Effect of low vitamin A diets with high-moisture or dry corn on marbling and adipose tissue fatty acid composition of beef steers.
Angus-cross steers (n = 165; 295 +/- 16 kg of BW) were used evaluate the effect of low vitamin A diets with high-moisture corn (HMC) or dry corn (DC) on marbling and fatty acid composition. Steers were allotted to 24 pens (7 steers/pen), such that each pen had the same average initial BW. Treatments were randomly allotted to the pens. The experiment had a completely randomized design, with a 2 x 2 factorial arrangement of treatments: low vitamin A (Lo, no supplemental vitamin A) and HMC (LoHMC); LoDC; high vitamin A (Hi, supplemented with 2,200 IU of vitamin A/kg of DM) and HMC (HiHMC); and HiDC. Diets contained 76% corn, 10% corn silage, 11% protein supplement, and 3% soybean oil (DM basis). Samples of feed ingredients were collected for carotenoid analysis. Blood samples were collected for serum retinol determination. Steers were slaughtered after 145 d on feed. Carcass characteristics and LM composition were determined. Samples from the s.c. fat depot were analyzed for fatty acid composition. High-moisture corn had a greater vitamin A content, based on its carotenoid content, than DC (614 vs. 366 IU/kg of DM, P < 0.01). No vitamin A x corn type interactions were detected for feedlot performance, carcass characteristics, or serum, s.c. fat, or liver retinol concentration. Average daily gain, DMI, and G:F were not affected by vitamin A (P > 0.05). Marbling score and USDA quality grade were greater (P < 0.05) in Lo vs. Hi steers. Hot carcass weight, backfat, and yield grade were not affected by the treatments (P > 0.05). Vitamin A and corn type did not affect LM composition (DM, ash, CP, or ether-extractable fat, P > 0.05). Vitamin A supplementation increased (P < 0.06) serum retinol on d 112 and 145 and increased (P < 0.01) liver retinol at slaughter (Lo = 38.7 vs. Hi = 102.9 mug/g). The s.c. fat retinol concentrations were less (P < 0.01) for Lo (0.8 mug/g) than for Hi (1.4 mug/g) at slaughter. Cell diameter of adipocytes in the i.m. depot was not affected by dietary vitamin A (P > 0.05). A vitamin A x corn type interaction was observed (P < 0.05) for the s.c. fat cellularity. Feeding HMC increased the number of cells per square millimeter when Lo diets were fed (LoHMC = 128 vs. LoDC = 100 cells/mm(2), P < 0.05), but not when Hi diets were fed (HiHMC = 109 vs. HiDC = 111 cells/mm(2), P > 0.05). The CLA content of adipose tissue was not affected by the treatments. Regardless of the corn type used, feeding low vitamin A diets for 145 d to Angus-cross steers increased marbling and quality grade without affecting yield grade, animal health, or performance.
Gorocica-Buenfil
M A
MA
Department of Animal Sciences, The Ohio State University, Wooster 44691, USA.
Fluharty
F L
FL
Bohn
T
T
Schwartz
S J
SJ
Loerch
S C
SC
D017667:Adipocytes / Q000166:cytology; D000273:Adipose Tissue / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001823:Body Composition / Q000187:drug effects* / Q000502:physiology; D002417:Cattle / Q000254:growth & development* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005227:Fatty Acids / Q000032:analysis / Q000378:metabolism; D008297:Male; D008460:Meat / Q000592:standards; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism; D011897:Random Allocation; D014801:Vitamin A / Q000494:pharmacology*; D014815:Vitamins / Q000494:pharmacology; D015430:Weight Gain / Q000187:drug effects*; D003313:Zea mays
D005227:Fatty Acids; D014815:Vitamins; D014801:Vitamin A