Growth performance traits, carcass yield and organ weights

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starches). Corn also contains variable concentrations of other ANFs such as TIs and lectins (Cowieson, 2005). Moreover, it was demonstrated that corn endosperm contain not one but several lectins distributed in protein fractions, namely globulins, zein, and glutelins. Also, corn kernel contained a Lectin with weak haemagglutinating activity as well (Jankovic, Cuperlovic,

& Hajdukovic, 1990).

3.2.4. SDS-PAGE

The seed and experimental diets flours were extracted directly into the denaturing sample buffer for electrophoresis and the protein patterns were visualized on SDS-containing Polyacrylamide gels. Results show that no significant differences could be observed in the distribution or relative abundance of the major protein bands among diets, supporting that all diets possess similar protein content.

Evaluation of the native gel (not shown) shows some degree of variation in broiler diets proteins. This variation may be partially explained by the presence of autoclaved soybeans during different periods into broiler diets, which contain denatured protein, and by the contribution of other animal and vegetal origin ingredients present in all broiler diets. The stained bands represent soybean storage globulins mainly β-conglycinin (7S fraction) and glycinin (11S fraction), products of denaturation of enzyme inhibitors of serine proteases and α- amylase found in soybean and corn, and of others ANFs, such lectins and saponins, phytates, tannins which may remains active in feed even after heat treatment. Typically, protein denaturation begins with unfolding or dissociation of the protein quaternary structure into constituent subunits (the tertiary structures), which in turn associates through intermolecular interaction to form aggregates of irreversibly denatured molecules (Fasina et al., 2003).

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compared with data for chicks fed diets with raw soybean. Heat-processing of soybeans increased the feed efficiency relative to raw soybeans, and the feed efficiency for birds fed diets with autoclaved soybeans for 135 min was significantly higher than that for 0, 105 and 115 min.

Birds performance (body weight, body weight gain and feed conversion ratio) on d 28 of broiler chickens were influenced positively by enzyme supplementation besides the dilution of the substrate and possible interference by other diet components.

In general, literature reports that protease alone or in combination with other enzymes improves nutritive value of poultry diets, however results have been inconsistent. Positive responses to protease supplementation in broiler chickens were observed by Angel, Saylor, Vieira, & Ward (2011) supplementing increasing levels of the enzyme in diets with reductions in CP, lysine, total sulfur amino acids, threonine and metionine, by Yu et al. (2007) using either a mixture of protease and carbohydrase or a single protease, in a corn-SBM broiler diet, and by Cowieson, Singh, & Adeola (2006b) supplementing exogenous xylanase, amylase, and protease in a low nutrient density diet. Conversely, no responses were observed by Olukosi, Cowieson,

& Adeola (2007) who used a blend of xylanase, amylase, and protease. Moreover, pre-feed treatment of SBM with proteases has produced inconclusive responses as well. Ghazi, Rooke, Galbraith, & Bedford (2002) obtained positive responses elicited by protease (isolated from an Aspergillus species) applied under optimum conditions of pH and temperature for the enzyme prior to inclusion of SBM in the broiler diets, whilst Caine et al. (1997) observed no effect on nutrient digestibility when SBM was treated with protease, either as a topical spray or by incubation before inclusion in pigs’ diet. Moreover, Ao, Cantor, Pescatore, Pierce, & Dawson (2010), confirmed that although increasing levels of protease resulted in a linear increase in the release of α-amino N from raw soybean, it did not reduce TI activity.

In this study, it was observed that there was not interaction between heat processing and protease supplementation. It was also noticed that birds supplemented with monocomponent protease (200 mg/kg) were 4% heavier and gained 3.3 % more than those fed the unsupplemented diet, confirming that this enzyme is able to inactivate proteinaceous ANFs

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improving the nutritional value of poultry feeds. Additionally, improvement in FCR was observed in birds fed supplemented diets (Table 4). There was no effect of enzyme supplementation on FI suggesting that the observed performance responses were likely due to changes in the digestibility of nutrients rather than improved digestible nutrient intake.

Moreover, performance impairment increased as level of UA augmented (Table 4), thus UA is an indicator of the presence of TIs in broiler diets evaluated in this study, confirming that loss of the sulfur-rich endogenous proteins as a consequence of hypersecretion of pancreatic enzymes (trypsin and chymotrypsin) caused by TIs would result in growth depression as soy proteins are also deficient in these amino acids (Lajolo & Genovese, 2002).

It was confirmed that exogenous enzymes complement enzymes that birds cannot produce in sufficient quantity by itself, or even reduce the requirement for the endogenous enzyme production, thus making more nutrients and energy available for growth of the chick at early stages of growth (Olukosi et al., 2007). On the other hand, monocomponent protease could hydrolyze proteinaceous ANFs, antigenic proteins and proteins damaged during heat processing. Those ANFs stimulates endogenous losses (mucins, endogenous enzymes etc.), which represent a nutritional cost to the birds, especially in instances where hyper-production occurs (i.e. trypsin inhibitors presence) (Bedford, 2000). Hence, enzyme supplementation could lead to the reduction in the secretion of these endogenous compounds and more digestible nutrients could be available for birds, specially the young ones, which may also explain the effects noted on performance.

Carcass yield improvements occurred when heat-processing time increased. Birds fed diets with soybeans autoclaved for 135 min presented better carcass yield. On the other hand, protease supplementation enhanced carcass yield and diminished abdominal fat deposition (Table 5).

It was observed that consumption of diets containing ANFs led to organ weight alterations. Raw soybean consumption induced an enlargement of the pancreas and duodenum.

Pancreatic secretion is controlled by negative feedback mechanism whereby enzyme secretion is

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inversely related to the level of trypsin present in the small intestine. Thus, when dietary trypsin/chymotrypsin inhibitors reach the duodenum they neutralize the proteases present, this reduction in duodenal protease level is the signal for the release of cholecystokinin (CCK) from the duodenal epithelial endocrine cells that, in turn, after reaching the exocrine pancreas, stimulate the synthesis of large amounts of more serine proteases, and cause pancreatic enlargement (Pusztai, Bardocz, & Martín-Cabrejas, 2004).

The improvement in the nutritional quality of diets trough enzyme supplementation was verified by an attenuation of pancreas and duodenum weight alteration (Table 5). Hence, part of positive effects seen on birds’ performance due exogenous enzyme was mediated through mechanisms such as a reduced mass of gastrointestinal tract segments and/or support organs (i.e. pancreas). Moreover, reduction in specific endogenous secretions allows more energy to be used in protein accretion (Cowieson & Ravindran, 2008).