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

Abstract

Abstract. Nutrition of ewes during pregnancy can have permanent impacts on the production potential of their progeny. The hypothesis tested in the experiments reported in this paper was that improving the nutrition of Merino ewes during pregnancy and lactation increases the fleece weight and reduces the fibre diameter of their progeny's wool during their lifetime. In addition, that these effects on the progeny's wool production can be predicted from the ewe's liveweight profile. At sites in Victoria and Western Australia in each of 2 years, a wide range in the liveweight and condition score profiles of Merino ewes was generated by varying the amount of supplements fed from joining to Day 100 of pregnancy and the amount of feed on offer grazed from Day 100 to weaning. The site in Victoria was based on perennial pastures and included both single-and twin-bearing ewes whereas the site in Western Australia was based on annual pastures and included singlebearing ewes only. The production and characteristics of wool from the progeny were measured until 51 months of age at the site in Victoria and 33 months of age at the site in Western Australia. The nutritional treatments and the resulting changes in ewe liveweight had significant impacts on the fleece weight and to a lesser extent the fibre diameter of wool produced by their progeny, but there were no consistent effects on other characteristics of progeny fleece wool. The fleece weight of the progeny was related to the liveweight change during pregnancy of their mothers (P < 0.05) and the relationships were similar for the two experiments at each site. At the site in Victoria, a loss of 10 kg in ewe liveweight between joining and Day 100 of pregnancy reduced fleece weight by~0.2 kg at each shearing until 51 months of age whereas gaining 10 kg from Day 100 of pregnancy to lambing had the opposite effect. The effect of changes in ewe liveweight during late pregnancy on the fleece weight of their progeny at each shearing was of similar magnitude at the site in Western Australia. When evident, the effect of the ewe liveweight profile on the fibre diameter of progeny wool was opposite to the effect on clean fleece weight and the effect of poor nutrition in early to mid pregnancy could be completely overcome by improving nutrition during late pregnancy. Twin-born and reared progeny produced~0.3 kg less clean wool at each shearing (P < 0.001) that was 0.3-mm broader (P < 0.001) than that from single-born progeny at the site in Victoria. However, the effects of varying ewe nutrition and ewe liveweight change during pregnancy on fleece weight and fibre diameter of progeny wool were similar (P > 0.05) for both single-and twin-born or reared progeny. Overall, these results supported our hypothesis and it is clear that the nutritional management of Merino ewes during pregnancy is important for optimal wool production from their progeny during their lifetime.

The merit of condition score and fat score as alternatives to liveweight for managing the nutrition of ewes

“…We therefore reject this component of our hypothesis and suggest that 0.19 be adopted as the standard multiplier for calculating the relationship between Tissue depth at the GR site (mm) Eye muscle depth at the C site (mm) standard reference weight and condition score. Ewe and progeny production responses from the Hamilton plot-scale site, reported by Ferguson et al (2011 and Thompson et al (2011aThompson et al ( , 2011b, were used to establish ewe liveweight profiles to maximise profit and welfare outcomes for different regions and times of lambing . As the average ratio of change in liveweight to change in condition score in this data was 10 (Table 1, Hamilton, 2001 and2002) this conversion factor was used when the guidelines were converted from liveweight to condition score profiles .…”

“…Liveweight profile of Merino ewes is related to production of the ewe ) and her progeny Thompson et al 2011aThompson et al , 2011b and the profitability of the sheep enterprise . Surveys show that few farmers routinely weigh ewes to manage their nutrition as they believe this practice has little value, is time consuming and/or expensive (Jones et al 2011).…”

Whole-farm profit and the optimum maternal liveweight profile of Merino ewe flocks lambing in winter and spring are influenced by the effects of ewe nutrition on the progeny's survival and lifetime wool production

“…site reported by Oldham et al (2011) and Thompson et al (2011a), see Table 5. The calculation for the variation in survival had a further adjustment applied because the impact of ewe nutrition on progeny survival was greater in the paddockscale experiments than the plot-scale experiments .…”

“…The adjustment factors for Great Southern WA and southern NSW were 8.5 for singles and 2.0 for twins, whereas these adjustment factors were double these values for south-west Vic. The impacts of the adjustments are shown in Tables 6-8. The adjustment in progeny wool production was based on hogget data and applied to all age groups of progeny because the weight of evidence supports that the progeny effects are permanent (Kelly et al 1996(Kelly et al , 2006Thompson et al 2011a). The production of the ewe component of the flock was also adjusted, because those animals are the progeny of the ewes from the previous generation, and it is assumed that the nutrition strategy for the ewes has been applied and the flock has achieved a steady state.…”

“…However, this work only considered extreme nutritional regimes and did not attempt to identify an optimal liveweight profile. The Lifetimewool project has shown that the liveweight profile of Merino ewes can reliably predict the production of ewes and their progeny Thompson et al 2011a). This new information provides the necessary production responses required to develop optimum liveweight profiles for ewe flocks in different regions and lambing at different times.…”