. 2011. Modification of muscle inherent properties through age at slaughter, growth promotants and breed crosses. Can. J. Anim. Sci. 91: 635Á648. A 2 4 factorial experiment tested the interactions of slaughter age (12Á13 or 18Á20 mo), growth hormone use, b-adrenergic agonist (b-AA) use and breed cross [HerefordÁAberdeen Angus (HAA) or CharolaisÁRed Angus (CRA)] on the composition, fibre types, and connective tissue characteristics of m. semitendinosus (ST) and m. gluteus medius (GM) from 112 crossbred steers. Muscle weights increased with slaughter age, implantation and CRA genetics (PB0.05), but were not affected by ractopamine hydrochloride (RAC) (P 0.10). Animal age increased fast glycolytic (FG) and decreased fast oxidative glycolytic (FOG) fibre percentages by 7.2 and 6.6%, respectively, in the ST and increased slow oxidative (SO) and FOG fibre areas in both muscles (PB0.05). Cross-sectional areas of all fibre types were increased in the ST with implantation. In the GM, implantation increased SO (3.1%) and reduced FOG (3.2%) fibre percentages, while RAC reduced the SO (3.8%) and increased the FG (6.1%) fibre percentages (P B0.05). Only GM total collagen content increased with slaughter age (PB0.05), but collagen solubility decreased with slaughter age for both muscles (PB0.05). CRA genetics increased FG percentage in the GM of yearling-fed steers and increased moisture and protein and reduced fat contents of both muscles (PB0.05). In the muscles studied, IMP, slaughter age and animal genetics induced greater changes in muscle inherent properties than RAC.

Girard, I., Aalhus, J. L., Basarab, J. A., Larsen, I. L. and Bruce, H. L. 2012. Modification of beef quality through steer age at slaughter, breed cross and growth promotants. Can. J. Anim. Sci. 92: 175–188. A 23 factorial experiment tested the interactions of slaughter age (12–13 or 18–20 mo), growth implants use (Component E-S, TE-S), ractopamine hydrochloride (RAC) feed supplementation use and breed cross [Hereford–Aberdeen Angus (HAA) or Charolais–Red Angus (CRA)] on pH, temperature, objective colour measurements, relative myoglobin states, sarcomere lengths, shear force, and water losses of m. semitendinosus (ST) and m. gluteus medius (GM) from 112 crossbred steers. In the ST, age affected objective colour measurements by increasing chroma and decreasing lightness (L*) and hue angle (P<0.05). Metmyoglobin (MMB) content of the ST also increased with steer age (P<0.05). In the GM, yearling-fed steers had greater MMB content than calf-fed steers, while hue angle varied the opposite way (P<0.05). Other variations in meat colour and myoglobin contents were more complex in the GM than the ST as they involved three-way interactions between the different treatments. Shear force and purge loss of the ST increased with implantation (P<0.05) with no change in sarcomere length (P>0.05). Shear force standard deviation was similar for breed crosses when yearling-fed but greatest for CRA breed cross when calf-fed (P<0.05). In both muscles, purge loss was increased by RAC supplementation (P<0.05). RAC supplementation did not affect sarcomere length and shear force in both muscles (P>0.10). In the GM, shear force increased with age and with CRA genetics (P<0.05). Results indicated that producers seeking to reduce beef toughness should consider using British crossbreds, exclude the use of hormonal implants and slaughter process steers at 12 to13 mo of age.

Rodas-González, A., Juárez, M., Robertson, W. M., Larsen, I. L. and Aalhus, J. L. 2013. Characterization of Canadian grade standards and lean yield prediction for cows. Can. J. Anim. Sci. 93: 99–107. Commercial carcasses (n=120) were selected to benchmark the current Canadian grading system for cows (D1, D2, D3, D4;>50% ossification) in comparison to A/AA grades youthful carcasses [over (OTM) and under (UTM) 30 mo of age based on dentition but <50% ossification]. With the exception of the D3 and D4 grades, D1 and D2 carcass grades had similar carcass yield attributes compared with OTM and UTM carcasses; however, rib-eye area from UTM carcasses was the largest (P<0.05), followed by D1, D2 and OTM. As expected, both OTM and UTM grades had lower ossification scores (P<0.05); however, D4 grade showed the highest marbling score (P<0.05). For carcass composition, compared with all other grades, the D3 grade had the highest proportion of lean (P<0.05) due to a lower proportion of dissectible fat (P<0.05); however, it had the lightest carcass weight (P<0.05). Using simple measures of carcass characteristics (grade fat, rib-eye area, marbling and ossification) a prediction equation to estimate lean yield (R 2=0.825; Cp=4.31) could be used to more accurately assess carcass value in cows; however, validation of the equation on a separate population would be required before its application.

