Relationships between temperament and a range of performance, carcass, and meat quality traits in young cattle were studied in 2 experiments conducted in New South Wales (NSW) and Western Australia (WA), Australia. In both experiments, growth rates of cattle were assessed during backgrounding on pasture and grain finishing in a feedlot. Carcass and objective meat quality characteristics were measured after slaughter. Feed intake and efficiency during grain finishing were also determined in NSW. Brahman (n = 82 steers and 82 heifers) and Angus (n = 25 steers and 24 heifers) cattle were used in the NSW experiment. In NSW, temperament was assessed by measuring flight speed [FS, m/s on exit from the chute (crush)] on 14 occasions, and by assessing agitation score during confinement in the crush (CS; 1 = calm to 5 = highly agitated) on 17 occasions over the course of the experiment. Brahman (n = 173) and Angus (n = 20) steers were used in the WA experiment. In WA, temperament was assessed by measuring FS on 2 occasions during backgrounding and on 2 occasions during grain feeding. At both sites, a hormonal growth promotant (Revalor-H, Virbac, Milperra, New South Wales, Australia) was applied to one-half of the cattle at feedlot entry, and the Brahman cattle were polymorphic for 2 calpain-system markers for beef tenderness. Temperament was not related (most P > 0.05) to tenderness gene marker status in Brahman cattle and was not (all P > 0.26) modified by the growth promotant treatment in either breed. The Brahman cattle had greater individual variation in, and greater correlations within and between, repeated assessments of FS and CS than did the Angus cattle. Correlations for repeated measures of FS were greater than for repeated assessments of CS, and the strength of correlations for both declined over time. Average FS or CS for each experiment and location (NSW or WA × backgrounding or finishing) were more highly correlated than individual measurements, indicating that the average values were a more reliable assessment of cattle temperament than any single measure. In Brahman cattle, increased average FS and CS were associated with significant (P < 0.05) reductions in backgrounding and feedlot growth rates, feed intake and time spent eating, carcass weight, and objective measures of meat quality. In Angus cattle, the associations between temperament and growth rates, feed intake, and carcass traits were weaker than in Brahmans, although the strength of relationships with meat quality were similar.

Effects and interactions of calpain-system tenderness gene markers on objective meat quality traits of Brahman (Bos indicus) cattle were quantified within 2 concurrent experiments at different locations. Cattle were selected for study from commercial and research herds at weaning based on their genotype for calpastatin (CAST) and calpain 3 (CAPN3) gene markers for beef tenderness. Gene marker status for μ-calpain (CAPN1-4751 and CAPN1-316) was also determined for inclusion in statistical analyses. Eighty-two heifer and 82 castrated male cattle with 0 or 2 favorable alleles for CAST and CAPN3 were studied in New South Wales (NSW), and 143 castrated male cattle with 0, 1, or 2 favorable alleles for CAST and CAPN3 were studied in Western Australia (WA). The cattle were backgrounded for 6 to 8 mo and grain-fed for 117 d (NSW) or 80 d (WA) before slaughter. One-half the cattle in each experiment were implanted with a hormonal growth promotant during feedlotting. One side of each carcass was suspended from the Achilles tendon (AT) and the other from the pelvis (tenderstretch). The M. longissimus lumborum from both sides and the M.semitendinosus from the AT side were collected; then samples of each were aged at 1°C for 1 or 7 d. Favorable alleles for one or more markers reduced shear force, with little effect on other meat quality traits. The size of effects of individual markers varied with site, muscle, method of carcass suspension, and aging period. Individual marker effects were additive as evident in cattle with 4 favorable alleles for CAST and CAPN3 markers, which had shear force reductions of 12.2 N (P < 0.001, NSW) and 9.3 N (P = 0.002, WA) in AT 7 d aged M. longissimus lumborum compared with those with no favorable alleles. There was no evidence (all P > 0.05) of interactions between the gene markers, or between the hormonal growth promotant and gene markers for any meat quality traits. This study provides further evidence that selection based on the CAST or CAPN3 gene markers improves meat tenderness in Brahman cattle, with little if any detrimental effects on other meat quality traits. The CAPN1-4751 gene marker also improved beef tenderness without affecting other objective meat quality traits in heterozygous cattle compared with homozygotes for the unfavorable allele.

