Periconception and First Trimester Diet Modifies Appetite, Hypothalamic Gene Expression, and Carcass Traits in Bulls.

Nulliparous yearling beef heifers (n=360) were used to evaluate the effects of maternal dietary protein during the periconception and first trimester periods of gestation on postnatal growth, feedlot performance, carcass characteristics, and the expression of genes associated with appetite in the arcuate nucleus of their male progeny. Heifers were individually fed a diet of 1.18g crude protein (CP)/day High protein (HPeri) or 0.62g CP/day Low protein (LPeri) beginning 60days before conception. From 24 to 98days post-conception (dpc), half of each treatment group changed to the alternative post-conception diet and were fed 1.49g CP/day (HPost) or 0.88g CP/day (LPost) yielding four treatment groups in a 2×2 factorial design. From day 98 of gestation, heifers received a common diet until parturition. Calves were weaned at 183days and developed on pasture before feedlot entry. Bulls underwent a 70-day Residual Feed Intake (RFI) feedlot test commencing at 528days of age. Feedlot entry and final body weight (BW), feedlot average daily gain (ADG) and RFI were not different (p>0.05). Progeny of dams that had a change in diet (LPeri/HPost and HPeri/LPost) had 9% higher daily dry matter intake (DMI) during the RFI test (p<0.05) than progeny of dams that received low diet throughout both the peri-conception period and first trimester (LPeri/LPost). Further, mRNA expression of the appetite-stimulating agouti-related protein (AGRP) was increased in the arcuate nucleus of High Peri/LPost bulls (p<0.05). Longissimus dorsi muscle cross sectional area, carcass dressing percentage, and estimated retail beef yield (RBY) were all higher (p<0.05), and rump (P8) fat tended to be lower (p=0.07), for bulls from HPost dams despite no difference in carcass weight (p<0.05). This study is of commercial importance to the livestock industry as specific periods of maternal dietary supplementation may increase feed intake, enhance progeny muscling, and alter fat deposition leading to improvement in efficiency of meat production in beef cattle.

Ageing-freezing/thaw process affects blooming time and myoglobin forms of lamb meat during retail display.

Loins from fifty-six lambs were allocated to 2 ageing times (6 and 12 days post mortem) and a Frozen treatment (6 days of ageing followed by freeze/thaw process). Instrumental colour parameters, chroma, hue angle, 630/580 and myoglobin isoforms were assessed repeatedly every 5 min during the first 40 min and every 10 min from 40 to 120 min after surface cutting. Colour stability was measured instrumentally during 4 consecutive days of simulated retail display. L* values were lower for Frozen treatment compared to meat aged for 6 and 12 days. Redness increased at a lower rate for Frozen treatment compared to samples aged for 6 days up to the breakpoint and took a longer time to stabilize. Meat subjected to the ageing-freezing/thaw process required a longer time to reach a fully bloomed status than meat aged up to 12 days post mortem. The ageing-freezing/thaw process improved the redness of lamb meat displayed for 4 days in cold storage.

Genetic correlations between meat quality traits and growth and carcass traits in Merino sheep1.

Genetic correlations between 16 meat quality and nutritional value traits and live weight at various ages, live ultrasound fat and muscle depth, carcass measures, and carcass dissection traits were estimated for Merino sheep in the Information Nucleus (IN). Genetic correlations between live weight at various ages and the carcass traits are also reported. The IN comprised 8 genetically linked flocks managed across a range of Australian sheep environments. Meat quality traits included between 1,200 and 1,300 records for progeny from over 170 sires for intramuscular fat (IMF), lean meat yield (LMY), shear force (SF5), pH, meat color, and meat nutritional value traits including iron and zinc levels and long-chain omega-3 and omega-6 polyunsaturated fatty acid levels. The genetic correlations indicated that selection of Merino sheep to either reduce fat or increase muscle using ultrasound assessments will result in little change in IMF and SF5. Myoglobin levels would tend to be reduced following selection for reduced ultrasound fat depth (0.35 ± 0.21, 0.43 ± 0.14), whereas increases in myoglobin levels would occur due to selection for increased ultrasound muscle depth (0.25 ± 0.24, 0.38 ± 0.15). Selection for increased live weight will result in favorable correlated responses in hot carcass weight (0.76 to 0.97), dressing percentage (0.13 to 0.47), and carcass muscle (0.37 to 0.95), but unfavorable responses of increases in carcass fatness (0.13 to 0.65) and possible small reductions in muscle oxidative activity (-0.13 ± 0.14 to -0.73 ± 0.33) and iron content (-0.14 ± 0.15 to -0.38 ± 0.16), and a possible deterioration of shear force from selection at later ages (0.15 ± 0.26, 0.27 ± 0.24). Negligible changes are generally expected for LMY and meat color traits following selection for increased live weight (most genetic correlations less than 0.20 in size). Selection for increased LMY would tend to result in unfavorable changes in several aspects of meat quality, including reduced IMF (-0.27 ± 0.18), meat tenderness (0.53 ± 0.26), and meat redness (-0.69 ± 0.40), as well as reduced iron levels (-0.25 ± 0.22). These genetic correlations are a first step in assisting the development of breeding values for new traits to be incorporated into genetic evaluation programs to improve meat production from Merino sheep and other dual-purpose sheep breeds.

