The combined effects of grain supplementation and tenderstretching on alpaca (Vicugna pacos) meat quality.

This study investigated the effects of feeding a mixed grain supplement and tenderstretching (TS) alpaca carcasses on meat quality. A total of 56 castrated 24month old alpacas were divided into two treatments (pasture-only, and pasture plus supplementation). Supplemented groups were fed a mixed grain ration in addition to ad lib pasture for 10weeks. Animals were slaughtered across two kill days (n=28). One half of each carcass was suspended by the pelvis (TS) prior to chilling, and the other half was Achilles tendon hung (AH). After 24h, muscles were removed and aged for 10 and 25d. TS significantly increased sarcomere length and reduced shear force and cooking loss in the m. semimembranosus. This trend was not observed in other muscles including the m. longissimus thoracis et lumborum (LL) and m. psoas major. Ageing period resulted in a marginal improvement in LL tenderness. There is clear evidence that TS improves tenderness in the hindquarter of alpacas.

The impact of gender and age on the nutritional parameters of alpaca (Vicugna pacos) meat, colour stability and fat traits.

Meat quality parameters for 50 huacaya alpacas, representing three age groups (18, 24 and 36months) and two genders (females and castrated males) were studied. Prior to chilling, samples of m. longissimus thoracis et lumborum (LL) were taken to determine isocitrate dehydrogenase activity and glycogen concentration, and further meat quality samples were taken after 24h. Alpaca meat has low levels (<1%) of intramuscular fat in the LL, m. semimembranosus and m. biceps femoris, but the level in the LL increases with animal age, with levels of desirable polyunsaturated fatty acids (PUFA) ranging from 96.3 to 136.4mg/100g. Lipid oxidisation post retail display ranged from 1.27 to 1.96MDA/kg meat. Colour stability testing indicated alpaca meat was relatively stable during retail display with day of display having no significant effect on lightness (L*), or the 630nm/580nm ratio. These results may relate to the high proportion (76%) of glycolytic and type IIX muscle fibres in LL.

Optimum number of technical replicates for the measurement of compression of lamb meat.

Up to six (average 4.63) replicate compression values were collected on cooked m. semimembranosus of lambs that had been raised at six sites across southern Australia (n=1817). Measurements on each sample were made with one of two Lloyd Texture analyser machines, with each machine having a 0.63 cm diameter plunger. Based on a log normal model with common variance on the log scale for within sample replicate results, estimates of the within sample variability of compression values were obtained, resulting in a quality control procedure for compression testing based on the coefficient of variation.

Effect of electrical stimulation and ageing period on alpaca (Vicugna pacos) meat and eating quality.

This study investigated the effects of using medium voltage (~300 V) electrical stimulation (ES) and ageing on alpaca meat. A total of 50 huacaya alpacas were distributed across three age groups (18, 24 and 36 months) and two genders (females and castrated males). At 24h post mortem the m. longissimus thoracis et lumborum (LL) and m. semimembranosus (SM) muscles were removed and aged for either 5 or 10 days. In comparison to non-ES samples, ES significantly reduced: LL purge values by 3.0% and LL shear force (SF) at 5 and 10 days (by 21.6N and ageing further reduced tenderness by 6.6N), and SM SF by 5.8 N with significant age effects observed in both ES and non-ES SM samples, such that SF increased by 0.53 N with each month increase in animal age. Consumers rated ES samples higher on tenderness, juiciness, flavour and overall rating. ES and ageing of alpaca carcasses are recommended.

A comparison of technical replicate (cuts) effect on lamb Warner-Bratzler shear force measurement precision.

The Warner-Bratzler shear force (WBSF) of 335 lamb m. longissimus lumborum (LL) caudal and cranial ends was measured to examine and simulate the effect of replicate number (r: 1-8) on the precision of mean WBSF estimates and to compare LL caudal and cranial end WBSF means. All LL were sourced from two experimental flocks as part of the Information Nucleus slaughter programme (CRC for Sheep Industry Innovation) and analysed using a Lloyd Texture analyser with a Warner-Bratzler blade attachment. WBSF data were natural logarithm (ln) transformed before statistical analysis. Mean ln(WBSF) precision improved as r increased; however the practical implications support an r equal to 6, as precision improves only marginally with additional replicates. Increasing LL sample replication results in better ln(WBSF) precision compared with increasing r, provided that sample replicates are removed from the same LL end. Cranial end mean WBSF was 11.2 ± 1.3% higher than the caudal end.

The impact of supplementing lambs with algae on growth, meat traits and oxidative status.

