The wool production and reproduction of Merino ewes can be predicted from changes in liveweight during pregnancy and lactation

Abstract

Abstract. Defining the nature of the relationship between change in liveweight throughout a breeding cycle and ewe wool production and reproduction would be useful for developing management guidelines for Merino ewes. In this paper we tested the hypotheses that (1) feed on offer has variable effects on liveweight profiles of individual ewes; and (2) liveweight profiles of individual ewes can be used to predict their fleece wool production and reproductive performance. At sites in Victoria and Western Australia in 2001 and 2002, pregnant Merino ewes were exposed to 10 nutritional treatments. In each of the four experiments, ewes in average condition score 3 at artificial insemination were fed to achieve either maintenance or loss of a condition score over the first 100 days of pregnancy before grazing one of five levels of feed on offer between Day 100 and lamb weaning. Across all four experiments, the average difference in ewe liveweight between extreme treatments was: 7.0 kg (range 4.7-8.7 kg) at Day 100 of pregnancy; 11.9 kg (range 4.9-17.8 kg) at lambing; and by weaning was 13.9 kg (range 8.8-22.7 kg). Liveweight at joining and liveweight change during pregnancy and lactation of individual Merino ewes were significantly related to their clean fleece weight, fibre diameter and staple length and thus the second hypothesis was supported. Heavier ewes at joining produced more wool that was longer and broader and this effect was consistent across both sites and years. A 10-kg loss in ewe liveweight between joining and mid pregnancy, mid pregnancy and lambing or during lactation reduced clean fleece weight by 0.4-0.7 kg and fibre diameter by 0.5-1.4 um. At the Victorian site, where ewes were shorn in summer, a loss of 10 kg in liveweight between joining and Day 100 of pregnancy reduced staple strength by 5 N/ktex. As expected the influence of food on offer on changes in ewe liveweight was different between years and sites and between late pregnancy and lactation due to a complex group of pasture and animal factors. Therefore, managing changes in ewe liveweight itself rather than feed on offer will achieve more predictable outcomes. A higher liveweight at joining resulted in a predictable improvement in ewe reproductive rate and liveweight at joining was more important than the liveweight profile leading up to joining. This paper has shown that it is possible to predict the differences in wool production and reproductive rate of flocks of Merino ewes if ewe liveweight records at key times are known.

Managing the nutrition of twin-bearing ewes during pregnancy using Lifetimewool recommendations increases production of twin lambs

“…This is possibly due to the inability for twin-bearing ewes to be able to consume enough feed to meet their energy requirements in late pregnancy and lactation. There was a 0.25-kg difference in ewe CFW between LW and NP ewe flocks, which was less than that reported for the national paddock-scale analysis (0.67 kg difference for 1 CS; Behrendt et al 2011) and the plot-scale analysis (0.61 kg difference for 10 kg; Ferguson et al 2011). The LW ewes produced wool that was 1 mm broader in fibre diameter than the NP ewes, which is similar to that predicted by the national paddock-scale analysis (0.9 mm for 1 CS difference; Behrendt et al 2011) and the plot-scale analysis (1 mm difference for 10 kg).…”

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 .…”

“…Ferguson et al (2011) and Behrendt et al (2011) describe the design of the plot-(2 sites · 3 years) and paddock-scale (15 sites) experiments, respectively. In brief, the plot-scale experiments involved up to 1500 Merino ewes at two sites in each of 3 years.…”

Follicle development, endocrine profiles and ovulation rate in adult Merino ewes: effects of early nutrition (pre- and post-natal) and supplementation with lupin grain

“…1). The 'low' group was considered to be a control, based on the predicted liveweight changes in the Merino ewes under paddock conditions (Ferguson et al 2011). So, the foetuses were exposed to maternal undernutrition around day 65 of pregnancy, when their ovaries are thought to be most sensitive to metabolic inputs .…”