Modification of muscle inherent properties through age at slaughter, growth promotants and breed crosses

Abstract

. 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.

Contribution of myofibrillar and connective tissue components to the Warner–Bratzler shear force of cooked beef

“…In the ST, both MF-SF and CT-SF mean values increased with age at slaughter, with the increase in mean CT-SF value corroborating a previously observed trend for soluble collagen to decrease with age at slaughter in the same steers (Girard et al, 2011). Also in the ST, IMP increased only the mean CT-SF value, suggesting that connective tissue was responsible for the increase in peak SF observed in the ST with IMP (Girard et al, 2012).…”

“…Pearson correlations (PROC CORR; SAS Version 9.2, SAS Institute Inc., Cary, NC) were used to test for linear relationships between maximum MF-SF, CT-SF, and peak SF and the inherent properties and meat quality characteristics measured as described by Girard et al (2011Girard et al ( , 2012, respectively. Twenty-six comparisons were made per SF, so a Bonferroni correction was used to correct the α significance value (26 comparisons for each SF, α = (0.05/26)) and the correlations were significant at P b 0.002.…”

“…Muscles were individually labelled and steaks were removed from the proximal to distal ends for the ST and from the anterior to posterior end for the GM. The first trim steak was discarded and the second 2.5 cm thick steak was used for muscle fibre type determination (Girard et al, 2011), 24 h objective colour and sarcomere length (Girard et al, 2012). Following 7 days ageing at 4°C, one 2.5 cm thick steak was cut from each muscle.…”

“…Inherent muscle characteristics (muscle fibre type, total and soluble collagen and proximate analyses) and meat quality (L*, a*, b*, myoglobin relative contents, purge loss, cooking loss, cooking time, sarcomere length and Warner-Bratzler shear force) data were originally presented by Girard et al (2011) and Girard et al (2012), respectively, and these data were used to investigate relationships between muscle properties, meat quality and the putative myofibrillar and connective tissue portions of the Warner-Bratzler shear force deformation curve. Data records from 112 crossbred Hereford-Aberdeen Angus (HAA; n =64) or Charolais-Red Angus (CRA; n = 48) that were part of a 2 × 2 × 2 factorial experiment that examined the effect of production practice on beef meat quality were used.…”

“…Warner-Bratzler shear force and meat quality data were from a study described by Girard, Aalhus, Basarab, Larsen and Bruce (2011) and Girard, Aalhus, Basarab, Larsen and Bruce (2012). Inherent muscle characteristics (muscle fibre type, total and soluble collagen and proximate analyses) and meat quality (L*, a*, b*, myoglobin relative contents, purge loss, cooking loss, cooking time, sarcomere length and Warner-Bratzler shear force) data were originally presented by Girard et al (2011) and Girard et al (2012), respectively, and these data were used to investigate relationships between muscle properties, meat quality and the putative myofibrillar and connective tissue portions of the Warner-Bratzler shear force deformation curve.…”