The current study examined the effect of supplementing lambs with algae. Forty, three month old lambs were allocated to receive a control ration based on oats and lupins (n=20) or the control ration with DHA-Gold™ algae (~2% of the ration, n=20). These lambs came from dams previously fed a ration based on either silage (high in omega-3) or oats and cottonseed meal (OCSM: high in omega-6) at joining (dam nutrition, DN). Lamb performance, carcase weight and GR fat content were not affected by treatment diet (control vs algae) or DN (silage vs OSCM). Health claimable omega-3 fatty acids (EPA+DHA) were significantly greater in the LL of lambs fed algae (125±6mg/100g meat) compared to those not fed algae (43±6mg/100g meat) and this effect was mediated by DN. Supplementing with algae high in DHA provides a means of improving an aspect of the health status of lamb meat.

Comparison of rankings for lean meat based on results from a CT scanner and a video image analysis system.

Coopworth cross lambs born over three years were examined in this study. Differences between two machines; a computer tomography (CT) scanner and a VIAScan® system for the estimation of carcase lean weight in lamb carcases was examined. The CT scanner provided a significantly higher estimate of carcase lean. The rank correlation (0.84) between the CT scanner and the VIAScan® system for the prediction of carcase lean was significant, but there was a different ranking for carcase lean depending on which machine was used. This has important ramifications for the use of VIAScan® data in the New Zealand Sheep Improvement Ltd genetic programme.

Interrelationship between measures of collagen, compression, shear force and tenderness.

This study examined the relationship between collagen content as determined by hydroxyproline assay with other measures of connective tissue, shear force and tenderness in lamb muscle. Samples were taken from both m. longissimus lumborum (LL, loin) and the m. semimembranosus (SM, topside) of 99 lambs. Sensory tenderness and compression of the LL were not correlated to any measure of collagen or connective tissue, with one exception where compression was correlated (r=-0.28; P<0.05) to the percentage of connective tissue determined by imaging. Intramuscular fat (IMF) was linearly correlated (P<0.05) to sensory tenderness and compression, such that a 1% increase in IMF increased the tenderness score by 2.3±0.83 units and reduced compression by 0.73±0.21 N. There was no correlation between SM shear force and collagen concentration. The data suggest that measurement of collagen concentration did not explain the variation in shear force and sensory tenderness observed in the meat from lambs.

Examination of the effect of ageing and temperature at rigor on colour stability of lamb meat.

A study of factors (ageing period, rigor temperature and vitamin E level) impacting on the colour stability of lamb m. longissimus thoracis et lumborum (LL) during 3 days of simulated retail display was undertaken. The LL were taken from 84 lambs from 3 slaughters. Slices of LL were measured fresh (24h post-mortem) or after ageing for 5 days in vacuum packaging. The oxy/met ratio (630/580 nm), declined with display time, and increased with increasing temperature at pH6.0. Redness (a*) values also declined with display time and a reduction in redness values was observed as LL pH at 24h post-mortem and/or pH at 18°C increased. There was no effect of ageing period or vitamin E level on the oxy/met ratio or a* values when the vitamin E level averaged 3.76 mg/kg LL. These results suggest that maximising vitamin E levels in lambs and achieving a moderate rate of pH decline will optimise colour stability irrespective of ageing period.

The interrelationship between sensory tenderness and shear force measured by the G2 Tenderometer and a Lloyd texture analyser fitted with a Warner-Bratzler head.

A comparison of peak shear force results for a Lloyd texture analyser fitted with a Warner Bratzler type of shearing head and a G2 Tenderometer was undertaken using sheep meat. The G2 is a new version of the Tenderometer that uses an electric linear motor to compress the sample, but still retains the blunt wedge-shaped "tooth". Analysis of sheep meat samples (n=121) revealed that the average G2 Tenderometer shear force results were approximately 1.2 times those for the Lloyd based on the following model; Lloyd=1.561 Tenderometer(0.84). Both instruments explained low amounts of the variation (less than 20%) in the sensory traits tenderness and overall liking. The high values for the sensory traits indicate that a wider range of samples, including samples with lower sensory scores, is required to develop robust threshold estimates so that either instrument could be use as an auditing instrument for the processing industry.

Evaluation of the Hennessy Grading Probe for use in lamb carcases.

An evaluation of the Hennessy Grading Probe (HGP) was undertaken using 557 lamb carcases for the measurement of subcutaneous fat depth (Fat C) and muscle depth (EMD; m. longissimus thoracis et lumborum (LL)) between the 12th/13th ribs. All carcases were probed on the moving chain at up to 10 carcases per min and data analysis was constrained to 320 carcases which were probed at the target site (over the greatest depth of the LL at the midpoint between the 12th and 13th ribs). Analysis of the data revealed wide variability between HGP and equivalent carcase measures, but probe type (versions GP4 and GP7) had minimal impact on the usefulness of the HGP. The HGP as used in the study does not appear to be a viable option for the Australian sheep processing industry.