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Soya bean protein concentrate (SPC) with two particle sizes were evaluated on extrusion parameters, kibble formation, digestibility and palatability of dog foods. Eight diets were extruded: PBM-control diet based on poultry by-product meal (PBM); GM-a diet in which corn gluten meal (GM) replaced 45% of the diet protein; cSPC15%, cSPC30% and cSPC45%-diets in which SPC of coarse particle size (600 μm) replaced 15%, 30% and 45% of the diet protein; and sSPC15%, sSPC30% and sSPC45%-diets in which SPC of small particle size (200 μm) replaced 15%, 30% and 45% of the diet protein. The digestibility of nutrients was evaluated for the PBM, GM, cSPC45% and sSPC45% diets, using six dogs per food. The PBM, GM and cSPC45% diets were compared for palatability. Data were submitted for analysis of variance, and the means were compared by polynomial contrasts or Tukey's test (p < .05). The cSPC increased the specific mechanical energy (SME) application, extrusion temperature and pressure linearly, resulting in lower kibble density and higher expansion and starch gelatinization (SG) (p < .01). When comparing the PBM, GM, cSPC45% and sSPC45% diets, higher SME, extrusion temperature and pressure, SG and kibble expansion were verified for the cSPC45% diet (p < .05). The DM, fat and crude protein digestibility were similar among diets. Faecal pH, ammonia and lactate did not differ, demonstrating that the removal of oligosaccharides and soluble non-starch polysaccharides of SPC produces an ingredient with mostly non-fermentable fibre. Dogs preferred the PBM to the GM diet (p < .05), but consumed the PBM and cSPC45% foods equally. In conclusion, SPC exhibited good extrusion functionality, favouring kibble expansion and SG, with high digestibility, similar to that of PBM. The removal of soluble compounds from soya beans resulted in an ingredient with low fermentable fibre content, which did not alter faecal formation or characteristics.

Three experiments were conducted with broiler chickens to evaluate the effects of digestible total sulphur amino acid (TSAA) on their performance at three different phases of starter (1-14 d), grower (15-28 d) and finisher (29-42 d). The measured traits included: average daily gain (ADG), feed intake, feed conversion ratio (FCR), carcass protein, body lipid (BL), feather weight gain, carcass plus feather protein, carcass TSAA deposition and nitrogen excretion (NE). A dilution technique was used to create seven diets (with eight replicates) increasing the TSAA content from 2.5 to 9.04 g/kg of diet for starter, 2.26 to 8.14 g/kg of diet for grower and 2.08 to 7.5 g/kg of diet for finisher. Data measured were imported to neural networks to predict the measured traits in response to dietary and intake levels of TSAA and find the optimal levels of TSAA that lead to the desired responses. Optimization results showed decreases in optimal dietary TSAA values with increasing age for all traits, while reverse was observed for intake values and requirements were increased as birds aged. The highest TSAA requirement (7.95, 7.2 and 6.6 g/kg and 283, 585 and 1150 mg/bird per d for starter, grower and finisher, respectively) were achieved for minimum BL and lowest (5.8, 5.2 and 4.9 g/kg and 201, 444 and 873 mg/bird per d for starter, grower and finisher, respectively) were suggested for minimum NE. Based on intake models, the optimal TSAA values for minimum FCR in phases 1-3 were 283, 585 and 1150 mg/bird per d while maximum ADGs were achieved with 201, 444 and 873 mg/bird per d of TSAA.

This study aimed to estimate the essential amino acid profile and the ideal ratio for the maintenance of poultry by deletion method. A nitrogen balance (NB) trial was conducted using 198 adult roosters, housed individually in metabolic cages. The treatments were 33 purified diets being 11 diets with an amino acid mixture providing high protein intake of 500 mg N/BWkg (0.75) per day, 11 diets providing medium protein intake of 250 mg N/BWkg (0.75) per day (in each diet, one amino acid tested was diluted 50%) and 11 diets providing low protein intake of 125 mg N/BWkg (0.75) per day (made by omitting the amino acid tested). Each treatment had six replicates. After 48 h of fasting receiving water plus sucrose, the roosters were fed 40 g of the diets by tube once a day for 3 days. The excreta were collected within 72 h after the first feeding. The diets and excreta were analysed for nitrogen content. For each amino acid studied, a linear regression was fitted by NB and amino acid intake (AAI). The maintenance requirements were estimated as the AAI to maintain the NB equal to zero. The daily amino acid requirements for maintenance were estimated to be Lys 11, Met 29, Thr 23, Trp 5, Arg 50, Val 29, His 6, Gly 54, Phe 49, Leu 78 and Ile 21 mg/BWkg (0.75) per day. Therefore, the amino acid ratio for maintenance was concluded to be Lys 100, Met 276, Thr 220, Trp 48, Arg 467, Val 275, His 60, Gly 511, Phe 467, Leu 735 and Ile 198% independent of the scale. The essential amino acid profile and the ideal ratio for the maintenance of poultry estimated in this study contributed to improve the factorial model for estimating essential amino acid requirements for poultry.