In ewe lambs, acceleration of growth and accumulation of both muscle and fat leads to earlier sexual maturity and better reproductive performance. The next stage in the development of this theme is to test whether these aspects of growth in young ewes affect milk production in their first lactation and the growth of their first progeny. We studied 75 young Merino ewes that had known phenotypic values for depth of eye muscle (EMD) and fat (FAT), and known Australian Sheep Breeding Values for post-weaning weight (PWT) and depths of eye muscle (PEMD) and fat (PFAT). They lambed for the first time at 1 year of age. Their lambs were weighed weekly from birth to weaning at 10 weeks to determine live weight gain and weaning weight. Progeny birth weight was positively associated with live weight gain and weaning weight (P0.05). The PWT of the sire was positively associated with live weight gain (P0.05). The concentrations of fat, protein, lactose and total solids in the milk were not affected by the phenotype or genotype of the mothers or of the sires of the mothers, or by the sex of the progeny (P>0.05). We conclude that selection of young Merino ewes for better growth, and more rapid accumulation of muscle and fat, will lead to progeny that are heavier at birth, grow faster and are heavier at weaning. Moreover, milk production and composition do not seem to be affected by the genetic merit of the mother for post-weaning live weight or PEMD or PFAT. Therefore, Merino ewes can lamb at 1 year of age without affecting the production objectives of the Merino sheep industry.

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The objective of this paper is to quantify the magnitude of the major sources of variation, which affect in vitro digestibility (DMD) and concentrations of neutral detergent fibre (NDF), acid detergent fibre (ADF), and crude protein (CP) of annual pastures in Mediterranean-type climate zones. Four experiments were conducted in the south-west of Western Australia in 2006–07 and 2007–08, where the supply of nitrogen, phosphorous, potassium, or sulfur and pasture types were varied. Effects of seasonality, fertiliser application, pasture type, and site were analysed with an auto-regression maximum likelihood procedure. Temperature sum was used to explain the seasonal differences in DMD, CP, NDF, and ADF. Seasonality explained 82, 79, 79, and 62% of the total variation in DMD, NDF, ADF, and CP, respectively, with only an additional 5, 5, 6, and 24% being explained by the combined effects of site/management, fertiliser application, and pasture type. The differences in DMD, NDF, ADF, and CP, between sites, were 2.3–6.0%, 4.6–18.7%, 5.8–8.6%, and 1.5–17.4%, respectively. Pasture types differed by 6.6–9.5%, 9.0–11.4%, 3.1–6.1%, and 5.1–5.2% for DMD, NDF, ADF, and CP, respectively. The differences between sites and pasture types were markedly larger for CP, NDF, and ADF than for DMD. Fertiliser application did not affect nutritive characteristics, with the exception of N application rates on CP. It was concluded that the seasonality model captured nearly all of the temporal variation in DMD, NDF, and ADF but not in CP. The spatial variation in DMD was mostly determined by pasture type. By comparison, NDF and ADF were most strongly affected by grazing management, and CP by the availability of N.

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