Meat quality attributes of Agile Wallabies.

Meat quality traits of Agile Wallaby (Macropus agilis) M. longissimus (loin) and M. semimembranosus (topside) were investigated. Both muscles exhibited a relatively high pH (>5.7) and dark colour (L*-, a*-, and b*-values). Aging the loins from 2 to 21days p.m. had a significant effect on shear force. However, the results regarding shear force, myofibrillar fragmentation index (MFI) and degradation of desmin and troponin-T suggested that the aging response largely occurred within 2days p.m. Suspension of carcasses from one leg resulted in a side effect on shear force of the loin at 2 and 7days p.m., but not on sarcomere length or MFI. Topsides from the free hanging leg exhibited lower shear force values (33 vs 42N) and greater sarcomere lengths (2.51 vs 1.84µM). Tenderness, juiciness, flavour and overall liking were higher for loins than topsides. Sensory scores for the loin and topside were slightly lower and similar, respectively, to those reported for lamb.

The relationship between shear force, compression, collagen characteristics, desmin degradation and sarcomere length in lamb biceps femoris.

This study aimed to identity the relationships between known variants of tenderness (collagen content (total and soluble), desmin degradation and sarcomere length) and shear force and compression in the biceps femoris aged for 14days from 112 mixed sex lambs. Desmin degradation was related to compression (P<0.05) such that as desmin degradation increased compression decreased. Sarcomere length (SL) was related to shear force (P<0.05), such that as SL increased shear force declined. Shear force was also related to compression (P<0.05), and soluble collagen (P<0.05), with male lambs producing higher shear force values than females (4.4±1.72N: P<0.05) when adjusted for compression, sarcomere length and soluble collagen. The findings from this experiment indicate that the known variants (soluble collagen, sarcomere length and desmin degradation) are related to shear force and compression in ovine biceps femoris.

Impact of high oxygen and vacuum retail ready packaging formats on lamb loin and topside eating quality.

Lamb steaks from semimembranosus (SM) and longissimus thoracis et lumborum (LTL) muscles were allocated to three different packaging treatments - Darfresh® vacuum skin packaging (VSP), Darfresh® Bloom packaging (80% O2:20% CO2; Hi-Ox-DB) or high oxygen modified atmosphere packaging (80% O2:20% CO2; Hi-Ox-MAP) - and stored in simulated retail display for 5 or 10days and then subjected to consumer sensory and chemical analyses. Hi-Ox-MAP and Hi-Ox-DB samples had lower tenderness, flavor, juiciness and overall liking scores and higher TBARS values, compared to VSP. Hi-Ox-MAP samples deteriorated in juiciness and flavor between 5 and 10days. Hi-Ox-MAP LTL samples had a lower myofibrillar fragmentation index, consistent with reduced proteolysis, although desmin proteolysis and desmin and troponin-T cross-linking were not influenced by packaging. The LTL exhibited greater desmin degradation and reduced desmin cross-linking relative to the SM, supporting the higher tenderness scores in this muscle. Direct packaging of lamb into retail ready VSP may provide the sheepmeat industry with greater flexibility while increasing consumer satisfaction.

The influence of peri-conception and first trimester dietary restriction of protein in cattle on meat quality traits of entire male progeny.

Primiparous Santa Gertrudis heifers were used to evaluate the effects of gestational dietary protein content on meat quality traits of 20month old bull progeny (n=40). At -60d before AI, heifers were randomly allocated to HIGH or LOW protein diet (HPERI and LPERI). From 24dpc, half of each treatment group changed to an alternative post-conception HIGH or LOW protein diet (HPOST and LPOST). LPERI and LPOST diets resulted in higher shear force of the semitendinosus muscle than HPERI (P=0.053) and HPOST (P=0.003), respectively. Heat-soluble collagen in the semitendinosus muscle was lower (P=0.019) for LPERI than HPERI. Collagen and tenderness of the longissimus muscle were not affected by dam nutrition (P>0.05). Color, pH, sarcomere length, cooking loss, compression values, desmin and troponin-T degradation, fiber type, intramuscular fat and polyunsaturated fatty acid content were not affected by dam nutrition during the peri-conception and first trimester gestational period (P>0.05).

