregnancy on ewe and subsequent lamb performance have been evaluated in previous studies (Keady and Hanrahan, 2009a,b,c), there is a paucity of data on the effects of herbage allowance on the performance of ewe lambs.…”

“…Chemical composition of the herbage and concentrate was as described by Keady et al. (1998, 1999) and Keady and Hanrahan (2009b).…”