Authors : D.K. Lunt , K.Y. Chung , C.B. Choi and S.B. Smith
Abstract: We hypothesized that carcass and fatty acid composition of Angus and Japanese Black (Wagyu) steers would not differ if the steers were fed to a typical US. final weight, but that Wagyu steers fed to a typical Japanese endpoint body weight would have greater quality grades and softer fat than Angus steers. Sixteen Angus and 16 Wagyu 8-months-old, weaned steers were assigned to a corn-based diet for 8 or 16 months (n = 4 per breed type and time) or hay-based diet for 12 or 20 months (n = 4 per breed type and time) in a 2 x 2 factorial arrangement. Average daily gain was greater in Angus steers than in Wagyu steers, due primarily to the initially high ADG in corn-fed Angus steers. Marbling scores and USDA quality grades were not different between breed types (p= 0.31), but were higher in corn-fed steers than in hay-fed steers. USDA yield grade was greater at the Japanese endpoint than at the US. endpoint, but only in Angus steers (breed x endpoint interaction (p=0.03). There also was a significant (p= 0.05) breed x endpoint interaction for 12 rib th M. longissimus thoracis intramuscular lipid concentration; intramuscular lipid continued to increase to over 20% in the Wagyu steers, but attained a plateau (14.7%) by 16 months on feed in the Angus steers. These results confirm that Wagyu cattle must be raised to greater physiological maturity before they differ from Angus cattle in M. longissimus thoracis intramuscular lipid concentration. Subcutaneous adipose tissue concentrations of oleic (18:1n-9), 18:2n-6, 18:3n-3 and 18:2trans-0,cis-12 conjugated linoleic acid all were greater in Wagyu steers than in Angus steers (p= 0.05). All monthsnounsaturated fatty acids increased between the US. and Japanese endpoint, whereas slip points of lipids in s.c. adipose tissue were 10?C lower in Japanese endpoint steers than in US. endpoint steers (p= 0.01). Angus adipose tissue exhibited peak SCD enzyme activity at 16 months (corn-based diet) but activity in Wagyu adipose tissue was greatest at 20 months (hay-based diet) (breed x diet x endpoint interaction p= 0.08). However, SCD gene expression in Angus adipose tissue was maximal at 12 months (hay diet), whereas Wagyu adipose tissue had peak expression at 16 months (corn diet) (p<0.03). Breed type, diet and slaughter endpoint all collectively contribute to the observed adipose tissue compositional differences between Wagyu and typical US. breed types.
D.K. Lunt , K.Y. Chung , C.B. Choi and S.B. Smith , 2005. Production Characteristics and Carcass Quality of Angus and Wagyu Steers Fed to US and Japanese Endpoints . Journal of Animal and Veterinary Advances, 4: 949-953.