Fiber characteristics of qiviut and guard hair from wild muskoxen (Ovibos moschatus).

In response to increasing commercial interest and the high market value of qiviut (the downy underwool of the muskox), we have employed standards and measurements used in the wool and cashmere industries to describe qiviut fiber characteristics. Fleece samples (qiviut with guard hair) were shaved from the midshoulder of 299 wild muskox hides of known sex and age (1, 2, 3, and 4+ yr) during the Banks Island, Canada, muskox harvest in November 1997. Samples were analyzed for fiber diameter distribution of raw fiber and qiviut, scoured and qiviut yields, and lengths of guard hair and qiviut fiber. We found a sex x age interaction for average fiber diameter (AFD) in raw fiber (P= 0.002) and qiviut (P < 0.001) only. Adult males had significantly coarser AFD than females (21.5 microm, males vs 20.1 microm, females and 18.2 microm, males vs 17.5 microm, females) for raw fiber and qiviut, respectively. Qiviut AFD from yearlings was 1.7 microm finer than the AFD of adult qiviut. Fiber diameter distribution (SD) decreased with age in the raw sample (P < 0.003) and qiviut (P < 0.001) and qiviut SD was greater (P < 0.001) in males than in females. Qiviut theoretical yield (% mass of fibers < or = 30 microm) increased (P < 0.001) with age, and females had higher theoretical yields than males (P < 0.001). Scoured yield did not vary between sexes in any age class and averaged 93.3%. Qiviut staple length did not differ with either age or sex. In summary, differences between the sexes were small up to the 3rd yr, and these differences were not likely to be of commercial importance. However, considering that AFD is a primary commercial criterion of value, AFD changes from 16.5 microm in yearlings to 18.2 microm in adults and from 17.5 microm in adult females to 18.2 microm in adult males would be expected to result in significant differences in commercial value.

Prediction of clean mohair, fiber diameter, vegetable matter, and medullated fiber with near-infrared spectroscopy.

Four experiments were conducted in three separate years to test the utility of near-infrared spectroscopy (NIRS) to predict the clean mohair content of Angora goat fleece. Mohair fleece samples were obtained each year from yearling billies at the conclusion of the Angora Goat Performance Test conducted at the Texas A&M University Research Station, Sonora. In Exp. 1 (n = 293) and Exp. 2 (n = 256), fleeces were scanned with a Pacific Scientific (Silver Spring, MD) near-infrared spectrometer fitted with a fiber-optic probe, and calibrations were developed for clean mohair content. In Exp. 3, 59 mohair fleeces collected at the Texas A&M Research Station in San Angelo were sampled four times each. Each sample was scanned with the same spectrometer in reflectance mode fitted with a transport mechanism. This mechanism allowed the instrument to scan a 15-cm2 segment of the fleece sample. Conventional procedures to determine reference values for mohair yield, vegetable matter content, fiber diameter, and percentage of medullated and kemp fibers were conducted. Prediction equations were developed that related NIR spectra to reference values for yield and diameter parameters and were used to predict mohair characteristics for each fleece sample. The predicted and reference values were subjected to a simple analysis of variance to determine variation within and across samples. In Exp. 1, mohair base was related to NIR spectra with R2 = .46 and standard error of calibration (SEC) = 2.84%. In Exp. 2, similar repeatability errors for mohair base could be obtained for both reference- and NIRS-derived values. Fiber diameter and medullated fibers were poorly related to NIR spectra. When samples were scanned using the transport mechanism (Exp. 3), R2 and SEC were .82 and 1.19% for mohair base and .93 and .98 microm for fiber diameter, respectively. The CV for mohair base and diameter were 1.0 and 1.4%, whereas those for predicted mohair base and diameter were 1.4 and 3.4%, respectively. The increased variation within samples for predicted values represents sampling error and lack of fit between NIRS and the laboratory determined values. When the samples from Exp. 1 and 2 were rescanned with the NIRS transport (Exp. 4), R2 and SEC were .79 and 2.03% for mohair base and .52 and 3.49 microm for fiber diameter. The fiber optic probe would facilitate real-time analysis on the shearing floor, but our data indicate that the spectral limitations so far are too severe. A large sample device such as the transport gave excellent results for predicting mohair base and fiber diameter.

Measurement of medullation in wool and mohair using an Optical Fibre Diameter Analyser.

