Effect of housing and nutritional interventions during winter on wool attributes of Corriedale sheep

There are several factors that can directly or indirectly influence wool quality and quantity in sheep, the main elements being genetic and environmental factors. An experiment was conducted to assess the effect of different management/housing interventions during winter on wool quality and yield in Corriedale ewes. Forty healthy pregnant ewes were selected and divided into four groups (G₁, G₂, G₃, G₄) based on their body weight and parity. Throughout the study period, the groups G₁ and G₃ were reared inside the shed, while G₂ and G₄ were reared in an open shed with four-sided wire fencing and a roof shelter for direct rain/snow protection. The basic ration of all the four groups consisted of 1.25 kg roughage/head/day and 500 g concentrate/head/day. G₃ and G₄ were fed additional concentrate @ 100 g/head/day. Significant differences were observed in the crimp frequency, fibre diameter, fibre length and medullation percentage. G₂ and G₄ showed significantly (P < 0.05) higher fibre diameter but lower crimp frequency. Also, medullation percentage was significantly (P < 0.05) higher for G₂. However, the studied rearing systems showed no significant differences for wool yield, staple length, scouring yield and burr content. The study concludes that the wool quality parameters observed in sheep, exposed to cold environment, meet most of the requirements of textile sector and thus can be reared in open houses without any adverse effects.

Polymorphism in the ovine keratin-associated protein gene KRTAP7-1 and its association with wool characteristics

The keratin-associated proteins (KAPs) are structural components of wool fibers and variation in the genes encoding the KAPs can affect wool traits. In this study, sequence variation in the ovine KAP7-1 gene (KRTAP7-1) was investigated in 222 sheep across 5 different Pakistani breeds and breed crosses. Two previously identified variants (A and B) of the KRTAP7-1 coding sequence were identified. The frequency of the genotypes AA and AB was 76% and 23%, respectively, and that of BB was 1%. The association of sequence variation with various wool traits and measurements included yield (the proportion of greasy fleece weight that is clean fleece), mean staple length (MSL), wool bulk, mean fiber diameter, fiber diameter SD, the coefficient of variation of fiber diameter, medullation, the SD of medullation, the coefficient of variation of medullation, fiber opacity, the SD of opacity, and the coefficient of variation of opacity. Variation in KRTAP7-1 was found to be associated with yield (P = 0.017). The adjusted mean yield of sheep of genotype AA (n = 169) was 79.9 ± 2.72%, while that of genotype AB (n = 51) was 81.9 ± 3.37%. There was also an association between variation in KRTAP7-1 and MSL (P = 0.024), with sheep of genotype AA (n = 169) having an adjusted mean MSL of 47.3 ± 0.57 mm compared with sheep of genotype AB (n = 51, 50.9 ± 0.65 mm). Yield and MSL are both important wool production traits, hence variation in KRTAP7-1 needs to be further investigated in more sheep of differing breed.

The repeatability of textural wool handle

Merino breeders use textural greasy wool handle in ram buying and breeding decisions. The effectiveness of the current wool handle scoring system has not been objectively evaluated. The assessor repeatability of textural wool handle was quantified using three different methods of assessment (on the live animal, as a greasy wool mid-side sample, and as a clean (scoured) wool mid-side sample). The aim of the study was to determine which method of assessment is the most repeatable. Three separately defined repeatability estimates were calculated based on knowledge about the operator. The first estimate was based on the assessor repeatability from the operators used in this study. The second estimate was calculated using replicate values obtained from the same random assessor and the third estimate was based on two results from independent random assessors. The results demonstrated that the assessor repeatability was the greatest when handle was assessed on the clean wool mid-side method, followed by the greasy wool mid-side assessment, and least in the live-animal assessment. However, there was significant variation in the repeatability estimates between the four assessors used in the study. Accounting for fixed effects such as sex, sire group, birth type and rearing type, decreased the variation observed and thus had a negative impact on the assessor repeatability of textural wool handle. The results in this study indicate that non-wool constituents negatively impact on the ability of an assessor to consistently assign a score for textual handle in the greasy wool mid-side method. It is likely that the added cost and time required for scouring to assess handle in the clean state may not be economically viable in most situations. However, the increase in repeatability by assessing handle in greasy wool mid-side method compared with the live-animal assessment indicates that sheep producers should use this strategy when evaluating the trait on-farm.