Do sarcomere length, collagen content, pH, intramuscular fat and desmin degradation explain variation in the tenderness of three ovine muscles?

The longissimus (n=118) (LL), semimembranosus (n=104) (SM) and biceps femoris (n=134) (BF) muscles were collected from lamb and sheep carcases and aged for 5days (LL and SM) and 14days (BF) to study the impact of muscle characteristics on tenderness as assessed by shear force (SF) and sensory evaluation. The impact of gender, animal age, collagen content, sarcomere length (SL), desmin degradation, ultimate pH and intramuscular fat (IMF) on tenderness was examined. The main factors which influenced SF of the LL were IMF, SL and desmin degradation, but for sensory tenderness, IMF, ultimate pH and gender were the main factors. The SF and sensory tenderness of the SM was best predicted by the degree of desmin degradation. For the BF soluble collagen and animal age both influenced SF. Different factors affect tenderness across muscles and not one prediction model applied across all muscles equally well.

The effect of retail packaging method on objective and consumer assessment of beef quality traits.

This study evaluated the effect of 7days of modified atmosphere packaging (MAP: 80% O2, 20% CO2) or skin packaging (no oxygen) of beef M. longissimus steaks after 1 or 7days of ageing in vacuum on objective and sensory meat quality traits and degradation of desmin. Shear force was negatively affected by MAP after both 1 and 7days of ageing in vacuum (P<0.005). Sensory evaluation of grilled steaks revealed significantly negative effects of MAP on sensory traits, resulting in an overall decrease of 8 points in the Meat Standards Australia (MSA) eating quality score (MQ4). Desmin degradation was not affected by packaging method, suggesting that the toughening effect of high-oxygen MAP is not due to inhibition of postmortem proteolysis. The results of this study and others suggest that packaging method should be incorporated as a variable in the MSA grading system. Further research to quantify the impact of oxidative cross-linking of proteins on tenderness appears warranted.

Explaining the variation in lamb longissimus shear force across and within ageing periods using protein degradation, sarcomere length and collagen characteristics.

Meat tenderness is known to be affected by sarcomere length (SL), proteolysis and collagen content (CC). Sixty lambs were slaughtered and the Longissimus muscle was sampled. Samples for shear force (SF), SL, proteolysis indicators (desmin degradation, particle size: PS) and CC were taken after the allotted ageing periods (1, 7, and 14 days). PS explained a large part of the variation in shear force (approximately 34%) when modelled across ageing periods. Other factors (CC, SL) combined with proteolysis indicators (PS, desmin degradation) explained just under 40% of the variation in shear force. Within ageing periods SL explained a small, but significant, part of the variation in shear force after 14 days of ageing (8%) and at day 1 of ageing desmin degradation explained 17% of the variation in shear force. Methods to improve the tenderness of lamb longissimus muscle should focus on increasing the extent of post-mortem proteolysis, when processing conditions are sufficient to prevent muscle fibre shortening.

Exogenous proteases for meat tenderization.

The use of exogenous proteases to improve meat tenderness has attracted much interest recently, with a view to consistent production of tender meat and added value to lower grade meat cuts. This review discusses the sources, characteristics, and use of exogenous proteases in meat tenderization to highlight the specificity of the proteases toward meat proteins and their impact on meat quality. Plant enzymes (such as papain, bromelain, and ficin) have been extensively investigated as meat tenderizers. New plant proteases (actinidin and zingibain) and microbial enzyme preparations have been of recent interest due to controlled meat tenderization and other advantages. Successful use of these enzymes in fresh meat requires their enzymatic kinetics and characteristics to be determined, together with an understanding of the impact of the surrounding environmental conditions of the meat (pH, temperature) on enzyme function. This enables the optimal conditions for tenderizing fresh meat to be established, and the elimination or reduction of any negative impacts on other quality attributes.

Health beneficial long chain omega-3 fatty acid levels in Australian lamb managed under extensive finishing systems.

The variation in levels of the health claimable long chain omega-3 fatty acids, eicosapentaenoic acid (EPA, 20:5n-3) plus docosahexaenoic acid (DHA, 22:6n-3) across production regions of Australia was studied in 5726 lambs over 3 years completed in 87 slaughter groups. The median level of EPA plus DHA differed dramatically between locations and sometimes between slaughters from the same location. The ratio of EPA plus DHA from lambs with high values (97.5% quantile) to lambs with low values (2.5% quantile) also differed dramatically between locations, and between slaughters from the same location. Consistency between years, at a location, was less for the high to low value ratio of EPA plus DHA than for the median value of EPA plus DHA. To consistently obtain high levels of omega-3 fatty acids in Australian lamb, there must be a focus on lamb finishing diets which are likely to need a supply of α-linolenic acid (18:3n-3), the precursor for EPA and DHA.

