title: The effects of animal age, feeding regime and a dietary beta-agonist on tenderness of three beef muscles.
abstract: BACKGROUND
  Animal age as determined by number of permanent incisors (p. i.) is used in classification of beef carcasses to describe expected meat tenderness. However, animals differing in age are reared under different production systems (pasture or feedlot). In addition to age, other factors associated with particular production systems may also influence the palatability of meat. Therefore, the effects of age combined with feeding regime and the supplementation of a beta-agonist (zilpaterol) on the tenderness of M. longissimus lumborum (LL), M. semitendinosus (ST) and M. biceps femoris (BF) muscles were investigated.
  
  
  RESULTS
  Tenderness of LL cuts was least affected by age but zilpaterol significantly decreased tenderness and ageing potential. Tenderness of high-collagen cuts (BF and ST) was negatively affected by age due to reduced collagen solubility. The effect of zilpaterol on these cuts was less significant and BF and ST cuts of the grain-fed A-age animals (0 p. i.) supplemented with zilpaterol (AZ) were more tender than the same cuts of grass-fed animals with 1-2 p. i. (AB-age) and grass-fed animals with 3-6 p. i. (B-age) according to Warner-Bratzler shear force (WBSF) and sensory analysis for tenderness.
  
  
  CONCLUSIONS
  This study indicates that beta-agonists may influence variation in tenderness within an age class more than age or feeding regime. © 2016 Society of Chemical Industry.
authors.affiliation: Animal Production Institute, Agricultural Research Council, Irene, South Africa.
authors.forename: Ennet
authors.initials: E
authors.lastname: Moholisa
authors.affiliation: Department of Microbial, Biochemical and Food Biotechnology, University of the Free State, Bloemfontein, South Africa.
authors.forename: Arno
authors.initials: A
authors.lastname: Hugo
authors.affiliation: Animal Production Institute, Agricultural Research Council, Irene, South Africa.|Department of Animal Sciences, Stellenbosch University, Stellenbosch, 7602, South Africa.
authors.forename: Phillip E
authors.initials: PE
authors.lastname: Strydom
authors.affiliation: Animal Production Institute, Agricultural Research Council, Irene, South Africa.
authors.forename: Ina
authors.initials: I
authors.lastname: van Heerden
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000367:Age Factors; D000818:Animals; D001823:Body Composition; D002417:Cattle; D003094:Collagen / Q000737:chemistry; D019587:Dietary Supplements; D018482:Muscle, Skeletal / Q000737:chemistry / Q000187:drug effects*; D000069466:Red Meat / Q000592:standards*; D014297:Trimethylsilyl Compounds / Q000494:pharmacology*
chemical_list: D000318:Adrenergic beta-Agonists; D014297:Trimethylsilyl Compounds; C475840:Zilpaterol; D003094:Collagen
keywords: animal age; beef tenderness; grain; grass; zilpaterol