Experiments were conducted concurrently at 2 locations to quantify effects and interactions of calpain-system tenderness gene markers on growth, efficiency, temperament, and carcass traits of Brahman cattle. Cattle were selected at weaning from commercial and research herds based on their genotype for commercially available calpastatin (CAST) and calpain 3 (CAPN3) gene markers for beef tenderness. Genotypes for mu-calpain gene markers (CAPN1-4751 and CAPN1-316) were also determined and included in statistical analyses. The New South Wales (NSW) herd was composed of 82 heifers and 82 castrated male cattle with 0 or 2 favorable alleles for CAST and CAPN3. The Western Australia (WA) herd was composed of 173 castrated male cattle with 0, 1, or 2 favorable alleles for CAST and CAPN3. One-half of the cattle at each site were implanted with a hormonal growth promotant (HGP: Revalor-H) during grain finishing. Cattle were backgrounded at pasture for 6 to 8 mo and grain-fed for 117 d (NSW) or 80 d (WA) before slaughter. Individually, or in combination with each other and with CAPN1-4751 status, CAST and CAPN3 status had no significant (all P > 0.05) effects on BW, growth, feed efficiency, or temperament traits. The only significant effect of CAST or CAPN3 on carcass characteristics was a small increase in rib fat with increasing number of favorable CAST alleles (P = 0.042) in the WA herd. There were no significant interactions (all P > 0.05) between the markers, or between the markers and sex or HGP treatment apart from CAST x HGP for area of the M. longissimus lumborum (P = 0.024) in the NSW experiment. Favorable CAST or CAPN3 alleles appear unlikely to have detrimental effects on growth, efficiency, temperament, or carcass characteristics of Brahman cattle; however, some effects evident for CAPN1 status indicate the need for further production studies on effects of these markers. Overall, the findings of the present study indicate that calpain-system gene markers are suitable for use in marker-assisted selection to improve meat tenderness in Brahman cattle without negative effects on other production and carcass characteristics.

Abstract. Effects of hormonal growth promotant (HGP) implantation on liveweight, carcass and meat quality measurements were examined using 80 Angus yearling cattle. After entry to the feedlot, 40 steers and 40 heifers were implanted with Revalor-S (28 mg oestradiol and 140 mg trenbolone acetate) and Revalor-H (20 mg oestradiol, 200 mg trenbolone acetate), respectively. Cattle were slaughtered after 55 and 65 days on feed. Samples from the Mm. longissimus dorsi, biceps femoris (the cap and body portions), gluteus medius (the eye and D portions), infraspinatus and triceps brachii were prepared for sensory testing after aging for 5 and 21 days after slaughter. A total of 854 muscle samples were cooked by grill (601) or roast (253) methods and served to consumers using the Meat Standards Australia taste panel protocols.When adjusted to the same initial liveweight, implantation with Revalor-H and Revalor-S resulted in a 4 and 7% increase in slaughter weight, respectively. Implantation resulted in an increased ossification score in steers (P < 0.05), but not in heifers. There was a significant interaction (P < 0.05) between HGP implantation and days aged for shear force. There was a small effect of HGP implants on compression (P < 0.05), but not on cook loss and intramuscular fat percentage. Muscles differed in their response to HGP implantation (P < 0.05) for tenderness, overall liking and palatability scores. Muscles also differed in their aging rates after slaughter (P < 0.05). The greatest response in sensory scores to HGP implantation was found in those muscles that had the highest aging rates. Possible mechanisms by which muscles differed in their response to HGP implantation are discussed.

As a component of the second term of the Cooperative Research Centre (CRC) for Cattle and Beef Quality, a project to further test and validate the effects of varying nutritional growth paths pre-finishing and slaughter on cattle of varying genetic potential for meat yield and eating quality was designed and implemented. This project, ‘Regional Combinations’, was a multi-site experiment, using Bos taurus cattle generated at 4 locations across southern Australia. The design of imposing different growth paths between weaning and finishing on cattle with specific genetic potential is common across sites. Treatment and interaction effects on beef production and meat quality were examined within and across sites. This paper describes the experimental designs, generation of experimental cattle at the various sites and the measurements, collection and storage of the data for multi-site analyses.

Abstract. The effect of several different hormonal growth promotant (HGP) implant strategies on the palatability and carcass traits of different muscles in beef carcasses was investigated using samples from heifer and steer carcasses from a Bos indicus composite breed. In experiment 1, there were seven different implant strategies evaluated in heifers that were given different combinations of up to three implants (implanted at weaning, during backgrounding and at feedlot entry). A total of 112 heifers were slaughtered and 11 muscles or portions were collected from both sides [Mm. adductor femoris, gracilus, semimembranosus, longissimus dorsi lumborum, triceps brachii caput longum, semispinalis capitis, serratus ventralis cervicis, spinalis dorsi, biceps femoris (syn. gluteobiceps), tensor fasciae latae, gluteus medius (both the 'D' and the 'eye' portions) rectus femoris, vastus intermedius, vastus lateralis and vastus medialis]. These muscles were used to prepare a total of 1030 sensory samples which were aged for either 7 or 21 days and frozen. Thawed samples were cooked using different cooking methods (grill, roast and stir frying) before being evaluated by a consumer taste panel that scored samples for tenderness, juiciness, like flavour and overall liking. Experiment 2 used the steer portion from the same calving, which were treated to a similar array of HGP strategies, except that they were given up to four implants between weaning and slaughter at 3 years of age. In experiment 2, there was a total of 12 different HGP implant strategies tested. At boning, three muscles (Mm. psoas major, longisimuss dorsi thoracis and lumborum portions) were collected from each of 79 carcasses with a total of 237 steak samples that consumers tested as grilled steaks.For both experiments, the mean of the HGP implant strategies resulted in increased ossification scores (P < 0.05) and decreased marbling scores (P < 0.05) compared with the controls, with the effect on ossification being much larger in the older steer groups. In both experiments, the different HGP strategies decreased (P < 0.05) all sensory scores compared with the controls, for all cooking method and muscle combinations. In experiment 1, there was no interaction between the mean HGP effect and muscle (P > 0.05), and aging rates differed among the muscles (P < 0.05). In experiment 2, there was a significant (P < 0.05) muscle · HGP treatment interaction, with a decrease in tenderness score due to HGP implant strategies in the M. longisimuss thoracis and lumborum portions, compared with no significant effect in the M. psoas major. For both experiments, there were no significant differences among the different implantation strategies on sensory scores (P > 0.05).

