International Journal of Poultry Science 14 (5): 257-261, 2015 ISSN 1682-8356 © Asian Network for Scientific Information, 2015 Corresponding Author: S.L. Vieira, Departamento de Zootecnia, Universidade Federal do Rio Grande do Sul, Avenida Bento Goncalves, 7712, Porto Alegre, RS, Brazil 257 Energy Utilization from Various Fat Sources by Broiler Chickens at Different Ages S.L. Vieira , L. Kindlein , C. Stefanello , C.T. Simoes, G.O. Santiago and L.P. Machado 1 2 1 3 Departamento de Zootecnia, Universidade Federal do Rio Grande do Sul, 1 Av. Bento Goncalves, 7712, Porto Alegre, RS, 91540-000, Brazil Departamento de Medicina Veterinaria Preventiva, Universidade Federal do Rio Grande do Sul, 2 Av. Bento Goncalves, 8834, Porto Alegre, RS, 91540-000, Brazil Alibem Comercial de Alimentos Ltda, Av. Protasio Alves, 3326, Porto Alegre, RS, 90410-007, Brazil 3 Abstract: Two studies were conducted to estimate nitrogen-corrected apparent metabolizable energy (AMEn) of different fat sources for broilers from 1 to 7 and 28 to 35 d of age. Corn-soybean meal diets with inclusions of 2, 4 and 8% degummed soybean oil (DSO), acidulated soybean soapstock (ASS), or pork lard (PL) (experiment 1) and coconut oil (CCO), palm oil (PO), or palm kernel oil (PKO) (experiment 2). Fats were added to the feeds at the expense of corn starch. Experiments were conducted in battery cages (0.72 m ) with 2 8 Ross × Ross 308 male broiler chicks each. Experimental diets were provided from 1 to 7 and 28 to 35 d and feed intake was recorded for each cage. Total excreta was collected from 3 to 7 and 33 to 35 d. Linear regressions at each age (Y = a + bx; Y = apparent available fat; x = level of fat added) allowed estimations of AMEn for each fat source as the product of the coefficient of apparent availability of fat (slope of the equations) multiplied by the gross energy of fat. Estimated values of AMEn (kcal/kg) from 1 to 7 vs. 28 to 35 d were, respectively, 8.348 vs. 9.283 (DSO); 7.706 vs. 8.533 (ASS); 8.219 vs. 8.781 (PL); 7.837 vs. 8.824 (CCO); 7.952 vs. 8.884 (PO) and 7.627 vs. 8.425 (PKO). Older chickens had average increases in fat AMEn of 8.3 and 10.5% compared to the younger ones. These responses present useful values for poultry feed formulation. Key words: Broiler, fat, metabolizable energy INTRODUCTION Fat is routinely added to broiler feeds, in varying amounts in order to increase energy concentration. The cost of dietary energy has been increasing as a result of a consistent expansion in the demand for vegetable fat sources worldwide, a trend that has been exacerbated in recent years with the rise in use of vegetable fats for biodiesel production. Use of alternative sources of lower costs has been hindered by limitation in the knowledge of their effective energy utilization by poultry. Several factors affect nitrogen-corrected apparent metabolizable energy (AMEn) values of fat for poultry, including type of fatty acid (chain length and degree of saturation) and rate of inclusion in feeds (Artman, 1964; Wiseman and Salvador, 1991). Fatty acid chain length is a chemical structural factor that has a direct impact on the AMEn of supplemental fats with fatty acids having longer chain lengths usually have higher AMEn values for poultry (NRC, 1994). On the other hand, unsaturated fatty acids are better utilized when compared to saturated ones in younger birds (Wiseman et al., 1986; Leeson and Atteh, 1995; Smits et al., 2000). However, significant effects of age on excreta fatty acids were found and the proportion of saturated fatty acids were greater in older than younger birds. Improvements in fat retention and metabolizable energy (ME) of fats with increasing age may be a reflection, in part, of an increase in absorption of the saturated fatty acids such as C16 and C18 (Sell et al., 1986). Fat absorption and subsequent AMEn value of saturated fats has been shown to increase when they are mixed with unsaturated fats (Renner and Hill, 1961; Wiseman and Lessire, 1987). In parallel, a higher efficiency of fat utilization has been related to the increase in dietary fat level (Carew and Hill, 1964; Wiseman and Salvador, 1989). Physiological functions necessary for the utilization of dietary fats are immature in birds during the first post-hatching days (Carew et al., 1972) and the limited availability of bile salts, lipase, colipase and phospholipids may reduce utilization of dietary lipids when birds were fed with higher dietary fat levels (Krogdahl, 1985; Escribano et al., 1988). Fat utilization in young poultry is lower than that of more mature birds. This in parts appears to be partly due to a poorer reabsorption of bile salts by younger birds which can impair the formation of fat micelles (Noy and Sklan, 1998; Smits et al., 2000). Lower lipase secretion has also been shown as a cause for the reduced fat utilization by young chicks (Leeson and Atteh, 1995) and the improvements in fat utilization noted with increasing