We conducted three experiments to evaluate the Optical Fibre Diameter Analyser (OFDA) for estimating medullation (med [M], kemp [K], and total [T] medullated fiber content) in mohair and wool produced by Angora goats and sheep, respectively. Medullation can be a beneficial characteristic in certain types of wool, but it is highly undesirable in mohair and apparel wools. Current techniques for evaluating medullation in animal fibers are laborious, slow, and expensive. The OFDA had been modified by the manufacturer to measure fiber opacity distribution, a characteristic known to be indicative of medullation in white fibers, and was capable of providing such measurements in a very short time. Measurements made on magnified fiber images produced with a projection microscope (PM) were used as a reference for M, K, and T in fiber samples. An initial experiment with 124 mohair samples (T = .10 to 9.10%) seemed to indicate that OFDA estimates of M, K, and T were only poorly correlated with corresponding PM values (r2 = .5409, .1401, and .5576, respectively). However, a second experiment using wool and mohair samples containing a wider range of medullation (T = .58 to 26.54%) revealed that OFDA estimates of M, K, and T for wool were highly correlated with PM measurements (r2 = .9853, .9307, and .9728, respectively). Evidence was also obtained indicating that the low r2 values associated with mohair relationships were likely due to a combination of factors: 1) high variation among the standard PM measurements and 2) the relatively low M, K, and T contents of the mohair samples compared with wool. In a third experiment, greater accuracy was obtained in the PM measurements by evaluating many more individual fibers per sample (10,000). In this case, OFDA estimates of M, K, and T for mohair were highly correlated with corresponding PM measurements (r2 = .8601, .9939, and .9696, respectively). However, the two sets of linear regression equations obtained for wool and mohair were somewhat different, indicating that separate calculations should be used to estimate PM measurements from OFDA data. In conclusion, it was demonstrated that the OFDA instrument is capable of providing relatively fast, accurate, and potentially less expensive estimates of medullated fiber characteristics in mohair and wool.

Animal performance and fleece characteristics of Angora goats maintained on western and southern Texas rangeland.

Two hundred castrated male Angora goats (18 mo of age) were divided equally between rangeland sites in the oak savannah of the Edwards Plateau (EP) and the mixed-brush shrublands of the South Texas Plains (STP) for 5 yr to study influence of environment and age on body weight (BW), mohair production, and mohair fiber characteristics. Goats were grazed on rangeland typical of the respective regions and were given typical management that included shearing in February and July or August of each year. Shorn goats were weighed and individual fleeces were measured for grease weight (GFW), clean yield (CMFP), average fiber diameter (AFD), and proportion of medullated fibers, med (MFP) and kemp (KFP). Rainfall and maximum and minimum temperatures were recorded daily at each site. The AFD (P = .01) and its associated SD (P < .001) and kemp levels (P = .03) were all higher at the STP than at the EP site (39.4 vs 37.9 microns, 10.4 vs 11.1 microns, and .80 vs .68%, respectively). Angora goats at EP weighed less (38.1 vs 41.7 kg, P = .03), and sheared less (1.90 vs 2.22 kg, P = .01), finer (36.4 vs 39.3 microns, P < .001), and less kempy (.52 vs .84%, P < .001) mohair at the February shearing than at the August shearing. No seasonal differences in body weight or in mohair production or quality were apparent at STP. The proportions of total variation in grease mohair production (30.6%), CMFP (22.2%), and AFD (15.7%) due to year effects were two to three times greater at STP than at EP. In contrast, year effects were responsible for only a small proportion (2.2 to 4.6%) of the variation in medullated fibers. The effects of rainfall accumulation within specific 6-mo growing periods were positive for BW, GFW, CFW, AFD, SD of AFD and MFP and negative for CMFP and KFP. Only the rainfall effects on SD of AFD and medullated fibers were significant (P < .05). The effects of age were positive for BW (P < .001), CMFP (P = .046), AFD (P < .001), MFP (P = .014), and KFP (P = .084) and negative for GFW (P = .046) and CFW (P = .107). This study documents influence of environment and age of goats on body weight, mohair production, and fiber characteristics.

Evaluation of the optical fibre diameter analyser (OFDA) for measuring fiber diameter parameters of sheep and goats.

The Optical Fibre Diameter Analyser (OFDA) instrument is based on automatic image analysis technology and was recently introduced to provide a rapid, accurate measurement of average fiber diameter (AFD) and diameter distribution (SD) of textile fibers. Experiments were conducted with wool and mohair in various physical forms (top, core, and staple) to compare results produced by the OFDA with two other methods of determining fiber diameter parameters: the standard projection microscope (PM) method as described by the American Society for Testing and Materials (ASTM) and the Peyer Texlab FDA 200 System (FDA200). The results show that the OFDA fiber diameter measurements were very closely related to PM measurements, and the OFDA partially overcame one shortcoming of the FDA200, overestimation of SD. The results suggest that the OFDA is a promising system for rapid and accurate evaluation of fiber diameter and its distribution.

Effects of skirting on yield, fineness, and value of wool from fine-wool range ewes.

Eighty-one mixed-age (2 to 8 yr old) Rambouillet ewes (58.5 kg, SD 5.9 kg) were randomly assigned to three treatment groups that contained similar numbers to study the effects of wool skirting on clean yield, fiber diameter, and prices received for fine wool. The sheep were managed as a single flock on an experimental ranch close to Barnhart, TX during the 4-yr study. Two fleece-skirting techniques (SK1 and SK2) were compared with a control procedure in which fleeces were not skirted before packaging (original bag, OB method). Skirted wools were higher yielding (P < .05) and contained less vegetable matter (P < .05) than skirts. However, clean yield and vegetable matter content of skirted and OB wools were not different (P > .05). Weight-averaged prices received for grease wool from the SK1, SK2, and OB treatments over the 4-yr period were 4.49, 4.36, and 3.83 $/kg, respectively. Prices received for both types of skirted wool plus skirts were higher (P < .05) than prices received for OB wool.