Avilés, C., Juárez, M., Larsen, I. L., Rodas-González, A. and Aalhus, J. L. 2014. Effect of multiple vacuum packs on colour development and stability in beef steaks. Can. J. Anim. Sci. 94: 63–69. The aim of this study was to compare the colour stability of steaks from longissimus dorsi muscle previously submitted to four treatments of vacuum packaging and aged for 15 d. Muscle portions were either vacuum packed and aged for 15 d (NRP), or repacked after 2 h (RP2h), 8 d (RP8d) and after 2 h and 8 d (RP2h+8d). Purge loss values from RP8d and RP2h+8d treatments were higher (P=0.019) than those from NRP and drip loss was higher (P=0.001) for RP2h and RP8d. Colour changes during a 30-min period of exposure to atmospheric oxygen immediately after opening the packages were similar for repackaged-aged steaks and NRP steaks (P>0.05). Nevertheless, colour stability during subsequent retail display under atmospheric air conditions was affected by the packaging treatment. The decrease in chroma values (P=0.043) and the increase in hue (P=0.011) between day 3 and day 6 was minimum for RP2h+8d, compared with NRP, RP2h and RP8d. Also, the proportion of pigment in the myoglobin form in these three treatments dramatically increased from day 3 to day 6, while no effect was observed for RP2h+8d (P=0.005). Similarly, the decrease over time in the proportion of pigment in the oxymyoglobin form in meat from the RP2h+8d treatment was much lower (P=0.002) than for the other three packaging treatments. Changes in colour stability associated with multiple vacuum packagings may confound results in experimental designs. Thus, if beef colour is to be evaluated, repeated vacuum packaging should be limited.

The relation of carcass physiological maturity to meat quality in the Canadian Bison Grading System. Can. J. Anim. Sci. 94: 55Á62. A total of 119 bull (n 062) and heifer (n 057) bison carcasses were selected to determine the effectiveness of youthful to intermediate physiological maturity [ossification at the 9th/10th/11th thoracic spinous processes (550%; 51Á65%; 66Á80%)] range to accurately classify bison carcasses with respect to quality. Carcasses were classified into three maturity groups according to ossification at the 9th/10th/11th thoracic spinous processes (550%; 51Á65%; 66Á80%). Carcass, meat quality and sensory evaluation data were then collected. Bull carcasses were significantly (PB0.0001) heavier than heifers (308.0 vs. 228.6 kg), while heifers had higher (PB0.0001) marbling scores than bulls (368 vs. 289). For both genders, ossification group had little or no impact (P!0.05) on any of the meat quality traits. Gender had an impact on the shear force values for both fresh (PB0.0001) and frozen/thawed (P00.0002) samples, with bulls having higher values than heifers. Panellists detected differences between heifers and bulls in initial tenderness (PB0.0001; 7.11 vs. 6.27), flavour intensity (P 00.005; 5.40 vs. 5.14), amount of connective tissue (P00.0002; 7.64 vs. 7.18), and overall tenderness (P00.003; 7.13 vs. 6.50). Only initial juiciness was significantly affected (P00.02) by the ossification group (5.38, 5.64 and 5.76). A gender )ossification group interaction was also detected for flavour intensity (P00.004) and off-flavour intensity (P00.03), but the magnitudes of the differences were in the order of one-half panel unit or less, generally below the detection of most consumers. The range of physiological maturity studied had limited effects on meat quality and support the elimination of an intermediate physiological maturity grade (51Á80% ossification) from the Canadian Bison Grading System. Lo´pez-Campos, Ó ., Aalhus, J. L., Galbraith, J., Larsen, I. L., Jua´rez, M., Uttaro, B. et Robertson, W. M. 2014. La relation entre la maturite´physiologique de la carcasse et la qualite´de la viande dans le syste`me de classement canadien du bison.Can. J. Anim. Sci. 94: 55Á62. Un total de 119 carcasses de bison, taureaux (n 062) et ge´nisses (n 057), ont e´te´se´lectionne´es pour de´terminer l'efficacite´de la gamme de maturite´(jeune a`interme´diaire) [ossification aux 9/10/11 ie`me apophyses e´pineuses thoraciques ( 550 %; 51Á65 %; 66Á80 %)] a`classer pre´cise´ment les carcasses de bison selon la qualite´. Les carcasses e´taient classe´es dans un de trois groupes de maturite´selon l'ossification aux 9/10/11 ie`me apophyses e´pineuses thoraciques (550 %; 51Á65 %; 66Á80 %). Il y a eu alors une collecte de donne´es sur la carcasse, la qualite´de la viande et les e´valuations sensorielles. Les carcasses de taureaux e´taient significativement (PB0,0001) plus lourdes que les carcasses de ge´nisses (308,0 c. 228,6 kg), tandis que les ge´nisses avaient des cotes de persillage plus e´leve´es (P B0,0001) que les ta...