Pasture systems to improve productivity of sheep in south-western Victoria 2. Animal production from ewes and lambs

Abstract

Two pasture systems (Typical, Upgraded) were compared at five on-farm sites across south-western Victoria between 1990 and 1996. The Typical pasture treatment mimicked the pastures common in the region, with volunteer annual-based species fertilised with ~5 kg/ha.year phosphorus (P). The Upgraded pasture treatment was sown to phalaris, perennial ryegrass and subterranean clover using cultivars recommended for the particular area. Higher rates of fertiliser (13–25 kg/ha.year P) plus other nutrients were applied. Both pastures were set-stocked with breeding ewes. The stocking rate on the Typical treatments was based on normal farm practice. Initially, the stocking rate of the Upgraded pastures was 15% higher than the Typical pastures and increased over time depending if the ewes in the Upgraded pastures were heavier than those in the Typical pastures. Measurements included pasture growth, composition and persistence, ewe stocking rates, ewe and lamb liveweights and condition scores, lambing, marking and weaning percentages, fleece characteristics and supplementary feeding. Over the 6 years, the average carrying capacity of the Upgraded pastures was 18.0 DSE (Dry Sheep Equivalents)/ha compared with 10.2 DSE/ha on the Typical pastures (P < 0.001). As well, the ewes on the Upgraded pastures were 2–3 kg heavier (P < 0.001) and 0.3 condition score higher (P < 0.001) than those on the Typical pastures. Ewes grazing the Upgraded pastures cut significantly more wool per head (4.8 versus 4.5 kg) of higher micron wool (23.1 versus 22.6 um, P < 0.001) but with similar yield and strength. There was no difference in the supplementary feeding required on the treatments. Ewes grazing Upgraded pastures had significantly higher lambing (116 versus 102%), marking (86 versus 81%) and weaning percentages (84 versus 79%) and weaned significantly heavier lambs (23.6 versus 22.6 kg) than those on Typical pastures. There was less feed on offer (P < 0.05) in the Upgraded pastures compared with the Typical pastures in autumn–winter but similar or higher levels in spring and summer. Gross margins using current costs and prices were $20 and $24/DSE for the Typical and Upgraded pastures, respectively. These values were used in a discounted cash flow analysis to determine the long-term benefits of the treatments. Assuming a 12-year life for the pasture, the internal rate of return was 27% with the breakeven point in Year 7. Treatment and ewe condition score significantly influenced lambing percentage with ewes in condition score 3.0 at joining having a lambing percentage of 111% compared with 95% if at condition score 2.3. Irrespective of condition score, ewes grazing Upgraded pastures had a 7% higher lambing percentage than those grazing the Typical pastures. Ewe condition score and lambing time significantly affected weaning weight. Lambs born to ewes in condition score 2.3 during pregnancy and lambing in autumn, reached only 32% of mature ewe liveweight at weaning whereas lambs from ewes at condition score 3.0 achieved 51% of mature weight by weaning.

Review of sheep body condition score in relation to production characteristics

“…The end point from a reproductive perspective for farmers is often the numbers of lambs weaned per ewe presented for breeding. Kleemann et al (2006) in an across-flock analysis with Merino ewes, Newton et al (1980) with Masham ewes, and Saul et al (2011) with Merino ewes all reported that BCS at breeding and/or mid-pregnancy was positively correlated with the number of lambs weaned per ewe exposed to the ram. Vatankhah et al (2012), with Lori-Bakhtiari ewes, reported that BCS at breeding had a positive effect on the number of lambs weaned per ewe, but only to a BCS of 3.0 before it plateaued.…”

Improving the nutrition of Merino ewes during pregnancy increases the fleece weight and reduces the fibre diameter of their progeny's wool during their lifetime and these effects can be predicted from the ewe's liveweight profile

“…site or 33 months of age at the WA site, depending on whether the maternal environment was defined as the nutritional treatments, the liveweight profile of individual dams or the birth and rear type of the progeny themselves. Nevertheless, the cumulative difference between the extreme nutritional treatments that covered the range typical of those experienced by many Merino ewes during pregnancy and lactation on commercial farms across southern Australia (Kelly 1992;Kleemann and Walker 2005;Saul et al 2011), was~1.1 kg of clean wool and 0.2 mm over five shearings at the Vic. site and 0.8 kg of clean wool over three shearings at the WA site.…”

Effects of three whole-farmlet management systems on Merino ewe fat scores and reproduction

“…According to Saul et al (2011), a trial in south-western Victoria over 6 years showed that grazing systems with upgraded pastures resulted in a 75% increase in stocking rate, a higher condition score by 0.3, 13% more lambs born and 6% more lambs marked and weaned, all without any increase in the level of supplementary feed required. Therefore, it could be expected that the farmlets might also differ in reproductive efficiency; given the fat scores were below target (score of 3), reproductive performance is likely to have been below the potential for fine wool (16 m) ewes.…”