Consequences of Differing Wool Growth Rates on Staple Strength of Merino Wethers with Divergent Staple StrengthsAn experiment was conducted to determine the effects of dietary protein intake after a period of weight loss on the wool components of staple strength for sheep with a history of low or high staple strength (18.0 vs 34 Nlktex). After being fed to lose 15% of their liveweight over 10 weeks, sheep within each staple strength group were assigned in equal numbers to either a low or high protein diet designed to re-gain initial liveweight in 8 weeks. Liveweight, feed intakes and the growth, fibre diameter and fibre length characteristics of wool were measured at regular intervals. After the weight loss and growth regimes were imposed there was no difference in staple strength between the low and high staple strength groups (14.4 and 14.9 Nt ktex, respectively). However, coefficient of variation (CV) of fibre diameter remained significantly different between staple strength groups. Wool growth rate at the time of diet change was the only significant component of wool growth and fibre measurements that was significantly correlated with staple strength. Supplying a high protein diet after a period of weight loss increased wool growth. This changed the position of break along the staple and increased the fibre diameter at the point of break from 13.0 to 13.9 J.1m without affecting staple strength. It also increased fibre diameter and mean fibre length growth rate. The low staple strength group had a significantly higher CV of fibre length than the high staple strength group. Fibre length growth rate to fibre diameter ratio was stable over time in the high staple strength phenotype but declined with time in the low staple strength line. The results suggest that large weight losses will reduce the difference in staple strength between animals with a history of large difference in staple strength. Rate of wool growth after the point of break did not influence this staple strength outcome.
- On completion of this topic you should be able to: • demonstrate an understanding of fibre diameter and the economic importance of fibre diameter • explain and calculate the difference between the standard deviation of diameter and the coefficient of variation of diameter • define the relationship between mean diameter, diameter variation and “coarse edge” or “prickle” • measure staple strength and describe its economic importance • explain the sources of variation in staple strength within a mob of sheep • describe localised vs generalised fibre weakness as determinants of staple strength • define and quantify the relationship between staple strength and each of minimum diameter, along-staple diameter variation, rate of change in diameter, fibre length variation and intrinsic fibre strength • relate raw wool style including the main component traits to economic importance • explain the influence of fibre diameter and fibre crimp on wool handle • describe fibre curvature and the value of curvature
- The commercial value of unprocessed wool is determined by its intrinsic quality; an indication of capacity to meet both processor and consumer demands. Wool quality is evaluated through routine assessment of characteristics that include mean fibre diameter, coefficient of variation, staple characteristics, comfort factor, spinning fineness, fibre curvature and clean fleece yield. The association between these characteristics with wool quality stems from their correlation with raw wool processing performance in terms of speed, durability, ultimate use as apparel or carpet wool, and consumer satisfaction with the end-product. An evaluation of these characteristics allows wool quality to be objectively quantified prior to purchase and processing. The primary objective of this review was to define and explore these aforementioned key wool characteristics, focusing on their impact on quality, desirable parameters and methodology behind their quantification. An in-depth review of relevant published literature on these wool characteristics in sheep is presented.
- Two experiments were conducted to examine the variation in fibre diameter profile (FDP) characteristics between staples. The mean values of all the FDP characteristics were not significantly (P > 0.05) different between staples prepared using the same and different staple preparation techniques. The residual correlation coefficient’s between staples prepared using the same staple preparation technique for all FDP characteristics ranged from r = 0.60 to 0.96. The correlation coefficients between staples prepared using different staple preparation techniques ranged from r = 0.37 to 0.97. These results indicate that it may not be sufficient to segment a single staple for estimation of certain FDP characteristics to examine differences between individual animals. One staple is sufficient to estimate the average FDP of a group of animals. FDPs generated using different staple preparation techniques can be accurately compared for most FDP characteristics.
- Fibrous fur or fleece coats have an important role in insulating animals and aiding in the maintenance of homeothermy. Alpacas, raised for fibre production, are selected towards the finest fibre to improve the wearability of their fibre in garment form. The thermal consequences of reducing the fibre diameter on the external insulation are unknown, and may have a negative effect for the alpaca's thermal balance. We hypothesised that for a given fibre density, finer fibres would trap more air and provide lower thermal conductivity when exposed to low wind speed, but would be less robust, and so provide less insulation, when exposed to higher wind speed, than thicker fibres. We measured the thermal conductance of eight pelts of similar fibre density but with varying fibre diameter at 0, 1, 2, 4 and 6 m/s wind speeds. Thermal conductivity was similar between pelts of different fibre diameters (P = 0.58) at low wind speed. Conductance increased more in pelts with finer fibres at the high wind speed than in pelts with thicker fibres (P = 0.02). Thus at the same fibre density, finer fibres result in increased heat loss at high wind speed. Increased heat loss at higher wind speed would result in the animal requiring more energy to maintain heat balance below the lower critical temperature, which will reduce fibre production efficiency.