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.

The effect of chemical compounds on the palatability of a wheaten hay was investigated in short-term preference tests in which sheep were offered simultaneously treated and untreated hay. The palatability of wheaten hay chopped to 17 mm lengths was increased by treating it with aqueous solutions of either butyric acid (range 1.3-10 g/kg air-dry hay) or monosodium glutamate (2.4-44 g/kg hay). Hay chopped to 17 mm lengths was chosen because its potential intake rate was sufficiently low to allow the best quantitative measure of the increase in palatability to be established. The palatability of the same hay chopped to 6 mm lengths was decreased by applying MgO powder (1.6-60 g/kg hay) to hay pretreated with a solution of (1% w/w) sodium caseinate to adhere the MgO. The palatability of 6 mm hay was also decreased by treating it with aqueous solutions of acetic acid (0.02-10 g/kg hay), aconitic acid (0.2-19 g/kg hay) or malonic acid (1-20 g/kg hay). Hay of 6 mm lengths was chosen because its potential intake rate was sufficiently high to allow the best quantitative measure of the decrease in palatability to be determined. From the dose response curves, it was possible to identify a single concentration of selected chemical compounds that was suitable for altering the palatability of hay. A combination of butyric acid (2.5 g/kg hay) and monosodium glutamate (10 g/kg hay) were identified as the most suitable for increasing the palatability of 17 mm hay, and MgO (41 g/kg hay) or acetic acid (5 g/kg hay) for decreasing the palatability of 6 mm hay. A quantitative measure of the effect of these chemicals on the change in the palatability of either 17 or 6 mm hay was obtained. The sheep demonstrated a strong preference for 17 mm hay treated with a combination of butyric acid plus monosodium glutamate and conversely, a strong aversion to 6 mm hay treated with MgO. The specific concentration of the compounds selected would be suitable for investigating the effect of a change in palatability on the voluntary intake of wheaten hay.

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A new technique was developed to measure the yield and mean fibre diameter of cashmere. The fibre diameter distribution of 2-mm snippets measured by the Optical Fibre Diameter Analyser (OFDA) was used to calculate cashmere yield of a goat fleece without dehairing. The total volume of fibres <35 and >35 �m was then calculated from the diameter distribution, and from this it was possible to predict the cashmere yield of 6 standards ranging from 10 to 60% yield (r2 = 0.98, n = 30). In addition, the Shirley Analyser was compared with the OFDA technique for measuring cashmere yield (r2 = 0.59, n = 110). OFDA estimates of cashmere yield were on average 10% higher (standard deviation � 7%) than those of the Shirley Analyser, indicating poor agreement between the 2 techniques. This is likely to be due to the Shirley Analyser and OFDA estimates of cashmere yield being affected by different fibre properties of the fleeces. There was good agreement between the Fibre Diameter Analyser (FDA) and the OFDA for measuring mean fibre diameter (MFD) of dehaired cashmere samples (r2 = 0.97, n = 108). There was also a good agreement in estimates of cashmere MFD between whole fleece and dehaired cashmere samples measured by the OFDA (r2 = 0.97, n = 77). Calculation of cashmere yield and down MFD by the OFDA has shown it to be accurate for measuring standard samples, and as precise as the Shirley Analyser. Therefore, the use of the OFDA is a potential low cost alternative to rank the value of cashmere goats for breeding.

SUMMARYThe relationships between organic-matter digestibility (OMD), dry-matter intake (DMI) and the mean retention time (MRT) of unabsorbed solutes in the gastrointestinal tract were examined using six fistulated, cross-bred, castrate male sheep. Measurements were made on each sheep at two different DMIs within the range 28–81 g D.m./(day. kg0·75). There were negative, curvilinear relationships between MRTs (both rumen and total) and DMI and positive, curvilinear relationships between OMD and MRTs. As a consequence, there was a negative, rectilinear relationship between OMD and DMI. OMD declined by 0·022 when DMI increased from calculated maintenance to twice maintenance. The proportion of the total MRT accounted for by rumen MRT did not change significantly; the mean value was 0·364 ( ± S.e. 0·010).