Fabric and greasy wool handle, their importance to the Australian wool industry: a review

Handle-related properties of woollen fabrics have been demonstrated to be major factors affecting consumer buying attitudes. Handle is the combination of both textural and compressional attributes. Compressional handle has demonstrated processing advantages in woven and knitted fabrics. The handle of processing lots can be manipulated using a variety of technologies but direct manipulation of textural greasy wool handle pre-processing is still crude. On-farm, there is documented evidence that including handle assessment in a selection index provides additional improvements in genetic gain. However, the assessment of greasy wool handle is based on a tactile evaluation of the wool staple by sheep and wool classers, and its application is affected by a lack of framework that instructs assessors on a standard method of assessment. Once a reliable and repeatable protocol is developed, further understanding of the effect greasy wool handle has on final garment quality will be possible.

Effects of site of assessment and variation in wool quality traits on the tactile assessment of textural greasy wool handle

Variation in textural greasy wool handle across the fleece of Merino sheep was explored. Results demonstrate that there were significant differences across nine sites on the fleece. The inclusion of the covariates fibre diameter, fibre diameter co-efficient of variation, staple length, dust penetration, staple structure, greasy wool colour and resistance to compression, helped to explain some of the variation in textural greasy wool handle between sites such that site of assessment was no longer a significant factor (P = 0.065). However, in practice, those involved with clip preparation or sheep selection based on textural greasy wool handle assessment are unlikely to have these measurements available. The results highlight the importance of nominating a site of assessment when recording textural greasy wool handle.

Quality of lamb meat from the Information Nucleus Flock

The effects of production and processing factors on tenderness, and colour of lamb meat produced from 7 locations as part of the Australian Sheep Industry CRC’s Information Nucleus flock were investigated, using data from 2052 lambs slaughtered in 2007. At 24 h post-slaughter, samples of m. longissimus lumborum (LL) and m. semimembranosus (SM) were collected for measurement of intramuscular fat (IMF), myoglobin, iron and copper and fresh meat colour (L*, a*, b*) and pH at 24 h measured on the LL. pH and temperature measurements made pre-rigor were used to calculate the pH at 18°C. Tenderness was measured by LL shear force at days 1 (SF1) and 5 (SF5) post-slaughter, the shear force difference (SF-diff) and SM compression and collagen concentration were determined. Retail colour stability was assessed using over-wrapped LL under simulated retail display for 3 days, according to the change in the oxymyoglobin/metmyoglobin ratio. All traits were affected by flock and date of slaughter (P < 0.001). After 4 days of ageing, 70–95% of the LL samples from all flocks, except for one, had acceptable tenderness for consumers based on their shear force. Low IMF, high LL pH at 18°C and high pH at 24 h increased SF1 and SF5 and also had an effect on SF-diff (P < 0.001). The retail colour of 44.8% of the samples on day 3 of retail display were lower than acceptable. Retail colour was influenced by IMF, pH18 and the concentration of iron and copper (P < 0.001). In conclusion, breeding and management practices that increase muscle IMF levels and reduce ultimate pH values and processing practices that result in moderate rates of pH fall post-slaughter, improve the tenderness of lamb. Extension of retail colour stability may be antagonistic to traits associated with tenderness and nutritional traits, particularly IMF and mineral levels.

Accuracy of estimated genomic breeding values for wool and meat traits in a multi-breed sheep population

Estimated breeding values for the selection of more profitable sheep for the sheep meat and wool industries are currently based on pedigree and phenotypic records. With the advent of a medium-density DNA marker array, which genotypes ~50 000 ovine single nucleotide polymorphisms, a third source of information has become available. The aim of this paper was to determine whether this genomic information can be used to predict estimated breeding values for wool and meat traits. The effects of all single nucleotide polymorphism markers in a multi-breed sheep reference population of 7180 individuals with phenotypic records were estimated to derive prediction equations for genomic estimated breeding values (GEBV) for greasy fleece weight, fibre diameter, staple strength, breech wrinkle score, weight at ultrasound scanning, scanned eye muscle depth and scanned fat depth. Five hundred and forty industry sires with very accurate Australian sheep breeding values were used as a validation population and the accuracies of GEBV were assessed according to correlations between GEBV and Australian sheep breeding values . The accuracies of GEBV ranged from 0.15 to 0.79 for wool traits in Merino sheep and from –0.07 to 0.57 for meat traits in all breeds studied. Merino industry sires tended to have more accurate GEBV than terminal and maternal breeds because the reference population consisted mainly of Merino haplotypes. The lower accuracy for terminal and maternal breeds suggests that the density of genetic markers used was not high enough for accurate across-breed prediction of marker effects. Our results indicate that an increase in the size of the reference population will increase the accuracy of GEBV.