The Influence of Free Fatty Acid Content and Degree of Saturation on the Apparent Metabolizable Energy Value of Fats Fed to Broilers

Abstract

To determine the influence of free fatty acid (FFA) content on the subsequent nutritive value of fats, the following were studied: tallow (FFA content of 138.4 g/kg) and tallow acid oil (FFA = 952.1 g/kg) in Experiment 1; palm oil (FFA = 57.5 g/kg) and palm acid oil (FFA = 917.5 g/kg) in Experiment 2; and soybean oil (FFA = 14.4 g/kg) and soybean acid oil (FFA = 683.4 g/kg) in Experiment 3. The two fats within each experiment were blended in proportions to give three mixtures of intermediary FFA content. Thus, each experiment investigated five fats by substituting them into a basal diet at the expense of the energy-yielding ingredients at rates of 40, 80, and 120 g/kg. Experimental diets were evaluated for apparent fat availability (AFA) of broiler chicks 1.5 and 7.5 wk of age. Corresponding values for fats were obtained through extrapolation of the linear response, or interpolation of the quadratic response, of AFA of diets. The AME was calculated as the product of fat AFA and gross energy. The degree of saturation had a pronounced effect upon the AME of fats; values decreased in the following order: soybean oil, tallow, and palm oil. Overall AME of fats linearly decreased with increasing FFA content, and the decrease was more pronounced with the younger birds. This rate of reduction appeared to be influenced by degree of saturation of the fat, but only with younger birds. Thus, AME of fats declined from 30.9 to 20.4, 27.7 to 14.8, and 38.5 to 33.1 MJ/kg (1 MJ = .239 Mcal) for young birds in Experiments 1, 2, and 3, respectively. Corresponding data for older birds were from 32.9 to 28.3, 32.3 to 27.5, and 38.5 to 35.1 MJ/kg. Effects of rate of inclusion of fats were minor and, generally, were confined to fats of a higher degree of saturation with greater contents of FFA evaluated with younger birds.

Utilization of Crude Glycerin in Nonruminants

“…The reduced ability of broilers to efficiently utilize glycerin co-products having relatively high free fatty acid content as indicated by their lower ME:GE ratio warrants additional discussion. Wiseman and Salvador (1991) reported a linear reduction of ME content in broiler diets containing increasing concentrations of free fatty acids, which was supported by others (Artman, 1964;Sklan, 1979) who reported that free fatty acids reduce the rate of absorption compared with lipid sources containing triglycerides and free fatty acids. This reduced absorption in products containing free fatty acids may be partially due to the absence of a monoglyceride backbone to aid absorption because the relatively low concentration of monoglycerides in the duodenum, which may depress the amount of fatty acids entering micellular solution.…”

Efeito do processamento da soja integral sobre a energia metabolizável e a digestibilidade dos aminoácidos para aves

“…No método tradicional com pintos, o menor CDEEA do FSOA, em relação ao da SIE e do FSO, pode ser atribuído à composição em ácidos graxos do óleo ácido de soja, que é composto, basicamente, por ácidos graxos livres. O aumento da quantidade de ácidos graxos livres em uma fonte de gordura reduz a digestibilidade e a absorção dessa gordura (Wiseman & Salvador, 1991;Vilá & Esteve-Garcia, 1996). Segundo Sklan (1979), a absorção de gordura pelas aves é precedida do rompimento (digestão) dos triglicerídeos e favorecida pela presença de monoglicerídeos resultantes desse rompimento, que ativam a secreção de bile, necessária para a formação das micelas, e a presença de ácidos graxos livres dificulta esses processos.…”

Valor energético de algumas fontes lipídicas determinado com frangos de corte

“…Entretanto, a avaliação das verdadeiras contribuições energéticas das gorduras é extremamente difícil, pois envolve fatores não necessariamente associados às suas qualidades, como concentração de energia ou de gorduras e proteína na ração, idade e espécie das aves, níveis de inclusão, fontes de fibras na ração, taxa de passagem do alimento pelo sistema digestório e métodos de determinação (Rao & Clandinin, 1970;Kass et al, 1980;Mateos & Sell, 1981;Wiseman & Salvador, 1989;Wiseman & Salvador, 1991). Além desses fatores não necessariamente ligados à qualidade, o comprimento da cadeia de ácidos graxos, o grau de saturação, a quantidade de ácidos graxos livres e o conteúdo de ácido linoléico (Mateos & Sell, 1980;Nitsan et al, 1997) alteram os valores de energia metabolizável, em razão dos mecanismos de digestão e absorção das gorduras (Wiseman & Salvador, 1991).…”