The effect of particle size and energy levels on broiler performance from 23 to 42 days of age

Feeding is the most important cost factor impacting poultry production. Studies have been carried out in the search of technologies to increase the efficiency and quality of poultry feeds, such as determining nutrient levels for each life stage, alteration of the physical form of the feed through processing, and defining ideal ingredient particle sizes.

In the search of improving pellet quality, nutritionists need to associate the grinding level of grains with increased grinder performance and reduced power usage in the feed mill. Fat needs to be added to the rations due to the high energy demand of broilers. These factors are directly related with pellet quality, since finer particle sizes result in improved pellet quality and increased power expense. Using coarser particle sizes results in reduced milling expenses but pellet quality is adversely affected. Oil inclusion level in broiler rations can also have a negative impact on pellet quality. Therefore, the purpose o this study was to evaluate the effects of different particle sizes and energy levels in pelleted rations on the performance of growing broilers, from 23 to 42 days of age.

Seven hundred and twenty (720) Ross male broilers weighing 1,075±0.033 kg, were housed at a density of 9.6 birds/m². One single ration was given to these animals up to 22 days of age then birds were allocated to their treatment groups. Water and feed were provided ad libitum.

Birds were placed in a brickwork, open-sided house partitioned into 10 m² pens, with wood s litter. The equipment and management practices were similar to those used in commercial broiler farms.

The only difference between the two rations was the energy value. The composition and nutritional values of these diets are shown in Table 1. For ration formulation, the nutritional values in Brazilian Tables for Poultry and Swine (Tabelas Brasileiras de Aves e Suínos, Rostagno et al.,)( 2005) were used. Dietary nutritional levels were established in agreement with Lara et al. (2008a). Corn particle sizes were determined using 3 different screens (fine, <1.0 mm; medium, 2.5 mm; coarse, 6.0 mm.)

Treatments considered both corn particle size and dietary energy levels, as follows: fine particles +   3,100 kcal/kg ME (oil inclusion, 2%); fine particles + 3,200 kcal/kg ME (oil inclusion, 4%); medium particles + 3,100 kcal/kg ME (oil inclusion, 2%); medium particles + 3,200 kcal/kg ME (oil inclusion, 4%); coarse particles + 3,100 kcal/kg ME (oil inclusion, 2%); coarse particles + 3,200 kcal/kg ME (oil inclusion, 4%.)

At 42 days of age, weight gain (WG), feed intake (FI), feed conversion rate (FCR) livability (Liv), energy intake (EI), and energy conversion rate (ECR) were determined.

A completely-at-random, 3 x 2 factorial (3 particle sizes x two energy levels) experimental design was used for a total of 6 treatments with five repetitions of 24 birds each. Results were subjected to analysis of variance, and the means were compared using Tukey''''s test in the SAEG software (2007.)

Broiler performance results from 23 to 42 days of age are shown in Table 2.

No interaction (P>0.05) was found among energy levels and ingredient particle size, for any of the variables studied.

Table 2. Per-treatment weight gain (WG), feed intake (FI), feed conversion rate (FCR), livability (Liv), energy intake (EI) and energy conversion rate (ECR) of broilers from 23 to 42 days of age

Regardless of energy levels, particle size had no effect (P>0.05) on weight gain. Regardless of particle size, weight gain was increased (P≤0.05) with increased dietary energy levels. In accordance with Andreotti et al. (2004), this effect can be related with the high growth rate of broilers and with the increased oil intake in broilers at this stage. This increased weight gain with increased energy levels (higher oil inclusion rates in the diet) can also be related with the extra-caloric effects of oil.

No effects (P>0.05) of both particle size and energy level were found on FI or FCR. Results were similar to those reported by López y Baião (2004). Likewise, Nir et al. (1995) and Amerah et al. (2007) did not find an affect of feedstuff particle size in pelleted rations on FI due to increased feed waste at eating time, and increased energy expense at eating due to feed processing. As far as energy levels are concerned, Leeson et al. (1996) and Lara et al. (2008b) reported decreased feed intake as dietary energy levels increased, which shows the ability of the birds to self regulate feed intake. This result was opposite to our findings reported herein.

Regardless of energy levels, the medium particle size resulted in increased (P≤0.05) broiler livability when compared with fine particle size. Coarse particle size had an intermediate result and it was similar (P>0.05) to the other two particle sizes with regard to this variable. Results in this experiment disagree with those reported by López and Baião (2004), who found lower livability in broilers fed a ration with intermediate particle size when compared with those receiving coarse particle size feeds. Nevertheless, in this experiment, fine particle size resulted in improved livability when compared with intermediate particle size. As reported by Nir (1998), when the feed is finely ground, passage from the gizzard to the duodenum was faster, resulting in increased intestinal load and higher chyme levels in the small intestine, therefore increased oxygen demands, which can trigger a higher incidence of metabolic diseases such as ascites.