ABSTRACT:We investigated the effects of calpainsystem genetic markers on consumer beef quality ratings, including interactions of marker effects with hormonal growth promotant (HGP) use and tenderstretch hanging. Brahman cattle in New South Wales (NSW; n = 164) and Western Australia (WA; n = 141) were selected at weaning from commercial and research herds to achieve balance and divergence in calpastatin (CAST) and calpain 3 (CAPN3) gene marker status. Genotypes for μ-calpain (CAPN1-4751 and CAPN1-316) were also determined. Angus cattle (49 in NSW, 17 in WA) with favorable CAST and CAPN3 alleles, balanced for CAPN1-316 status, were also studied. Half the cattle at each site had HGP (Revalor-H, containing 200 mg trenbolone acetate and 20 mg 17β-estradiol) implants during grain fi nishing. One side of each carcass was suspended from the Achilles tendon (AT) and the other from the pelvis [tenderstretch (TS)]. Meat Standards Australia consumer panels scored 7-d aged striploin steaks from both AT and TS sides, and 7-d aged rump and oyster blade steaks from the AT side of each carcass. Two favorable CAST alleles increased tenderness ratings of AT-striploin, TS-striploin, rump, and oyster blade steaks by, respectively, 6.1, 4.2, 4.2, and 3.1 units, and overall liking by 4.7, 2.8, 2.9, 3.7 (all P < 0.04). Two favorable CAPN1-4751 alleles increased tenderness of AT-striploin, TS-striploin, and rump steaks by 6.5, 4.3, and 3.9 units, and overall liking by 5.6, 3.1, and 4.1 units. Two favorable CAPN3 alleles improved rump steaks by 3.7, 3.3, 3.7, and 3.5 units, for tenderness, juiciness, liking the fl avor, and overall liking. There were no signifi cant CAPN1-316 effects. The effect of HGP was greatest for the AT-striploin (reducing tenderness and overall liking by 8.2 units, P < 0.001), then TS-striploin (-5.6 for tenderness, -5.0 for overall liking, P < 0.001), and then rump (-4.4 for tenderness, -3.3 for overall liking, P < 0.007). Processing conditions differed considerably between NSW and WA. Rump steaks from NSW scored about 10 units greater than those from WA, but Angus and Brahman steaks from the same location with the same marker alleles had similar scores. In contrast, NSW Angus striploin steaks scored about 15 units greater for tenderness and overall liking (P < 0.001) than cattle with the same marker alleles at the other 3 location × breed combinations, which had generally similar scores. Therefore, calpain-system gene markers have benefi cial effects on eating quality, consistent with our previous fi ndings for objective meat quality.

Two hundred and forty sheep of about 15 months of age were used in this experiment to investigate the impact of dentition category on objective and sensory meat quality. The lambs were categorised into 3 dentition classes (category 1, milk teeth; category 2, partial eruption of permanent teeth; and category 3, both permanent teeth fully erupted to the height of the central lateral milk teeth). The study was conducted on 3 farms with flocks representing the 3 genotypes that contribute to the prime lamb industry in Australia: Farm A (Merino × Merino), Farm B (first cross, Border Leicester sire × Merino ewe), and Farm C (second cross, Poll Dorset sire × Border Leicester–Merino ewe). Of the 19 meat quality attributes assessed in sheep from the 3 farms, only 1 attribute in sheep from 1 farm showed a significant deterioration in meat quality as a result of lambs progressing from dentition category 1 to 2. This was an increase in myoglobin content in lambs from Farm B (P<0.05). Many of the attributes assessed showed changes that could be considered as positive for meat quality as the lambs progressed from milk teeth to partially erupted and even to fully erupted teeth. Lambs from dentition category 3 had heavier carcass weights and higher dressing percentages compared with lambs from dentition categories 1 and 2 (P<0.05). The M. longissimus dorsi et lumborum (LD) of lambs from dentition category 3 had a lower surface lightness (L*) value, a higher myoglobin content and a lower cooking loss compared with lambs from dentition categories 1 and 2 (P<0.05). Consumer sensory assessment found the LD from lambs in dentition category 1 to have a lower acceptability score for tenderness compared with the LD from lambs in dentition category 3 (P<0.05) and a lower acceptability score for juiciness, a lower consumer rating and a lower sheep eating quality score compared with the LD from lambs in dentition categories 2 and 3 (P<0.05). The results indicate that for the range of sheep studied, meat from young sheep with partially erupted teeth is unlikely to be inferior in eating quality than the meat currently classified as lamb.