• Seasonal Variation in Fibre Diameter and Length in Wool of Grazing Merino Sheep with Low or High Staple Strength

    The associations between fibre growth characteristics and wool staple strength were investigated in groups (n = 10) of Merino wethers with either low or high staple strength. Sheep grazed together on pastures based on subterranean clover and annual rye grass for about 13 months. The sheep were weighed and injected intradermally with [35 S]-cysteine at about 14-day intervals. Mid-side patches were harvested and dye bands placed in the wool at about 28-day intervals. Patch clean wool growth, pasture digestible dry matter/ha and pasture crude protein/ha had similar seasonal amplitudes of production (287, 286 and 267% of respective minimum). These were significantly higher than the seasonal amplitude in liveweight (24.5%). The seasonal amplitude in fibre diameter was significantly greater than that for rate of fibre elongation (71.4 and 41.4% respectively). This seasonality in fibre length and diameter resulted in statistically significant seasonal fluctuations in the ratio of fibre length growth to fibre diameter. Fortnightly variability in fibre diameter was not significantly related to variability in fibre length growth rate between sheep for individual time periods. However, for the pooled data over the experimental period a statistically significant relationship (R2 = 0.13, P < 0.01) was improved with the addition of parameters for sampling time and staple strength group. Staple strengths for the low and high staple strength groups were 25.6 and 32.8 N/ktex respectively (P = 0.057). There were no significant differences between the staple strength groups in seasonal change in liveweight, wool production or fibre parameters measured in this study but the low staple strength group had longer fibres. Staple strength was most highly correlated with mid-side fibre diameter coefficient of variation (R2 = 0.50) followed by seasonal amplitude in liveweight. more »
  • Do Price Premiums for Wool Characteristics Vary for Different End Products, processing Routes and Fibre Diameter Categories?

    No Australian wool price hedonic studies have separated auction data into different end product-processing groups (PPR) on the basis of all fibre attributes that affect the suitability of wool sale lots for PPR. This study was conducted to assess: (1) whether including information about PPR groupings is more useful in understanding price than clustering by broad fibre diameter (FD) categories, and (2) if the ‘noise’ of macroeconomic effects on price can be reduced by using a clean price relative to the market indicator (RelPrice) formula or a log RelPrice formula compared with log price or clean price. Hedonic models using data derived from 369 918 Australian auction sale lots in 2010–2011 were estimated for these four dependent price variables. Linear FD models predicted less of price’s variance than quadratic or exponential models. Segmenting wool sale lots into 10 PPR before wool price analyses was found to increase the proportion of price variance explained and thus be worthwhile. The change in price with a change in FD, staple length and staple strength differs significantly between PPR. Calculating RelPrice or log RelPrice appears a better price parameter than clean price or log price. Comparing the RelPrice and clean price models, the mean absolute percentage errors were 6.3% and 16.2%, respectively. The differences in price sensitivity to FD, staple length and staple strength across PPR implies a complex set of price-setting mechanisms for wool as different users place different values on these wool properties. These price-setting mechanisms need to be incorporated in hedonic models for agricultural products that possess this characteristic. The wool price premiums can be used to estimate relative economic values when constructing sheep breeding selection indexes and can help determine the most profitable wool clip preparation strategies. more »
  • Undegradable Dietary Protein in Alpaca Diets Affects Fibre Diameter and Time Spent Urinating

    There is evidence that alpacas derive most of their glucose for energy from the deamination of amino acids. Consequently, they may have an insufficient supply of amino acids to meet their requirements for fibre growth. To optimise fibre production, it may be necessary to supply alpacas with supplemental protein to meet their requirement for extra amino acids. In this study, we examined if the proportion of rumen-degradable dietary protein (RDP) to undegradable dietary protein (UDP) from canola meal influenced the fibre growth of alpacas. We hypothesised that alpacas fed at maintenance a diet containing canola meal protein high in UDP would produce more fibre and spend less time urinating than peers fed a similar amount of canola meal protein with a low proportion of UDP. Four groups of eight alpacas were fed diets with the following ratios of UDP : RDP: 0 : 100, 30 : 70, 60 : 40 or 100 : 0 from canola meal protein. The fibre growth of the animals was measured over 2 months and the behaviour of the animals in the two extreme groups (0 and 100% UDP) was measured over 5 days. The alpacas fed the 0% UDP diet produced fibre of finer diameter than the alpacas fed diets containing higher levels of UDP (P = 0.039) and the 0% UDP group also spent more time urinating (P = 0.027). This result suggests that alpacas may have a limited ability to recycle nitrogen to the fermentative chambers of their stomach when fed a diet low in UDP. Consequently, microbial protein synthesis in the fermentative chambers may have limited the supply of amino acids available to the alpacas. more »