Effects of time on feed on beef nutrient composition

Abstract

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.

Effects of pre-weaning concentrate feeding on calf performance, carcass and meat quality of autumn-born bull calves weaned at 90 or 150 days of age

“…Previous experiments on age at weaning or pre-weaning concentrate feeding did not study meat fatty acid profile, which depends mainly on the composition of the diet given to the animals. Indeed, no differences were evident in the current experiment, because calves received the same intensive feeding for 123 to 225 days, a period long enough for previous SFA, PUFA and MUFA differences to vanish (Duckett et al, 1993).…”

Environmental effects on the fatty acid composition of subcutaneous beef fat

“…Duckett et al 1993;Camfield et al 1997) and finishing regime (e.g. Mandell et al 1998) on fatty acid composition; although these studies have been restricted to animals raised in 1 environment.…”

Perfil de ácidos graxos na carne de novilhos superjovens da raça Devon, terminados sob diferentes sistemas de alimentação

“…Dos ácidos graxos saturados de maior importância para a saúde humana, os ácidos mirístico (C14:0), palmítico (C16:0) e esteárico (18:0) não foram influenciados pela dieta (Tabela 3). Dentre estes, os ácidos mirístico e palmítico são considerados hipercolesterolêmicos (ARRIGONI et al, 2007) É possível que a contradição dos resultados do presente estudo com a literatura deve-se, em parte, pelo curto período de terminação dos animais, principalmente os confinados (47 dias), uma vez que Duckett et al (1993) observaram que o tempo de alimentação interferiu na composição dos ácidos graxos. Estes autores somente observaram aumentos na participação dos ácidos mirístico, palmítico e esteárico após 112; 28 e 140 dias de alimentação, respectivamente.…”

“…Por outro lado, Gatellier et al (2005) não observaram diferença no teor de AGM na gordura intramuscular de bovinos terminados exclusivamente em pastagens ou em dietas com participação de concentrado. Acréscimos no teor de AGM são associados a aumentos na participação de gordura da carcaça (DUCKETT et al, 1993). No presente estudo, as carcaças dos animais da pastagem tropical apresentaram menor espessura de gordura subcutânea (3,20; 4,31 e 4,38 mm para pastagem tropical, confinamento e pastagem temperada, respectivamente), refletindo essa resposta na quantidade de lipídios totais na carne (Tabela 3).…”

“…No entanto, a quantidade de concentrado empregada no presente estudo (40%) pareceu não influenciar essa característica, concordando com o observado por Varela et al (2004). Outra possível explicação para a falta de diferença seria o baixo tempo de alimentação para os animais do confinamento (47 dias), pois, segundo Duckett et al (1993), o perfil de AGP se modificará apenas após 112 dias de arraçoamento.…”