D. L. Zanotto

In vitro solubility of meat and bone meal protein with different pepsin concentrations

In vitro protein digestibility of protein sources has been correlated with in vivo digestibility values. However, factors like protein origin, enzyme used and its concentration, pH and processing have been related with the significance of the correlation between the estimates. To address only the enzyme concentration factor, this paper had the objective of testing pepsin at 0.2, 0.02, 0.002 and 0.0002% using the standard AOAC (1995) procedure. Two meat and bone meals (MBM) with low and high crude protein (CP) content were used to determine the coefficient of solubility of CP in pepsin and HCl (CSCPPEPH). Centrifugation was used to establish the nitrogen (N) in the soluble phase, instead of filtration and analysis of N in the residue. The variance analysis and a non-linear asymptotic model were adjusted. The CSCPPEPH under different pepsin concentrations for the two MBM showed higher solubility discrimination with low pepsin concentration. The level of 0.0002% pepsin is better to predict the CP soluble in MBM. This finding implies the assumption that 0.2% pepsin found in the AOAC is not correct for the purpose of determining the range of solubility in high and low CP content in MBM.

Metabolizable energy and amino acids relationships with the soluble fractions of protein and fiber of vegetable feed ingredients

To estimate nutrient and energy digestion with animal from in vitro variables it is necessary to control factors that may interfere on digestion such as: source and concentration of digestor substance, as well as the origin and processing of test ingredients. In this study there were performed five laboratory assays, two with poultry and finally regression equations were established based on variables generated with twelve vegetable ingredients. The results showed that there is greater solubility of proteins with NaOH than with KOH. On average, both alkali produced better discrimination of soluble protein with concentration of 0.02% (range of 68.61%) in relation to a concentration of 0.2% (range of 37.97%). Considering interaction between alkali and concentration, the best discrimination on protein solubility was reached with NaOH at 0.02%. The methods of protein or fiber solubilization together with the chemical analysis showed significant results variation among ingredients and when they were used to estimate in vivo variables they produced good estimates. It was concluded that reliable digestion estimates for energy or amino acids from vegetable feed ingredients could be obtained from in vitro variables, when considering solubilities of protein and fiber with chemical analysis.

Chemical and energy composition of corn harvested with various moisture levels and different drying temperatures to broiler chickens

The experiment was conducted to evaluate the effects of moisture levels at harvest and drying temperatures of corn on its chemical composition and apparent metabolizable energy corrected to zero nitrogen retention (AMEn) to broiler chickens. The corn was harvested with 35%, 25%, 18%, 15.3% and 14.3% of moisture and submitted to drying temperatures of 100, 70 and 40 oC. The moisture levels of 15.3% and 14.3% of corn were not submitted to drying and the last value represented the treatment post-harvesting (60 days after the first harvest). The chemical composition was determined by AOAC (1995) and AMEn assay was carried out by total collection procedure as described by Hill and Anderson (1958) and methodology of Matterson et al. (1965). When the AMEn values were considered on as fed basis, significant differences occured between the treatment of corn no drying and the others. The mean AMEn value was 11.8% less in energy (2864kcal/kg) relative to the highest value (3247kcal/kg).This is due to grain humidity having reached 24% on that treatment caused by natural grain natural re-hydration. When the energy values of corn were changed to dry-matter basis, there were no differences among the treatments. There were no major changes in nutritive value of corn harvested with different moisture levels and submitted to various drying temperatures, compared to expected standards, except the AMEn value (as fed basis) when the corn was no drying.

Influência do estádio de maturação na colheita e temperatura de secagem de grãos de trigo sobre os valores de energia metabolizável aparente corrigida (EMAc) em frangos de corte

An experiment was performed to evaluate the chemical composition values and Apparent Metabolizable Energy corrected for nitrogen excretion (AMEn) of wheat grain harvested at different maturity stage (13, 16, 20 and 30% of humidity levels) and drying temperatures (40, 70 and 100 oC). The grain with 13% of humidity level was considered dried at harvest and was not submitted to drying. The level of 16% of grain humidity at harvesting and the drying temperature of 40 oC provided the highest AMEn wheat value (3326 kcal/kg, as fed basis). Harvesting humidity and drying temperature affected the nutritional value of wheat. It is necessary to know the best maturity stage at harvest and drying temperatures of wheat grains regarding the variability on its nutritive value and inclusion into poultry diets.