Effect of the use of a preservative liquid premix in pelletized feed for broilers on the quality and nutritional value of the final product

Various authors (Moritz et al., 2002;) Hott et al., 2008) have shown that the addition of moisture to pelletized feed significantly increases production yields and reduces energy consumption, without altering the quality of neither the pellet nor the durability and the production of fine pellets. However, the effects of that moisture in such sensitive parameters for quality as microbial contamination or pellet hardness have not been sufficiently explored. With regular use of the tested product (Rehydra-Pro^®), thanks to its surfactant content (max 10%), which allows a dispersion of fat in water, thus lubricating the feed mass to pellets, gains in production yield (tons/h) of 4-10% have been observed, as well as a decrease in power consumption of 8-10% in engine amperage, lower costs for water vapor in the air condition, less output of fine pellets, improvement in the recovery of waste (own data, average of 20 trials). But, in addition to this, its content of pure organic acids (propionic acid; max 60%) produces a shock effect and a residual effect (long term release) due to its ammonic salts (max. 27 %), thus achieving optimal microbiological control along with improvements in other quality parameters such as the durability and hardness of the pellets. Furthermore, the formulation of the feed, depending on the levels of protein, fiber, and fat modifies the quality of the pellets (Buchanan & Moritz, 2009; Buchanan et al., 2010). All commented quality parameters affect the voluntary intake and digestibility of nutrients, which has an impact on the productive performance of animals (Moritz et al., 2002; Hott et al., 2008). Therefore, it is necessary to carry out a detailed study on effects of the use of 2% Rehydra-Pro^® (400 ppm) in pelletized feeds for fattening broiler chickens with two types of formulas on the quality of the pellets and the nutritional value of the resulting feed.

Two formulations of feed for chickens for fattening broiler chicken in the stage of growth were prepared (FEDNA, 2008): Diet 1, based on maize (maize: 51%; soy flour-48%CP: 26%; extruded soy: 16%; grease 3/5: 3,4%; Rest up to 100%: amino acids, vitamins, minerals and salt), and Diet 2, based on white cereal (wheat: 34%; barley:18,4%; soy flour-48CP: 23%; extruded soy: 16%; grease 3/5: 5.5%; Rest up to 100%: amino acids, vitamins, minerals and salt).

For each diet, three treatments were established: C, control-base diet treatment, A, treatment C with 2% water, RHP, treatment C with the addition of 2% of Rehydra-Pro^® (400ppm) hydrating solution .

Production runs took place from November 11 - 13, 2009 at the IRTA-Nutrition Monogastrics Experimental Feed Mill (Tarragona, Spain). Feed was milled to 3 mm, and pellet size was 2.5 mm. In Diet 1, all the grease was added in the mixer. In Diet 2, 3.4% was added in the mixer and 2.1% was added post-pellet. Water and Rehydra-Pro^® were sprayed in the mixer and mixing time after addition was 2 min. Since we did not wish to study the effect of the use of the additive on the production parameters, but the effect thereof on the quality and nutritional value of the feed, fixed production and granulation conditions were used for all treatments (manufacturing process time: 26 min, granulation temperature: 70 ºC, steam pressure: 2.5 kg/cm²), in order to assure that the results were a direct consequence of treatment, and not an indirect result of the effect of the differences of treatment on the production parameters. No granulation aids were used. For each treatment a 350 kg mixture was produced and pelletized.

15 subsamples of each treatment were taken out of the cooler during the packing process and, after mix homogenization; samples were taken in self-sealing, air-tight bags for the following determinations:

Since there was only one production run for each treatment, no statistical analysis of results was performed.

The most significant results concerning the microbiological quality are shown in table 1. The high microbiological quality in Diet 1 on day 0, was maintained at 15 days in C (absence of Salmonella/25 g, < 10 cfu/g of E. coli, < 200 cfu/g enterobacteria < 400 cfu/g fungi; < 10 cfu/g Clostridium perfringens). On the other hand, with the increase of humidity in A there was an increase in the content of enterobacteria and fungi. Whereas the addition of 2% of RHP (400 ppm), even with the same increase in humidity as in A, was able to maintain the content of enterobacteria and reduce the presence of fungi. The initial microbiological quality of Diet 2 was worse than that of Diet 1. Unexpectedly, the contents of enterobacteria, fungi and Clostridium perfringens decreased at 15 days in all treatments; the decrease in RHP treatment being the sharpest of all. The improvement of the microbiological quality of the diet treated with RHP, although with the same increase in moisture as in A, is explained by the fact that water with addition of RHP is no free water, so it does not increase the a_w and is not available for microbial growth. Furthermore, the content of organic acids, of known effects in microbiological control, would explain the improvements obtained with RHP.

Table 1. Effect of treatment on microbiological quality in diets 1 and 2

PDI (%) and pellet hardness (kg) are shown in Table 2.

The best PDI is obtained with treatment C, regardless of the diet. The addition of moisture in Diet 1 does not alter this PDI. An unexpected effect was the decline of the PDI with increased humidity in Diet 2; this result must be repeated in the light of the discrepancy reported in all the referenced bibliography.

