Effect of dietary vitamin A concentration and roasted soybean inclusion on marbling, adipose cellularity, and fatty acid composition of beef

• Published in: Journal of animal science 2007-09, Vol.85 (9), p.2230-2242
• Main Authors: Gorocica-Buenfil, M. A, Fluharty, F. L, Reynolds, C. K, Loerch, S. C
• Format: Article
• Language: English
• Subjects: Adipocytes - cytology; Adipose Tissue - chemistry; Adipose Tissue - metabolism; Animal Feed; Animal Nutritional Physiological Phenomena; Animal productions; Animals; Beef; Biological and medical sciences; Body Composition - drug effects; Body Composition - physiology; Cattle - growth & development; Cattle - metabolism; Diet; Dose-Response Relationship, Drug; Fatty acids; Fatty Acids - analysis; Fatty Acids - metabolism; Food industries; Fundamental and applied biological sciences. Psychology; Glycine max; Male; Meat - analysis; Meat - standards; Meat and meat product industries; Muscle, Skeletal - chemistry; Muscle, Skeletal - metabolism; Random Allocation; Soybeans; Terrestrial animal productions; Vertebrates; Vitamin A; Vitamin A - administration & dosage; Vitamin A - blood; Vitamins - administration & dosage; Vitamins - blood; Weight Gain - drug effects; Weight Gain - physiology
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas.2006-780

A feedlot trial was conducted to determine the effect of dietary vitamin A concentration and roasted soybean (SB) inclusion on carcass characteristics, adipose tissue cellularity, and muscle fatty acid composition. Angus-crossbred steers (n = 168; 295 +/- 1.8 kg) were allotted to 24 pens (7 steers each). Four treatments, in a 2 x 2 factorial arrangement, were investigated: no supplemental vitamin A, no roasted soybeans (NANS); no vitamin A, roasted SB (20% of the diet on a DM basis; NASB); with supplemental (2,700 IU/kg) vitamin A, no roasted SB (WANS); and with supplemental vitamin A, roasted SB (WASB). Diets included high moisture corn, 5% corn silage, 10 to 20% supplement, and 20% roasted SB in the SB treatments on a DM basis. The calculated vitamin A concentration in the basal diet was < 1,300 IU/kg of DM. Blood samples (2 steers/pen) were collected for serum vitamin A determination. Steers were slaughtered after 168 d on feed. Carcass characteristics and LM composition were determined. Fatty acid composition of LM was analyzed, and adipose cellularity in the i.m. and s.c. depots was determined. No vitamin A x SB interactions were detected (P > 0.10) for cattle performance, carcass composition, or muscle fatty acid composition. Low vitamin A diets (NA) did not affect (P > 0.05) ADG, DMI, or G:F. Quality grade tended (P = 0.07) to be greater in NA steers. Marbling scores and the percentage of carcasses grading > or = Choice(-) were 10% greater for NA steers, although these trends were not significant (P = 0.11 and 0.13, respectively). Backfat thickness and yield grade were not affected (P > 0.26) by vitamin A supplementation. Composition of the LM was not affected (P > 0.15) by vitamin A or SB supplementation. Serum retinol at slaughter was 44% lower (P < 0.01) for steers fed NA than for steers supplemented with vitamin A (23.0 vs. 41.1 microg/dL). A vitamin A x SB interaction occurred (P < 0.05) for adipose cellularity in the i.m. depot; when no SB was fed, vitamin A supplementation decreased cell density and increased cell size. However, when SB was fed, vitamin A supplementation did not affect adipose cellularity. Adipose cellularity at the s.c. depot was not affected (P > 0.18) by vitamin A or SB treatments. Fatty acid profile of the LM was not affected by vitamin A (P > 0.05), but SB increased (P < 0.05) PUFA (7.88 vs. 4.30 g/100 g). It was concluded that feeding NA tended to increase marbling without affecting back-fat and yield grade. It appeared