Prececal amino acid digestibility of soybean cake in fast- and slow-growing broiler chickens

Efficiency of Soybean Products in Broiler Chicken Nutrition

Simple Summary

The studies show how replacing soybean meal with soybean expeller cake or extruded full-fat soybean in feed rations for broiler chickens affects rearing results (weight gain, intake and conversion of feed), carcass composition (dressing percentage, musculature, fattens) and meat quality (physical properties: pH, colour, water holding capacity; the chemical composition: basic components, fatty acids and organoleptic value: flavour, tenderness, palatability and juiciness). Based on the results the use of soybean expeller cake in broiler chicken starter/grower diets can be recommended as it allowed for obtaining the best production and slaughter results. However, from the point of view of the human diet, extruded full-fat soybean should be suggested since it best modified the lipid fraction of muscles.

Abstract

The study aimed to determine the overall effect of replacing soybean meal completely with soybean expeller cake or extruded full-fat soybean in feed rations for broiler chickens on their carcass composition and meat quality. The experiment involved one hundred and twenty Ross 308 broiler chickens randomly allocated to three equinumerous groups (SBM, SEC, EFS). Each group was divided into five subgroups—each consisting of eight birds of both sexes (1:1). From Day 1 to Day 21 of life the birds were fed with loose starter rations, and from Day 22 to Day 42 they were fed grower rations based on a wheat meal, protein products and mineral and vitamin admixtures. The experimental factor was a protein raw material comprising: SBM group—soybean meal from GM (genetically modified) seeds, SEC—soybean expeller cake from n-GM seeds, and EFS—extruded full-fat soybean from n-GM seeds. The experimental diets were isocaloric and isonitrogenous. It was demonstrated that replacing soybean meal with SEC or EFS in feed rations for broiler chickens led to a significant (p < 0.05) weight gain on Day 42 of rearing by 4.57% and 2.88%, respectively. The chickens fed diets with EFS had worse (more than 4.14%) feed conversion rate (FCR) in comparison to the others (p < 0.05). Broiler chickens from the SBM and SEC groups showed a higher share of breast and leg muscles (by 4.74% and 7.54%) and a lower share of abdominal fat (by 31.1%) and skin with subcutaneous fat (by 18.8% and 13.4%) in comparison with birds from the EFS group (p < 0.05). The highest content of intramuscular fat with the best fatty acids profile was determined in the muscles of birds fed with diets containing EFS, while the muscles of chickens receiving SEC scored the highest. The results provide grounds for recommending SEC in broiler chicken nutrition as it allowed for obtaining the best production and slaughter results, whereas—from the point of view of the human diet—EFS should be recommended since it best modified the lipid fraction of muscles.

Influence of feed provisioning prior to digesta sampling on precaecal amino acid digestibility in broiler chickens

A regression approach was applied to determine the influence of feed provisioning prior to digesta sampling on precaecal (pc) amino acid (AA) digestibility in broiler chickens. Soybean meal was used as an example test ingredient. Five feed-provisioning protocols were investigated, four with restricted provision and one with ad libitum provision. When provision was restricted, feed was provided for 30 min after a withdrawal period of 12 h. Digesta were sampled 1, 2, 4 and 6 h after feeding commenced. A diet containing 300 g maize starch/kg was prepared. Half or all the maize starch was replaced with soybean meal in two other diets. Average pc digestibility of all determined AA in the soybean meal was 86% for the 4 and 6-h protocols and 66% and 60% for the 2 and 1-h protocols, respectively. Average pc AA digestibility of soybean meal was 76% for ad libitum feed provision. Feed provisioning also influenced the determined variance. Variance in digestibility ranked in magnitude 1 h > ad libitum > 2 h > 6 h > 4 h for all AA. Owing to the considerable influence of feed-provisioning protocols found in this study, comparisons of pc AA digestibility between studies applying different protocols prior to digesta sampling must be treated with caution. Digestibility experiments aimed at providing estimates for practical feed formulation should use feed-provisioning procedures similar to those used in practice.

Effect of particle size distribution of maize and soybean meal on the precaecal amino acid digestibility in broiler chickens

1. Herein, it was investigated whether different particle size distributions of feed ingredients achieved by grinding through a 2- or 3-mm grid would have an effect on precaecal (pc) amino acid (AA) digestibility. Maize and soybean meal were used as the test ingredients. 2. Maize and soybean meal was ground with grid sizes of 2 or 3 mm. Nine diets were prepared. The basal diet contained 500 g/kg of maize starch. The other experimental diets contained maize or soybean meal samples at concentrations of 250 and 500, and 150 and 300 g/kg, respectively, instead of maize starch. Each diet was tested using 6 replicate groups of 10 birds each. The regression approach was applied to calculate the pc AA digestibility of the test ingredients. 3. The reduction of the grid size from 3 to 2 mm reduced the average particle size of both maize and soybean meal, mainly by reducing the proportion of coarse particles. Reducing the grid size significantly (P < 0.050) increased the pc digestibility of all AA in the soybean meal. In maize, reducing the grid size decreased the pc digestibility of all AA numerically, but not significantly (P > 0.050). The mean numerical differences in pc AA digestibility between the grid sizes were 0.045 and 0.055 in maize and soybean meal, respectively. 4. Future studies investigating the pc AA digestibility should specify the particle size distribution and should investigate the test ingredients ground similarly for practical applications.