Regardless of particle size, the broilers fed higher energy levels had higher (P≤0.05) livability from 23 to 42 days of age when compared with those fed lower dietary energy levels. These results differ from those reported by Lecznieski et al. (2001) and Mendes et al. (2004.)

Regardless of energy levels, no influence (P>0.05) was found of ingredient particle size on energy intake. Regardless of particle size, an effect was found (P≤0.05) of dietary energy levels on broiler energy intake at 42 days of age, with higher energy intakes for higher energy levels (3,200 kcal/kg ME). Similar to our findings, Meinerz et al. (2001) and Lara et al. (2008b) found higher energy intakes with increased dietary energy levels. This is due to similar feed intakes in the face of different energy levels in each ration. The difference in energy intake with different dietary levels shows that boilers in the growing phase were not efficient in regulating their intake in the face of different dietary energy levels. This result is opposite to that reported by Meinerz et al. (2001), who observed efficiency in birds at regulating their intake, particularly when fed pelleted diets.

ECR from 23 to 42 days of age was not influenced (P>0.05) by either energy levels or particle sizes. This result agrees with Lecznieski et al. (2001).

Rations with 3,200 kcal/kg ME, regardless of particle size, results in enhanced broiler performance during the growing phase.

Amerah AM, Ravindran V, Lentle RG, Thomas DG. 2007. Influence of feed particle size and feed form on the performance, energy utilization, digestive tract development and digesta parameters of broiler starters. Poultry Science 86:2615-2623.

Andreotti M, Junqueira O, Barbosa M, Cancherini L, Araújo L, Rodrigues E. 2004. Energia metabolizável do óleo de soja em diferentes níveis de inclusão para frangos de corte nas fases de crescimento e final. Revista da Sociedade Brasileira de Zootecnia 33(5):1145-1151.

Lara LJC, Baião NC, Rocha JSR, Lana AMQ, Cançado SV, Fontes DO, Leite RS. 2008a. Influência da forma física da ração e da linhagem sobre o desempenho e rendimento de cortes de frangos de corte. Arquivos Brasileiros de Medicina Veterinária e Zootecnia, v.60, n.4, p.970-978.

Lara, JCL, Teixeira JL, Baião NC, Cançado SV, Rocha JSR, Michell BC. 2008b. Efeito dos níveis de energia da dieta sobre o desempenho e rendimentos de carcaça de frangos de corte. Revista Ceres 55:402-408.

Lecznieski JL, Ribeiro AML, Kessler AM, Penz Jr AM. 2001. Influência da forma física e do nível de energia da ração no desempenho e na composição de frangos de corte. Arch. Latinoam. Prod. Anim. 9(1):6-11.

Leeson S, Caston L, Summers JD. 1996. Broiler response to diet energy. Poultry Science 75:529-535.

Lopez CAA & Baião NC. 2004. Efeitos do tamanho da partícula e da forma física da ração sobre o desempenho, rendimento de carcaça e peso dos órgãos digestivos frangos de corte. Arquivos Brasileiros de Medicina Veterinária e Zootecnia 56(2):214-221.

Meinerz V, Ribeiro AML, Penz Jr AM, Kessler AM. 2001. Níveis de energia e peletização no desempenho e rendimento de carcaça de frangos de corte com oferta alimentar equalizada. Ver. Bras. Zootec. 30(6S):2026-2032.

Mendes AA, Moreira J, Oliveira EG, Garcia EA, Almeida MIM, Garcia RG. 2004. Efeitos da energia da dieta sobre o desempenho, rendimento de carcaça e gordura abdominal de frangos de corte. Revista Brasileira de Zootecnia 33(6):2300-2307, supl.3.

NIR I. 1998. Resposta de frangos de corte à estrutura alimentar: ingestão de alimentos e trato gastrointestinal, pp. 49-68. In: Simpósio Internacional sobre Nutrição de Aves, Campinas. Anais. Campinas:CBNA.

Nir I, Hillel R, Ptichi I, Shefet G. 1995. Effect of particle size on performance. 3. Grinding pelleting interactions. Poultry Science 74:771-783.

Rostagno HS, Albino LFT, Donzele JL et al. 2005. Tabelas Brasileiras para Aves e Suínos - composição de alimentos e exigências nutricionais. Viçosa: UFV/Departamento de Zootecnia, 186p.

Universidade Federal De Viçosa - UFV. 2007. SAEG - Sistemas de análises estatísticas e genéticas. Versão 9.1. Viçosa/MG.