The effects of the myostatin g+6723G>A mutation on carcass and meat quality of lamb.

This study evaluated the effects of the myostatin g+6723G>A mutation on carcass and meat quality traits of lamb (AA: n=5; AG: n=8; GG: n=9). Dressing percentage was positively affected by the mutation with homozygotes for the mutation having the highest yield. Regarding carcass composition, there was a significant increase in the proportional weights of the loin and hindquarter muscles. Objective meat quality traits of the M. longissimus lumborum (LL) and M. semimembranosus (SM) were not significantly affected. For the SM, toughness (shear force and compression) tended to be lowest for homozygotes for the mutation. The myostatin g+6723G>A mutation did not affect sensory meat quality traits of grilled steaks for the LL, but resulted in a significant improvement in eating quality for the SM. Given the number of animals in this study, the robustness of the outcome of this study with regard to the effects on meat quality and its causes requires further investigation.

Rapid tenderisation of lamb M. longissimus with very fast chilling depends on rapidly achieving sub-zero temperatures.

A study was undertaken to determine whether variations within the defined temperature-by-time profile for very fast chilling (VFC), might explain variations in tenderness found with VFC. Loins from 32 lambs were subjected to one of five cooling regimes; defined by the average temperature between the meat surface and centre reached at a specific time post mortem. These were: -0.3 °C at 22 h (Control), 2.6 °C at 1.5 h (Fast(supra-zero)), 0.7 °C at 5.5 h (Slow(supra-zero)), -1.6 °C at 1.5 h (Fast(sub-zero)) and -2.3 °C at 5.5 h (Slow(sub-zero)), respectively. Shear force values considered very tender by consumers (less than 50 N, MIRINZ tenderometer) were found 2 days post mortem in Fast(sub-zero) loins only. Both time and temperature at the end of the cooling period contributed to variations in shear force. To achieve low shear force, the loins needed to be cooled to less than 0 °C at 1.5 h post mortem.

Tenderness of pre- and post rigor lamb longissimus muscle.

Lamb longissimus muscle (n=6) sections were cooked at different times post mortem (prerigor, at rigor, 1dayp.m., and 7 days p.m.) using two cooking methods. Using a boiling waterbath, samples were either cooked to a core temperature of 70 °C or boiled for 3h. The latter method was meant to reflect the traditional cooking method employed in countries where preparation of prerigor meat is practiced. The time postmortem at which the meat was prepared had a large effect on the tenderness (shear force) of the meat (P<0.01). Cooking prerigor and at rigor meat to 70 °C resulted in higher shear force values than their post rigor counterparts at 1 and 7 days p.m. (9.4 and 9.6 vs. 7.2 and 3.7 kg, respectively). The differences in tenderness between the treatment groups could be largely explained by a difference in contraction status of the meat after cooking and the effect of ageing on tenderness. Cooking pre and at rigor meat resulted in severe muscle contraction as evidenced by the differences in sarcomere length of the cooked samples. Mean sarcomere lengths in the pre and at rigor samples ranged from 1.05 to 1.20 µm. The mean sarcomere length in the post rigor samples was 1.44 µm. Cooking for 3 h at 100 °C did improve the tenderness of pre and at rigor prepared meat as compared to cooking to 70 °C, but not to the extent that ageing did. It is concluded that additional intervention methods are needed to improve the tenderness of prerigor cooked meat.

Particulate metmyoglobin reducing activity and its relationship with meat color.

There is controversy about the effect of storage time on metmyoglobin (MetMb) reducing activity in the sarcoplasmic fraction of meat and the role of this reducing activity in maintaining the color of red meat. The presence of metmyoglobin reducing activity in the myofibrillar fraction of muscle extracts was investigated as a possible reason for this controversy. NADH-dependent MetMb reducing activity was found in the particulate fraction of meat following sedimentation of a meat homogenate at 35 000g. There was 5.8 times more MetMb reducing activity in the particulate fraction compared with that of the sarcoplasmic (supernatant) fraction. The presence of metmyoglobin reducing activity in the myofibrils (MMRA), defined as the activity in the sediment after centrifugation of a meat homogenate at 2 000g, was confirmed. The myofibrillar fraction contained 63% of the total MetMb reducing activity available in the meat. The relationship between muscle MetMb reducing activities and meat color parameters was investigated in a beef patties system. The particulate MetMb reducing activity (PMRA) in beef patties was found to be a good indicator of the total metmyoglobin reducing activity in meat and was positively correlated with the color parameters of the patties, suggesting that PMRA may be associated with red meat color of meat patties.