On the hardness, the water-based increase in humidity (A) involves a significant increase in hardness in Diet 2, while increased humidity based on RHP implies a decrease in hardness in Diet 1. These results indicate that an increase in moisture in the feed can be implemented in any kind of formulation based on RHP, but where such an increase is based on water, hardness deterioration in pellets can adversely affect consumption in fattening chicken.

Table 2. Effect of treatment on the durability index (PDI, %) and hardness (kg) in Diets 1 and 2

The results obtained for the digestibility of DM (%), the digestibility of the protein (%) and the gelatinization rate of starch are shown in Table 3. With Diet 1, a slight decrease in DM digestibility is observed in treatment A, compared with treatment C (86.3 vs. 86.5%) whereas when comparing the RHP treatment with treatment C, a slight increase in such digestibility using RHP (86.7 vs. 86.5%) is observed. In contrast, with Diet 2, the increase in humidity results in substantial increases in DM digestibility, being this improvement of much greater magnitude when the hydration occurs on the basis of RHP (85.2 vs. 83.1%).

The increase in humidity improves the digestibility of the protein, especially in Diet 2, in which the use of RHP achieves the largest increase in digestibility. The increase in humidity in the pellets breaks down physical barriers, releasing protein. This effect, coupled with the presence of a surfactant which provides a structural conformation of the protein and a more favorable microenvironment to achieve a greater degradation by digestive enzymes, would explain the improvement in digestibility.

Regardless of the diet, increased humidity due to treatment A leads to a substantial reduction in the gelatinization rate. However, the same increase in humidity due to RHP produced starch gelatinization rate values of 23% (Diet 1) and 4% (Diet 2), higher than those found in Diet C.

Although some authors (Moritz et al., 2002) have reported that the simple increase in the water:starch relationship prior to pelletization significantly improves the starch gelatinization rate, our study found such increase with the addition of RHP, which contributes a surfactant before pelletization.

 The presence of surfactant substances seems to allow a homogeneous integration of water, which has greater capacity to act on the starch, thus improving gelatinization.

Table 3. Effects of the treatment on in vitro DM digestibility (%); in vitro protein digestibility (%) and the starch gelatinization rate in Diet 1 and 2

All the results found concerning the quality of the final product may translate into positive effects on the performance of broiler chicken, as shown by Moritz et al. (2002), Corzo et al. (2011). And there are several papers highlighting, in particular, the effect of the addition of surfactants in the feed on achieving the best production parameters in broiler feed (Günter, 1988; Texton, 1992).

We come to the conclusion that the use of Rehydra-Pro^® improves the microbial quality of the feed, achieves better pellet hardness values and increases in vitro the digestibility of dry matter, protein and, especially, the starch gelatinization rate, resulting in increased nutritional value of pelletized feed.

Boisen S & Fernández JA. 1995. Prediction of the apparent ileal digestibility of protein and amino acids in feedstuffs and feed mixtures for pigs by in vitro analysis. Anim. Feed Sci. Tech. 51:29-43.

Buchanan NP & Moritz JS. 2009. Main effects and interactions of varying formulation protein, fiber, and moisture on feed manufacture and pellet quality. J. Appl. Poult. Res. 18:274-283.

Buchanan NP, Lilly KGS, Gehring CK, y Moritz JS. 2010. The effects of altering diet formulation and manufacturing technique on pellet quality J. Appl. Poult. Res. 19:112-120.

Corzo A, Mejia L. y Loar RE. 2011 Effect of pellet quality on various broiler production parameters. J. Appl. Poult. Res. 20:68-74.

FEDNA. 2008. Normas FEDNA para la formulación de piensos compuestos. de Blas, C., Mateos GG, Rebollar PG. (eds.), FEDNA, Madrid, España, 496 pp.

Günter C. 1988: Einfluss von Emulgatoren auf die Verwen-dung tierischen Fettes von Masthünerküken, de la Hohe Landwirtschaftlische Fakültät der Reinischen Friedrich-Wilheims-Universität zu Bonn. Tesis doctoral de 16 de febrero de 1988.

Hott M, Buchanan NP, Cutlip SE, Moritz JS 2008. The Effect of Moisture Addition with a Mold Inhibitor on Pellet Quality, Feed Manufacture, and Broiler Performance. J. Appl. Poult. Res. 17:262-271.

Medel P, Salado S, Mateos GG, de Blas C. 1999. Processed cereals in diets for early-weaned piglets. Anim. Feed Sci. Technol. 82:145-156.

Moritz JS, Wilson KJ, Cramer KR, Beyer RS, McKinney LJ, Cavalcanti WB y Mo X. 2002. Effect of Formulation Density, Moisture, and Surfactant on Feed Manufacturing, Pellet Quality, and Broiler Performance. J. Appl. Poultry Res. 11:155-163.

Texton JP. 1992. Growth Promotion in Broilers by Copolymer CRL 87-61. J. Appl. Poultry Res. 1:373-381.