Effects of time on feed on beef nutrient composition.
Forty-eight Angus x Hereford yearling steers were used to assess the effect of time on feed (TOF) on the nutrient composition of beef longissimus muscle (LM). Steers were fed a high-concentrate diet with the exception of the d-0 group, which served as a grass-fed control, and then were serially slaughtered at 28-d intervals during the 196-d feeding period. Steaks were removed from the 10th rib and trimmed of exterior fat and epimysial connective tissue before nutrient analysis. Intramuscular fat content doubled (P < .05) between d 84 and 112 but did not differ (P > .05) from d 0 to 84 or from d 112 to 196. This increase in fat content resulted in decreased (P < .05) concentrations of moisture, protein, and ash in the LM. Concentrations of Mg, K, and Fe in the LM increased (P < .10) with advanced TOF. The increase in the total lipid (TL) content of the LM stemmed from a proportional increase (P < .05) in neutral lipid (NL). Polar lipid (PL) remained constant (P = .33) throughout TOF. The NL and TL became more unsaturated as TOF increased, primarily due to a linear (P < .01) increase in oleic (C18:1) acid concentration. In contrast, the polyunsaturated fatty acid (PUFA) concentration in the PL exhibited a linear (P < .01) decrease across TOF. As a result, advanced TOF increased the monounsaturated fatty acid (MUFA) content by 22% and decreased the PUFA content by 72% in the LM. The ratio of hypercholesterolemic (C14 + C16):hypocholesterolemic (MUFA+PUFA) fatty acids was unaffected by increasing TOF from d 28 to 196; however, this ratio was lower (P < .05) for grass-fed controls (d 0) than for d 28 to 84 and d 196. Cholesterol content (milligrams/100 grams) changed cubically (P = .06) across TOF. Ultimately, by limiting TOF to 112 d, the beef industry could provide consumers a palatable beef product that easily fits into a healthy diet and at the same time diminishes the costs associated with external fat trim.
Duckett
S K
SK
Department of Animal Science, Oklahoma State University, Stillwater 74078-0425.
Wagner
D G
DG
Yates
L D
LD
Dolezal
H G
HG
May
S G
SG
D000818:Animals; D002417:Cattle / Q000254:growth & development*; D002784:Cholesterol / Q000032:analysis; D005227:Fatty Acids / Q000032:analysis; D008055:Lipids / Q000032:analysis / Q000737:chemistry; D008297:Male; D008460:Meat / Q000592:standards*; D008903:Minerals / Q000032:analysis; D009132:Muscles / Q000737:chemistry*; D009753:Nutritive Value; D013997:Time Factors
D005227:Fatty Acids; D008055:Lipids; D008903:Minerals; D002784:Cholesterol